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The bike that slowtwitch built

 

 


23

May 12, 13 17:22

Post #1 of 86 (12168 views)
The bike that slowtwitch built Quote | Reply

http://oi44.tinypic.com/35icg3n.jpg

this is my vision of the ultimate sub 10 degree yaw triathlon (50kph) bike built much by the knowledge of slowtwitch forums. Its been a fun project and I'm up for critique and hopefully a couple compliments too!

Ok so I'll explain it front to back.

single dura ace bar end shifter
vision aero brakes on bar ends
s bends with bull horns removed
aero nose cone tapering from a rounded 1 inch front to 1 .5 inch peak width at head tube and tapering into a smooth airfoil. Totaling a 23 cm deep headtube
tri rig aero brake concealed in nose cone
650 jetstream fork pulling air off the 650 hed 3 deep clinch, vitt open corsa 20 latex tube, tire rim smothed with silicone front n back
aero nutrition container behind stem
front wheel drafts off the 650 tube container
soon to come speed aero skewers
bottom bracket box for co2 levers and valve inflator
fsa neo pro 170mm crank no front mech speedplay pedals
adamo saddle
tailbox for 700 tube, bottom bracket box and esp tail box create tom as splitter effect with bulge disk and 23mm conti gp 4000
hidden is sleek simkins egg brake tucked behind bb.
ten speed dura ace.
carefully followed all usat rules.
23 cm of aero bar drop but 5 due to rotating on front 650 not changing angles. plus adamo and 170 cranks, hip is nice and proper.
soon to come aero derail pulleys.
hope you like


Herbert

May 12, 13 17:27

Post #2 of 86 (12136 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Oh my. Holy batman.





J_R

May 12, 13 17:30

Post #3 of 86 (12117 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Not sure where to start. Looks pretty badass. Is it legal?


Prince_Denmark

May 12, 13 17:33

Post #4 of 86 (12056 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

bravo.


lowcel

May 12, 13 17:39

Post #5 of 86 (11965 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Very cool but I have to ask, how is it in cross winds?


hillier99

May 12, 13 17:50

Post #6 of 86 (11878 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

We need more pics!

Side view, front and rear. What's the leading edge of the front wheel cut out look like?

Nice work.
Brad


----------------------------------------------------------
3SIXTY5cycling.com - Full Carbon Clinchers


bricklayer

May 12, 13 17:50

Post #7 of 86 (11876 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Your seat is too high.


J_R

May 12, 13 17:55

Post #8 of 86 (11841 views)
Re: The bike that slowtwitch built [Herbert] [In reply to] Quote | Reply

Kudos on promoting to a sticky thread Herbert. Totally agree that it is well deserved.

I think we need pics from more angles though!!


(This post was edited by J_R on May 12, 13 17:55)


Philosoraptor

May 12, 13 18:05

Post #9 of 86 (11773 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Did you build the frame from scratch or is it a factory frame with bits bonded to it?


23

May 12, 13 18:09

Post #10 of 86 (11757 views)
Re: The bike that slowtwitch built [J_R] [In reply to] Quote | Reply

as far as I can see it should be usat legal. follows all rules


23

May 12, 13 18:11

Post #11 of 86 (11740 views)
Re: The bike that slowtwitch built [lowcel] [In reply to] Quote | Reply

the frame shouldn't be much diff than any deep super bike. if the wind looks troublesome just switch up wheel choices.


23

May 12, 13 18:13

Post #12 of 86 (11727 views)
Re: The bike that slowtwitch built [bricklayer] [In reply to] Quote | Reply

it just looks like the seat is too high, but I sit on the very nose where the saddle slopes down and the hight is just perfect on closer inspection :)


23

May 12, 13 18:15

Post #13 of 86 (11715 views)
Re: The bike that slowtwitch built [Philosoraptor] [In reply to] Quote | Reply

it is a factory frame with aero containers integrated into the frame


severinj

May 12, 13 18:23

Post #14 of 86 (11663 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

this turned my brain into scrambled eggs. Amazing.


23

May 12, 13 19:01

Post #15 of 86 (11495 views)
Re: The bike that slowtwitch built [hillier99] [In reply to] Quote | Reply

http://i42.tinypic.com/30mthli.jpg
http://i42.tinypic.com/2lst95e.jpg
http://i43.tinypic.com/2yo72g8.jpg

im sorry for links dont know how to post pic and sorry for nudity in third pic.


hedgefund

May 12, 13 19:01

Post #16 of 86 (11493 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

You have demonstrated amazing work ! I would like to borrow it and fit with double disc to break a TT record. Is it for rent?


Herbert

May 12, 13 19:17

Post #17 of 86 (11425 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

A couple more







bujayman

May 12, 13 19:32

Post #18 of 86 (11357 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

What factory frame?


23

May 12, 13 20:21

Post #19 of 86 (11211 views)
Re: The bike that slowtwitch built [bujayman] [In reply to] Quote | Reply

it is an older carbon felt b2. not very aeroitself but a perfect base because of the horizontal dropouts , hidden rear brake , shape already started to follow the front and rear wheel some, and most importantly very narrow with a 1 inch headtube instead of the new 1 1/8


JTolandTRI

May 12, 13 20:22

Post #20 of 86 (11209 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Stunning. How does it ride?


Jack Toland
Blog | Twitter @JTolandTRI | Coached by Accelerate3


desert dude

May 12, 13 20:25

Post #21 of 86 (11202 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Totally Bad Ass!


Brian Stover
Accelerate3 Coaching :: @accelerate3 :: Like us on Facebook
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LostNTransition

May 12, 13 20:45

Post #22 of 86 (11150 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

This is the first time I've seen brakes out on the aero bars (you don't have anywhere else to put them though).

It seems like it might be a bit hard to stop, not that you would want to when riding that beauty anyway.


23

May 12, 13 21:11

Post #23 of 86 (11091 views)
Re: The bike that slowtwitch built [JTolandTRI] [In reply to] Quote | Reply

it rides surprisingly well. that said ive only ridden it once around the neighborhood so more riding is needed. At first I kept sitting up to brake only to find they weren't there and had to go back down to brake. or just reach out with one hand on right brake, left hand on mini base bar, how cornering worked best for me. I really dont find stearing, cornering, u turning or braking an issue. I wouldn't want it for a crit haha, but a tri orr tt will be just fine once familiar with it. it is a long bike with a long stem, so it corners nice and sweeping, helping it feel more stable.


23

May 12, 13 21:19

Post #24 of 86 (11074 views)
Re: The bike that slowtwitch built [desert dude] [In reply to] Quote | Reply

Im in college station where we have a low speed wind tunnel. im looking into getting it in there and compare it to some university tri team members both with just bikes and riders. Ive been in the tunnel with John Cobb before there and think it would be cool if he got involved, so I'll be contacting him as well.


iluv83vettes

May 12, 13 22:53

Post #25 of 86 (10928 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

It would look better with zebra stripes ...


mschole

May 13, 13 1:55

Post #26 of 86 (7824 views)
Re: The bike that slowtwitch built [LostNTransition] [In reply to] Quote | Reply

LostNTransition wrote:
This is the first time I've seen brakes out on the aero bars (you don't have anywhere else to put them though).

It seems like it might be a bit hard to stop, not that you would want to when riding that beauty anyway.
Natascha Badmann's bike had no base bar and a twist brake on the aerobars I believe?

---------------------------------
http://smaryka.blogspot.com


davetallo

May 13, 13 5:46

Post #27 of 86 (7672 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Lovely! But replace the fork with a Blackwell Time Bandit.


leegoocrap

May 13, 13 6:21

Post #28 of 86 (7612 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Very cool. Would love to see some numbers on this thing :P

My Blog - http://leegoocrap.blogspot.com
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Barchettaman

May 13, 13 7:18

Post #29 of 86 (7514 views)
Re: The bike that slowtwitch built [leegoocrap] [In reply to] Quote | Reply

Good grief, what an utterly awesome machine.
Beauty & danger in equal measure.

-------------------------------
´Get the most aero and light bike you can get. With the aero advantage you can be saving minutes and with the weight advantage you can be saving seconds. In a race against the clock both matter.´

BMANX


devashish_paul

May 13, 13 10:11

Post #30 of 86 (7211 views)
Re: The bike that slowtwitch built [Herbert] [In reply to] Quote | Reply

Herbert wrote:
Oh my. Holy batman.



Not quite the same, but to some degree the middle part of the bike reminds me of the old Trimble frames. I couldn't find any images around google that are that great, but here is one:




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Whiteface Hill Climb + Epicman Lake Placid 3k/180k/21k June 5/6 2014, Epicman Tremblant 10k/260k/42.2k 11-13 July 2014


karlaj

May 13, 13 11:30

Post #31 of 86 (7082 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

It's missing lights:

First frame with a negative CdA? Awesome work. -J

----------------------------------------------------------------
Life is tough. But it's tougher when you're stupid. -John Wayne


TonyStark

May 13, 13 12:51

Post #32 of 86 (6968 views)
Re: The bike that slowtwitch built [Herbert] [In reply to] Quote | Reply

I love the fact that the door in the background needs to be painted and the lawn has been completely neglected. Makes me feel a little less guilty for blowing off similar household duties to train.

-----------------
Dale Stephanos (Formerly PappaD)



santa777

May 13, 13 14:08

Post #33 of 86 (6843 views)
Re: The bike that slowtwitch built [PappaD] [In reply to] Quote | Reply

No need for a water bottle,,

BECAUSE IT'S SO FAST!

I would love to see this thing moving.


BCtriguy1

May 13, 13 18:32

Post #34 of 86 (6586 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

The only thing that bike needs is a giant ST logo on the rear disk.

And a front disk, just for kicks =).

Well done. Seriously, that thing looks like a beast and would turn a lot of heads at a TT or tri.


Bmanners

May 13, 13 18:36

Post #35 of 86 (6579 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

very cool!

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sailnfast

May 13, 13 19:43

Post #36 of 86 (6509 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Impressive. What's it weigh?


chadman_98126

May 13, 13 22:18

Post #37 of 86 (6413 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

wow. apologies in advance, but there is virtually nothing aero about this bike. the wheels and the fork perhaps, but the frame is an unmitigated disaster from the top tube on down. the top tube should be ovoid anywhere rear of the head tube airfoil - full stop. and if the attempt here is to develop negative drag, airfoils of no more than 15%-20% should be considered - e.g. NACA 0015 or 632-015 - or even better, truncated Kammtail airfoils (e.g. a truncated NACA 0020 with a 3:1 aspect ratio) which will be much more forgiving in crosswinds, yet just as slippery and still generate forward thrust. furthermore, the rounded front on the head tube and elsewhere on the bike likely experiences complete flow separation well before its apex (at about 82 degrees) creating pressure drag and turbulent airflow. moreover, the undulating sides of the frame are simply creating skin friction and/or flow separation and pressure drag - you'd be better with nothing at all. and that tail? sorry.

the best thing you might be able to do to repair some of this is install 'trip wires' -- around 0.5mm-1mm thick should do it - the entire vertical length of the head tube and anywhere there's a forward facing tube surface. place the 'trip wires' on either side roughly 30-45 degrees away from center axis -- this may at least re-attach the airflow to the sides of the frame.

the other option is to rip it all out and order truncated NACA 0020 foam cores from someone like Flying Foam (http://www.flyingfoam.com) and then cover them with a fiber composite layer.

then of course there's the reduced trail in the fork by going 'funny' with the 650c on the front. no issue going to a 650c, but important to go with a 650c wheel in the rear as well. that'll drop the bottom bracket to just above the UCI/USAT minimum of 240mm (hey, you're already about half-way there...), and by re-introducing the correct amount of trail in the front fork, you'll also get some control back (all the more so since the bull bars have been cut off...)


(This post was edited by chadman_98126 on May 14, 13 0:18)


chadman_98126

May 13, 13 22:24

Post #38 of 86 (6408 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

and just realized that's probably a 650 fork with that 650 wheel, correct? if so, the front of the frame has already been dropped around 51mm and the trail on the front fork will be just about shot.


(This post was edited by chadman_98126 on May 14, 13 6:20)


btmoney

May 14, 13 0:32

Post #39 of 86 (6340 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Holy shit I love it.


cyclenutnz

May 14, 13 1:43

Post #40 of 86 (6312 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

Going from a 368mm 700C fork to a 340mm 650C fork I get a change in BB drop from 70mm to 84mm for the Felt Geo. HTA from 73 to 75.1. Trail from 60 to 48.

I agree with all your points, I'm just pointing out that the geo change isn't quite as bad as you think.


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runido

May 14, 13 4:16

Post #41 of 86 (6242 views)
Re: The bike that slowtwitch built [cyclenutnz] [In reply to] Quote | Reply

cool


chadman_98126

May 14, 13 6:19

Post #42 of 86 (6154 views)
Re: The bike that slowtwitch built [cyclenutnz] [In reply to] Quote | Reply

plus another 25.5mm drop in the fork for the smaller 650c wheel... (so a quick SWAG puts the trial in the 36mm range or less. twitchy.)


(This post was edited by chadman_98126 on May 14, 13 6:27)


Rambler

May 14, 13 6:55

Post #43 of 86 (6107 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

So maybe the Trimble comparison is appropriate?


23

May 14, 13 7:30

Post #44 of 86 (6067 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

First off I would like to say thank you. Although the compliments make me feel warm and fuzzy, the reason I posted it here is because slowtwitch is notorious for being brutally honest and over analyzing every aspect. There are alot of smart people here with constructive criticism.So thank you for being first.

The bike was designed for zero degrees of yaw. I have a feeling it will stall dramatically at a certain increasing yaw angle. In my original post I said sub 10 yaw assuming that it would be such a bullet at angles approaching zero that it would be faster avg out to ten still. Pure speculation. From a yaw perspective the oviod top tube makes perfect sense and is going into my mental data base.

As far as far as the airfoils go the reason they are so deep is so that the diminishing angle is minimal, should be deeper more effective head on airfoils than any bike. You cant make a bike that is best at everything, this one uses super deep airfoils at the expense of catching more crosswind. You are correct saying Kamm tails would help this, but you are wrong on saying it is just as slippery. A Kamm tail is merely a compromise on a longer more optimized full airfoil and is NOT faster at discussed yaw. Its a specialized bike and not for an ag going 17 mph in brutal crosswinds.

How else would you make a leading edge of a nosecone ( practically the only vertical tube)? all bikes i know of have a rounded leading edge. This is more effective at yaw. A pointy nose would be terrible at anything other than zero yaw, but awesome at zero. I compromised creating a reduced rounded one inch nose tapering up to the peak with of the headtube. creates a nice long oval shaped nose.

the tailbox and bottom bracket box only smooths airflow by reducing frame gaps secondarily. They theoretically use the splitter effect along with the disc wheel to reduce clashing turbulent wind from the body. Yes the containers do undulate VERY slightly as you look down the bike. ie the bottom bracket box is slightly narrower at the center of it than the peak of the tube diameters. yes, perfectly flush would be optimized (future upragde?) but to say that it hurts aerodynamics is similar to saying the much greater undulation of the bulge on a disk wheel makes it worthless because of all the skin friction and pressure drag it created.

im excited to get it in the tunnle to get a more worthwhile view of the bike than speculation.

The steering geometry is something I did quite alot of research before hand. Yes, it makes the steering more sensitive to reduce trail. Put on a 150 stem it smooths it out. Im not a roadie so cant compare it to a 13 lb super agile crit bike, but doesnt seem like anything different than before for steering. I took it over dips around curves and 180 turn arounds. Is steering optimized, probably not, but it works perfectly fine for tt and tris. btw putting the only way to have a 650 wheel is with the 650 fork. putting a 650 on the back would be impossible if u want brakes, and would defeat the purpose of a front 650 at all.

This was built with some hand tools and a box of junk on my gf back porch. This is my first 'prototype' and would love to continue refining it. Especially increasing its effectiveness over wider yaw. I appreciate the criticism! please keep it coming.



23

May 14, 13 7:52

Post #45 of 86 (6047 views)
Re: The bike that slowtwitch built [Rambler] [In reply to] Quote | Reply

maybe so haha, however I did study the Trimble alot before I built. The Trimble was a bullet without rider in the tunnel. The opposite with the rider. similar to catching more water with very slightly spread fingers in swim pulling, the proximity of the leg to the frame mass created additional drag. In proper tt form the knees are in at the top tube. This leaves the largest leg frame gap at the crank and the legs approach the frame closer as you move up. I specifically avoided the problems of the Trimble by placing the bottom bracket box low for appropriate leg spacing for air to flow proper (like the p4) and placed it angled further back to reduce crosswind pressure on front and increase splitter plate effect toward back. so theoretically I eliminated the Trimble problem.


chadman_98126

May 14, 13 8:57

Post #46 of 86 (5943 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

assuming the airfoils are symmetric and laminar - they appear to have about a 8:1-10:1 aspect ratio, they will likely never stall. they will generate lift. lots of it.


elduderino2412

May 14, 13 11:47

Post #47 of 86 (5739 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Nice looking rig. Crosswinds might be pretty frustrating though.


chadman_98126

May 14, 13 13:00

Post #48 of 86 (5641 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

and rather than just throw pot shots at this, here's a quick listing of max angle of attack for different lambda, where lambda is the ratio of rider speed to windspeed.

lambda = 2, max angle of attack = ~27 degrees
lambda = 3, max angle of attack = ~16 degrees
lambda = 4, max angle of attack = ~11 degrees

so for a rider traveling along a TT course at 40kmh with a windspeed of 10kmh, the absolute maximum angle of attack they will ever see is about eleven degrees and the frame airfoils will never stall. not even close. conversely, the rider will be constantly being pushed to the side except for that short moment that they are facing directly upwind and downwind. everything else is pure lift (i.e. a near constant side force, never stall)

along those lines, NACA 0015 or 0018 series airfoils (with an aspect ratio between 5.55-6.67) are pound for pound the best airfoils for upwind, downwind and crosswind performance. period.

(and yes, I develop wind turbines...)


(This post was edited by chadman_98126 on May 14, 13 13:24)


bob_nohope

May 14, 13 13:36

Post #49 of 86 (5587 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

23 wrote:
From a yaw perspective the oviod top tube makes perfect sense and is going into my mental data base.

Ha ha love that line: Translation -"I hear you, but I'm going to do fuck all about it!"

i have a feeling I'll be using that myself


cyclenutnz

May 14, 13 13:45

Post #50 of 86 (5575 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

chadman_98126 wrote:
plus another 25.5mm drop in the fork for the smaller 650c wheel... (so a quick SWAG puts the trial in the 36mm range or less. twitchy.)

Funnily enough I never included the ability to change wheel size in the fork length change effect calculator - I was just thinking of swapping different length forks with the same wheel size.

Adding in the effect that you've noted gives:
HTA: 73 becomes 77.3
Trail becomes 34
BB drop 100

That could be a bit exciting.


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brown_dog_us

May 14, 13 13:48

Post #51 of 86 (5252 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Sweet!


chadman_98126

May 14, 13 14:23

Post #52 of 86 (5218 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

23 wrote:


As far as far as the airfoils go the reason they are so deep is so that the diminishing angle is minimal, should be deeper more effective head on airfoils than any bike. You cant make a bike that is best at everything, this one uses super deep airfoils at the expense of catching more crosswind. You are correct saying Kamm tails would help this, but you are wrong on saying it is just as slippery. A Kamm tail is merely a compromise on a longer more optimized full airfoil and is NOT faster at discussed yaw.


This is not always the case - carefully designed, truncated airfoils can result in lower drag, even at zero yaw. on a properly designed Kammtail, the geometry forms smaller vortices on the blunt trailing edge that are shed quickly, which in turn can result in a lower Cd than the original airfoil. with yaw greater than zero, the delta between the truncated Kammtail and the original airfoil is even more pronounced.


(This post was edited by chadman_98126 on May 14, 13 17:57)


Bretom

May 14, 13 14:33

Post #53 of 86 (5208 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

You need to realize when something is so damn awesome that it transcends criticism. This is the Meatloaf of tribikes.



"Are you sure we're going fast enough?" - Emil Zatopek


greatwhite

May 14, 13 17:43

Post #54 of 86 (5129 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

coolest bike I've seen in a long time

http://www.onelesshiker.com


chadman_98126

May 14, 13 18:21

Post #55 of 86 (5121 views)
Re: The bike that slowtwitch built [cyclenutnz] [In reply to] Quote | Reply

cyclenutnz wrote:

Adding in the effect that you've noted gives:
HTA: 73 becomes 77.3
Trail becomes 34
BB drop 100
That could be a bit exciting.


on a 98cm wheel base the 52mm drop with the smaller 650c wheel and fork results in a 3 degree increase in the HTA and with a 41 cm chain stay the BB drops about 22mm. so with a typical BB ground clearance of 268mm you end up with a BB clearance around 242-246mm - just on the edge of the 240mm UCI/UASC/USAT minimum. running instead two 650c wheels on a 700c frame you end up with the about the same frame drop (25.5m vs. 22mm) that "23" is trying to achieve, but with a bike that still handles properly and is actually aero. install a pair of Tektro R725 brakes (or a set with a similar 24-26mm drop) and you're pretty much set.

QED.


(This post was edited by chadman_98126 on May 14, 13 18:24)


cyclenutnz

May 14, 13 19:23

Post #56 of 86 (5090 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

You need to use x,y of bottom of the HT for the radius (assuming your swag was based on s=r*theta) rather than the WB. The frame pivots on the rear axle as it loses elevation from the fork/wheel assembly.

Which is 782mm on a 54 Felt B2. That with a 59 shortening (31mm on wheel, 28mm on fork) gives the figures above.

But I still fail to see the advantage of bringing 650c into the picture at all - fewer wheel choices (and more importantly - tyres).


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chadman_98126

May 14, 13 20:16

Post #57 of 86 (5063 views)
Re: The bike that slowtwitch built [cyclenutnz] [In reply to] Quote | Reply

Certainly. In the absence of the head tube to rear axle radius, the wheelbase is a pretty reasonable approximation. given that the drop from the smaller wheel size is 25.5mm (622-571)/2, and all things being equal, the fork being roughly 25.5mm shorter, the rotation of the bike is roughly 3 degrees or ATAN (51/980), in the case of a 98cm wheelbase.

As for the 650c, certainly the 700c might be preferable - there are advantages to both, I was simply suggesting that "23" needs to look into keeping the wheel sizes the same, either 700 or 650, but not both and not with a shorter front fork - a 32-34mm trail on a TT bike with the bull bars cutoff seems a bit, um, imprudent.

btw: I believe the new P5 drops the bottom bracket 12-15mm. I believe it's still in the 250mm range, but they're definitely making the move to lower the overall profile of the frame. :-)

best.


(This post was edited by chadman_98126 on May 14, 13 20:48)


chadman_98126

May 14, 13 20:35

Post #58 of 86 (5052 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

btw: "23" you should give some serious consideration to 'roughing up' the outer perimeter of those tires to prevent flow separation - think dimples on a zipp wheel.

seeing as this is DIY, something to consider would be perforated vinyl film (similar to what they use for one-way printed window signs on stores and buses) with either 30/70 or 50/50 light permissibility. in the case of the disk wheel, a concentric ring covering the outer bulb portion would do nicely (but keep the center circle inside the bulb perimeter smooth and flat). and the case of the HED tri-spoke, basically the entire surface (outer rim, spokes, etc.). the vinyl is pliable and flexible enough that you might be able to overlay the entire side of the tri-spoke with one piece. and the diameter of the perforated holes is around 1.6-2.0mm so just about the right size (and depth) for a dimple.


(This post was edited by chadman_98126 on May 14, 13 20:39)


damon_rinard

May 15, 13 3:47

Post #59 of 86 (4956 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

Hi chadman,

In theory, covering a tri spoke with dimple film could be interesting.
In practice, it's been in the wind tunnel.
Unfortunately I'm not allowed to quote results.
But the tri spokes in our house are clean and smooth.

Cheers,

Damon Rinard, just me for now.


23

May 15, 13 5:54

Post #60 of 86 (4883 views)
Re: The bike that slowtwitch built [cyclenutnz] [In reply to] Quote | Reply

In my mind the 650c front and 700c rear has nothing at all to do with bike aerodynamics, but body aerodynamics. Sure it dropped the bb to near the usat minimum and that is nice. Its about changing your body position. It drops your aerobars near 5cm for 'free' without any hip angle closure. its much more important to reduce the profile of the rider than drop the whole system a bit with no frontal profile change.


damon_rinard

May 15, 13 6:18

Post #61 of 86 (4865 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

Hi 23,

That was my thinking when I made the Kestrel track bike Sean Wallace rode to the silver medal in the 1992 pursuit world championships. We did what you did: dropped in a 650C front wheel and fork. At the time I did the math, and like cyclenutz and others, found about 3 degrees of rotation everywhere: seat angle, head angle, top tube, everything. In this case I also jacked up the back (packaging the conversion dropouts made that automatic) and ended up with ~4 degrees.

Yes, trail was greatly reduced, but Sean said he liked it, and in practice it was never a problem for him. Not that I would design a bike that way on purpose, but it wasn't dangerous under the right rider.

Cheers,

Damon Rinard, just me for now.


chadman_98126

May 15, 13 6:23

Post #62 of 86 (4864 views)
Re: The bike that slowtwitch built [damon_rinard] [In reply to] Quote | Reply

damon_rinard wrote:
Hi chadman,

In theory, covering a tri spoke with dimple film could be interesting.
In practice, it's been in the wind tunnel.
Unfortunately I'm not allowed to quote results.
But the tri spokes in our house are clean and smooth.

Cheers,


nice! I'm on a total 'turbulence tripping' tear of late and have been looking at some innovative ways to handle bluff bodies, so my inclination is to 'rough it up' when I see a smooth bluff body. [note: dimples seem like more of a last resort for turbulence tripping and probably only make sense in the case of a golf ball, and maybe on the outer rim of a wheel, maybe. case in point, I kind of chuckle when I see the dimples on the front of the new Garneau helmets...]


btw Damon: what do you take of this frame design? when I first clicked on the thread I was excited to see something 'crowd-sourced' by the slow-twitch community. not exactly what I expected to see.


(This post was edited by chadman_98126 on May 15, 13 6:39)


chadman_98126

May 15, 13 6:38

Post #63 of 86 (4854 views)
Re: The bike that slowtwitch built [damon_rinard] [In reply to] Quote | Reply

damon_rinard wrote:
Hi 23,

That was my thinking when I made the Kestrel track bike Sean Wallace rode to the silver medal in the 1992 pursuit world championships. We did what you did: dropped in a 650C front wheel and fork. At the time I did the math, and like cyclenutz and others, found about 3 degrees of rotation everywhere: seat angle, head angle, top tube, everything. In this case I also jacked up the back (packaging the conversion dropouts made that automatic) and ended up with ~4 degrees.

Yes, trail was greatly reduced, but Sean said he liked it, and in practice it was never a problem for him. Not that I would design a bike that way on purpose, but it wasn't dangerous under the right rider.

Cheers,

34-36mm trail for a track bike is a quite a bit different than an open air TT on public pavement, no? and without bull bars??


damon_rinard

May 15, 13 7:11

Post #64 of 86 (4831 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

Hi chad,

Tripping is nice, but you have to be careful. On a cylinder, there are a lot of places you can position a trip strip that add drag, and only a very narrow range of places you can put one that decrease drag. This is also sensitive to speed and yaw, so in general tripping isn't very robust for bikes. And none of the tripped surfaces is as low drag as a good old fashioned airfoil.

In my experience, surface treatments (trip strips, dimples, rough paint, etc.) can *sometimes* reduce drag on *non-aero* shapes. But 99.99 percent of the time it's faster to just choose a good aero shape to begin with.

Cheers,

Damon Rinard, just me for now.


damon_rinard

May 15, 13 7:13

Post #65 of 86 (4828 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

Hi chad,

I keep recommending this to folks: build a fork with horizontal drop outs. Ride. Use the front skewer, choose a different rake/trail. Ride again. Compare.

Yes, some combinations ride like crap. No, most combinations aren't instant death. ;-)

Cheers,

Damon Rinard, just me for now.


chadman_98126

May 15, 13 7:34

Post #66 of 86 (4811 views)
Re: The bike that slowtwitch built [damon_rinard] [In reply to] Quote | Reply

totally agreed, not instant death, and more power to "23", and the idea of going a bit 'funny' with a 700/650 combo is a great idea for the reasons "23" cites. but as you said, I just wouldn't intentionally design something that way. :-)


chadman_98126

May 15, 13 7:39

Post #67 of 86 (4802 views)
Re: The bike that slowtwitch built [damon_rinard] [In reply to] Quote | Reply

damon_rinard wrote:
Hi chad,

Tripping is nice, but you have to be careful. On a cylinder, there are a lot of places you can position a trip strip that add drag, and only a very narrow range of places you can put one that decrease drag. This is also sensitive to speed and yaw, so in general tripping isn't very robust for bikes. And none of the tripped surfaces is as low drag as a good old fashioned airfoil.

In my experience, surface treatments (trip strips, dimples, rough paint, etc.) can *sometimes* reduce drag on *non-aero* shapes. But 99.99 percent of the time it's faster to just choose a good aero shape to begin with.

Cheers,

totally agreed, an airfoil is always better. the question becomes "what you do with the girl that brung ya?" there's definitely some good research out there on tripping cylinders and some innovative ways that I'm look at around placement and forgiveness on yaw.

best


quellish

May 15, 13 14:55

Post #68 of 86 (4527 views)
Re: The bike that slowtwitch built [damon_rinard] [In reply to] Quote | Reply

damon_rinard wrote:
Hi chadman,

In theory, covering a tri spoke with dimple film could be interesting.
In practice, it's been in the wind tunnel.
Unfortunately I'm not allowed to quote results.
But the tri spokes in our house are clean and smooth.

Cheers,


Would that be dimple film, or the 3M riblet film that's impossible to find now?


--------------------------------------------------
Yeah, it's a great bike but the engine needs work.


yakimarack

May 15, 13 18:59

Post #69 of 86 (4356 views)
Re: The bike that slowtwitch built [bujayman] [In reply to] Quote | Reply

sorry to put down all your hard work but that thing looks ugly!


MarkyV

May 15, 13 19:27

Post #70 of 86 (4656 views)
Re: The bike that slowtwitch built [desert dude] [In reply to] Quote | Reply

yer just saying that because its black!

_______________________________________________________
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23

May 15, 13 21:25

Post #71 of 86 (4607 views)
Re: The bike that slowtwitch built [cyclops] [In reply to] Quote | Reply

well, i went with the ugly aerodynamic and black stealth look. if you want to look at pretty bikes with flowers, streamers, and a cute white basket I guess you'll have to look elsewhere :)


chadman_98126

May 15, 13 22:46

Post #72 of 86 (4586 views)
Re: The bike that slowtwitch built [cyclops] [In reply to] Quote | Reply

cyclops wrote:
sorry to put down all your hard work but that thing looks ugly!

+1


chadman_98126

May 15, 13 23:41

Post #73 of 86 (4571 views)
Re: The bike that slowtwitch built [quellish] [In reply to] Quote | Reply

quellish wrote:


Would that be dimple film, or the 3M riblet film that's impossible to find now?


In my case, I recently took some old Zipp 404's and breathed some new life into them by adding some dimples and new graphics using perforated window vinyl -- this is the same perforated vinyl film that they use on store windows and buses. the vinyl used here is "50/50" -- it let's 50% of the light through. the vinyl also comes in 30/70 (i.e. lower dimple density) and 70/30 (i.e. higher dimple density). this film creates dimples about 1.6mm diameter and approx. 0.125mm deep

cost: about $32
total project time: about 45 mins
project type: total DIY hack #cheapspeed

beats having to upgrade to a new set of Zipps when the existing wheels are still perfectly good.






(This post was edited by chadman_98126 on May 16, 13 0:04)


Turd Ferguson

May 16, 13 5:08

Post #74 of 86 (4497 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

I go back and forth on liking this bike and not. I commend you for your hard work and vision to build one of the craziest looking bikes I have seen in a while.

I dig the hipster-ish hamster bars.

For the record, as I write this I am digging the bike

_________________________________________________
When all is said and done. More is usually said than done
Ba Ba Booey



bcagle25

May 16, 13 8:58

Post #75 of 86 (4369 views)
Re: The bike that slowtwitch built [23] [In reply to] Quote | Reply

holy crap dude, take better care of your lawn. But seriously awesome job on the bike!

_________________________________________________

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Chop wood. Carry water.


jjstains

May 16, 13 11:11

Post #76 of 86 (3582 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

So are those wheels actually faster now?


StephanM

May 16, 13 12:35

Post #77 of 86 (3511 views)
Re: The bike that slowtwitch built [jjstains] [In reply to] Quote | Reply

Really cool brake. Have check the HED third brake lever?

Formely stef32


chadman_98126

May 16, 13 12:56

Post #78 of 86 (3499 views)
Re: The bike that slowtwitch built [jjstains] [In reply to] Quote | Reply

jjstains wrote:
So are those wheels actually faster now?

TBD. on paper they're the same layout, configuration, sizing, etc. as the dimples now on Zipp wheels (circa 2005 and later?), but ultimately testing it is the only truth.


ZackCapets

May 16, 13 13:00

Post #79 of 86 (3497 views)
Re: The bike that slowtwitch built [jjstains] [In reply to] Quote | Reply

Interesting question. They're probably slower than they were under 5 degrees yaw, but faster than they were >5degrees yaw. You'd have to test to find out.

I did get my hands on some riblet film a while back and tried applying it to my fork, but it wouldn't stick. I'm not sure if it was too old and the adhesive lost some of its agressiveness, or if the leading edge curvature had a radius that was too small, but it peeled back at the leading edge and I ended up removing it.

Riblet film is tricky...my understanding is you have to get the riblets in exactly the right orientation or else you're literally wasting time, not to mention you'd have to match the riblet size to your flow Reynolds # and I have no idea which size riblets were on the film I had.

__________________________

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chadman_98126

May 16, 13 13:10

Post #80 of 86 (3485 views)
Re: The bike that slowtwitch built [ZackCapets] [In reply to] Quote | Reply

ZackCapets wrote:
Interesting question. They're probably slower than they were under 5 degrees yaw, but faster than they were >5 degrees yaw. You'd have to test to find out.


even at under 5 degrees they may be faster -- it depends what kind of flow separation there is and what their performance profile is - but ultimately that'll only come out with testing.

every reason to believe they're at least performant with 2005-2007 Zipps with a similar dimpled profile, but someone with better domain expertise can chime in.


(This post was edited by chadman_98126 on May 16, 13 13:10)


maverick04

May 16, 13 13:10

Post #81 of 86 (3482 views)
Re: The bike that slowtwitch built [ZackCapets] [In reply to] Quote | Reply

Hello -

I think everyone is forgetting a few things.
If the lambda is less than the 12 degrees of yaw at 40KM it doesn't matter if you are running a 650 or 700. Even though you considered the NACA 20 I think it's more important to realize that the flux capacitor needs to be running at lamda -12 degrees to hit the apex of the flying foam airfoil. If you reverse the HTA you will be better off. Makes sense, right?


ZackCapets

May 16, 13 13:59

Post #82 of 86 (3432 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

chadman_98126 wrote:
ZackCapets wrote:
Interesting question. They're probably slower than they were under 5 degrees yaw, but faster than they were >5 degrees yaw. You'd have to test to find out.


even at under 5 degrees they may be faster -- it depends what kind of flow separation there is and what their performance profile is - but ultimately that'll only come out with testing.

every reason to believe they're at least performant with 2005-2007 Zipps with a similar dimpled profile, but someone with better domain expertise can chime in.

Agreed with your first statement about testing. It's a very complex problem given that the surface in question is rotating. Some sort of circumferential riblets might be the ticket, if such a thing could be created.

As for comparability, the H3 is one of the best wheels out there at 0deg when matched with a semi-narrow tire from what I've read, but at yaw it seems deep wheels with less "spoke area" test better.

To the "flux capacitor" guy, I went to school for Aero Eng. and have been a student of the sport of tri for many moons now so I give myself free license to nerd-out on occasion.

__________________________

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chadman_98126

May 16, 13 14:11

Post #83 of 86 (3424 views)
Re: The bike that slowtwitch built [ZackCapets] [In reply to] Quote | Reply

ZackCapets wrote:


To the "flux capacitor" guy, I went to school for Aero Eng. and have been a student of the sport of tri for many moons now so I give myself free license to nerd-out on occasion.


+1 :-)

and I only play one on TV.


(did do aero though, and occasionally put it into practice: http://clarianpower.com/wind.html)


(This post was edited by chadman_98126 on May 16, 13 14:14)


maverick04

May 16, 13 14:23

Post #84 of 86 (3410 views)
Re: The bike that slowtwitch built [chadman_98126] [In reply to] Quote | Reply

Im not hating....I just wish i knew what you were talking about!


chadman_98126

May 16, 13 21:15

Post #85 of 86 (3246 views)
Re: The bike that slowtwitch built [maverick04] [In reply to] Quote | Reply

maverick04 wrote:
Im not hating....I just wish i knew what you were talking about!

that's why they invented the question mark. ;-)


MTM

May 17, 13 7:06

Post #86 of 86 (3071 views)
Re: The bike that slowtwitch built [damon_rinard] [In reply to] Quote | Reply

Kind of OT, but since the topic of cylinder aerodynamics and surface treatments was brought up...

I'm usually wearing leg warmers for my TT's (partly because I'm always cold, partly because it IS always cold were I live) and I'm wondering why no one has made any aerodynamic leg warmers. Either super-smooth and/or with some trip wires or the like. There should be some gains to be made with those two big cylinders (OK, my legs aren't that big, but still) sticking out in the more or less free air stream.

From a quick napkin calculation I get something around ~1000g of drag from the legs, så just a few percent drag reduction would be meaningful. Of course, with trip wires (which I knew Smart Aero Technology looked into on their long socks) it could be tricky with the leg angle changing both between riders and within a pedal circle.

Also, I guess the pro's would never wear them because the cycling culture forbids you to ever wear anything but bare legs in a race, but for those of us who doesn't care so much about the culture and more about speed it would be nice.

 
 
 
 



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