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Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT
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I am currently working on a small project on my 3T VOLA aero-bar to get a BTA aero-bottle bridge replacement to the stock bridge provided by 3T.

I have always wanted to install an aero bottle (like the profile design HC bottle) or at least a standard bottle cage with a standard bottle in between the arms.
There is always the solution to install some brackets between the extension but with the 3T VOLA aero bar, I have always found that the bottle was too much Forward and that the structural link between the block/raisers ( which I call the bridge) was taking useful space.

Note that 3T does not allow to modify their products and doing so would void any warranty.

Here are the few steps for my project:

1. Design a bridge that would re-use existing provisions on the 3T VOLA aero-bar.

I came up with few different designs allowing to have the bottle cage installed on the bridge at few different locations (forward & aft).
The bridge holes are exactly at the same locations than the 3T bridge.
I have done few designs where the bottle z-location (height) could vary (see pictures) but for aerodynamic & cost purposes I will keep the bottle at the same height as the arm. (i.e. the final bridge most likely going to be a plate: V1 on the picture below).


2. Prototyping check

I have used a 3D printer to prototype the V2 model (see picture). The 3D printed part is a plastic part ( ABS plastic) which is not structural. Tensile strength is around 31MPa, structural Aluminum like 2024 T3 have tensile strength in the range of 400MPa and carbon UD in the range of 600MPa in the fiber direction.

I have then installed the prototype on the bike to verify fit and function. As you can see on the picture the fit is perfect.
I have had no time to model in 3D the rest of the bar and the bottle/bottle cage but I am going to do so in the coming weeks.

3. Short term solution

In the short term solution, I am going to use both the 3D printed bracket and the 3T bridge. I will installed the 3T bridge upside down. I just want to make sure the stock screws have enough thread engagement after stacking up the two bridge. If not I will get new screws. A good rule is to make sure you have at least 2D of thread engagement.

4. Long term solution

For the long term solution, I will be working to make the bridge structural, likely by using 2024 T3. The thickness of the plate will be chosen so that it can withstand pre-determined loads. I am currently in the process of defining the load cases. I will also most likely model the 3T bridge and do a side by side comparison of inertia/stiffness and strength (all that using finite element analysis). My bridge is inherently larger than the 3T bridge but at the moment I don’t think I want to have it with the raise portion (as the 3T one).

At the moment I am thinking the that the bridge is mainly taking load in its plane and that compression failure or buckling are to be checked.
To give you an order of magnitude using the design V4 a compression load of 100N in the direction of the bridge, it would take a load 58 times greater to get the first buckling mode. Meaning 100N x 58 =5800N = 591 Kg. I do not think anybody can put such load into the bridge. Stress in the bracket are not an issue with the 100N.

I am thinking that the shape of the 3T bridge is going to be more compliant than my bridge. I think the 3T bridge does have some built in in-plane springiness which probably enhance helps damping out some vibration.

Finally, I will need to ride the bike to make sure there is no rattling or odd vibration. If there is I might have to center the bottle more on the bridge or design slightly different platform.

I would be glad to hear what comments you have on this small project.
Last edited by: etienne: Dec 21, 17 15:08
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [etienne] [ In reply to ]
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Last edited by: etienne: Dec 21, 17 15:10
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [etienne] [ In reply to ]
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Good job! You basically did what 3T should have done right from the start.
I hope they will include a bta solution like this when they'll design new bars (I'm pretty sure I'm not the only one waiting for that).
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [etienne] [ In reply to ]
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I'd considered doing something like this for my customers (I did it for felt Bayonet 1 bar)
I would put in extra pad mounting holes too as the options on the bar are pretty limited - a well designed bridge could significantly improve the bar
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [etienne] [ In reply to ]
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NICE! When will you be marketing them? :D
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [etienne] [ In reply to ]
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I have a Vola Team Stealth bar, not using the supplied bridge because I’m not towering my cradles. Your design is nice, 3T does have a bridge BTA just so you know.
https://store.3tcycling.com/...team-bridge-510.html

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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [etienne] [ In reply to ]
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I guess I did not realize that 3T sells one. I contacted 3T to get some info the other day and they did not mention it :)

I am still going to finish mine. It should give me more adjustability and holes for a garmin mount bracket.
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [etienne] [ In reply to ]
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They also have this...and has a Garmin Mount.

https://www.3tcycling.com/...ed-hydration-system/

Yours looks killer, well done, are you thinking of selling any when completed?
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [Pwraddr] [ In reply to ]
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Nice job on your 3D print design.

I have the Ventus aerobars, and I have always been toying with (fabricating) a BTA mount. I made one years back that was tig welded to the arm rests clamps. I have now since made another that is cut into the stack spacers. I will take some pics and post them shortly.

Team Zoot-Texas, and Pickle Juice
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [Taugen] [ In reply to ]
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Here is a picture showing what I did. I had to mill a slot in the left/right stack 60mm spacers that the extension clamps sit on top of. I milled the 60mm stack spacers down to 40mm based on my total stack height I needed. I milled the horizontal slots into the spacers so that I could then use a piece of Kydex cut to fit the slots and fit the width as the bridge to which I will then drill 2 holes for a BTA bottle cage. The Kydex bridge also serves as a tensioned spacer between the stack spacers and shoulders up against the 2 vertical mounting long screws, so that the extensions and spacers all stay tensioned in place and can't splay outward or pull inward.

Team Zoot-Texas, and Pickle Juice
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [etienne] [ In reply to ]
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Good job! What about building some more and selling them on ebay?

Stay home, stay healthy.
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [etienne] [ In reply to ]
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Small update on the project. I have got the final product laser cut from aerospace grade Aluminum 2024 T3, 3mm thickness.
The part looks great, I need to go ahead a weigh it. But before the next step is to finish up sanding and spray paint it black.
Last edited by: etienne: Jan 20, 18 9:15
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [etienne] [ In reply to ]
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First off awesome design! What FEA software are you using? Also completely agree on the thread engagement 2x dia especially into aluminum. Probably the most frustrating thing on bikes these days is how joint design is overlooked.
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [kart17] [ In reply to ]
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Thanks !


For the FE models I used the solver built in CATIA V5, called ELFINI.
It is a linear solver and there is the possibility to compute the buckling modes for the structure. It is very easy to use when the part is design with CATIA, you can have the FE model in a matter of seconds...

The two front holes can be used to attached the bottle cage more forward but in my case I will use them for a computer mount (like garmin) that I will design and 3D print. I want to be able to have the computer visible when I am on the aero bars.
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [etienne] [ In reply to ]
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Minor update, the bracket is sanded, painted and ready to be installed !


Last edited by: etienne: Mar 24, 18 18:44
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [etienne] [ In reply to ]
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I did a similar thing
it went through a few iterations, eventually to the point that I mount a very small simple bracket to the stem cap now instead


https://www.thetrinerd.co.uk/...he-bars-bottle-mount



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http://www.thetrinerd.com
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Re: Cervelo P3 - 3T HANDLE BAR BTA BRACKET DESIGN PROJECT [etienne] [ In reply to ]
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I don't mean to sound skeptical, because I love your design, but why not simply use cable ties?
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