Designing a New Uni Frame

you have not seen the triton frames with a seatclamp welded to the frame?

I’m not a mechanical engineer, but I like to pretend…

  • I would wager that the amount of force required to shear that pin would be less than the force to break the typical bolt configuration we normally see.
  • How does the pin stay in?
  • If there is any play in that hinge side, I would think the movement will wear the parts. Can that hinge be manufactured to avoid play and still allow it to hinge when needed?

It’s true that having a separate seatpost clamp gives you options, and that can’t be denied.

Stripping the threads is really not a problem if the attached fitting is designed in the traditional way to accept a seatpost binder bolt. This kind of bolt has a sort of tee nut that fits from one side, and a normal recessed allen bolt from the other. If it ever gets stripped you can easily replace it. When exotic frame materials like carbon fiber started to hit the scene it seatpost clamps were used as it was the easiest way to get a seatpost tight without sacrificing the integrity of the frame. At first it looked sloppy, and clumsy by comparison; however, it quickly became associated with high end frames and was adopted for frames that didn’t require it to make them seem more high end.

You may be right about the pin strength compared to the bolt strength, but I think either would be more than strong enough for the purpose. The problem I see with it is the relatively small amount of material holding the pin. There is a high potential for the aluminum to crack at the center of the joint where there is little material supporting the pin. I think this is why the current attempts at QR bearing holders have been chunky looking, or made of steel. The basic design has been done before, so what about designing something less obvious. I have a vision of a band style clamp that would replace the lower bearing holder on a frame. I think it could be done to be plenty strong for a freestyle/road uni, and with some testing and development it may be suitable for MUni/trials.

Thanks everybody for the feedback, this is why I posted my concept so people could contemplate what is good and what is not. all of your ideas are very helpful and i will keep you updated with my progress

That’s funny ive had this carbon frame for a year and a half http://www.mikepadial.com/myunicycle.htm abused it so much and its fine,lightest frame on the market

I wish my uni had a way to lock it…you can run a cable through the seat and wheel/spokes but there is no way to secure the frame. It is one reason I like the looks of the Nimbus frame. I’d like to have a uni frame that I could lock up while I do other things downtown. I realize a determined thief can and will get something they really want–my desire is to frustrate the impulse ideas of the curious.

Carey

We need to be able to grind on our seattubes! haha

Bike lock ring would be good.

You can secure your frame without one, but it takes a lot more work, and knowledge of knots.

I just use a coiled bike lock and run it behind the frame, through the spokes, and then around the rack or whatever object I am using. It keeps the frame from falling because the extra length just coils back up and supports the weight of the frame. By using a seat clamp that requires allen keys instead of a quick release i imagine the post and seat would be less likely to be stolen.

I mention this because all it would take to steal the frame is to remove the bearing caps.

I mention this because all it would take to steal the frame is to remove the bearing caps.

Fixed

Enough for the casual theif, but Carey is right in that all it would take is some allen wrenches.

There are a few knots that you could do with a cable that isn’t too stiff around the fork, just above the tire, but it also requires that you use up all the cable and have it be tight when you finally lock it.

I will throw a few things in for you to think about:

Bearings can be distorted easily by the force applied to the outer casing, so you will need a low (but secure) clamping force - this is more so with ISIS bearings with their thinner outer casings…

Have you though about not using pins? use the material itself as a hinge, you could make a really nice organic shape with the upper and lower pieces working together.

What about using a spring clip of some kind to lock two pieces together? Steel has it’s uses you know. :wink:

Why have the extra material on one side of the bearing houseing… extra weight? :stuck_out_tongue:

The clamping of the bearing should be done on the centre line of the bearing or the loads would distort the bearing and stop it running (you may have it in the centre but it is hard to tell from your model).

If cost is no issue… then consider that the two pieces could close shut and this will give you considerably greater design options… if you need to consider cost… then you need to realise that this is probably not possible and work out how to deal with the tolerances.

You also need to think about the forces on the bearings/bearing holders. As the frame flexes (yes all frames will flex) their will be an outwards force on the bearings. When you jump there is a compressing force on the bearing and their holders. You also need to consider that as you ride there is vibration on the bearings and frame.

Hope this helps.

Roger

here’s a quick update to my progress.

as part of the assignment I must have a client to work for. so I’ve been talking to Tony from UDC NZ about designing this frame for nimbus (not that they are actually going to make it or anything but to create a list of certain requirements for me to follow during the design process).

since the last set of screen shots, i have made the hinge a bit better by enlarging the pin hole and developed the cut away sections for the corresponding hinge lug to slide past as the hinge is opened. I have created looking bolt end and made a recess for the bolt. Also I have put the Nimbus log on (I know that this is not the perfect font but its the closest I could find). underneath this I will have a thin layer of carbon fibre to strengthen it but also tie in together to the rest of the frame.

The last pictures are of the development of the legs. it is built like a knife handle - two carbon fibre tubes are sanwedgeing a tin slice of aluminium which will be drilled to save weight. this construction will be super strong appealing and light weight.

Our school is looking at getting a 3D printer whiten the next few months. so I might be able to print the completed design and model it which could be cool.

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Looks realy cool! Looking forward to seeing it finished!

done the crown now, below are some pics. enjoy.

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That is one of the prettiest looking crown patterns I have seen yet. I was going to mention that those points on the crown/leg connection are going to be pretty severe stress risers but read back a bit and found you are planning to basically use a double leg glued together right? It should be OK then since the stress would be focused on the inner double wall part.

That is pretty cool but can you get carbon tubes in that shape?

Looks awesome!

Thank you, I was really trying to make something that had clean lines, was interesting with a few curves and angles but was ales strong in structure and design. I’ve done a bit of research into carbon fibre and it isn’t actually all that hard to create tubes in any shape or size. The modern way to do it is to have a foam moulded mould with the carbon fibre sleeve (woven into a circular orientation with no joining seam) tightly applied around the foam. The tube is vacuumed in a plastic bag with the resin to join it all up to the foam with an even amount of resin all round, the tube is then put in an oven heated to around 200 C to cure. Doing it this way creates a strong tube that the foam can be dug out or kept in and bonded to the rest of the frame.

I had a carbon bike frame with that style of tubes.