C3 Rag Joint Restoration

[Tom K.]

Re: C3 Rag Joint Restoration

Hi joe,

I understand completely. I would not want a 'home made' steering part either. So, I plan to do a better job than that.

If the part ends up similar in hardness and flexibility to an original part (I have seen some up close and have some idea what it should be like), the next thing to do will be some testing. There doesn't appear to be anything special about the rubber and cloth materials, I think the magic will be in the adhesive. I am using the fixture to apply a clamp load and the parts and fixture will be heated to help curing. If the first adhesive doesnt work, there are many others. I'm pretty confident that I can get something at least as good as one cut from the sidewall of an old tire which is what most rebuild kits are made from. Either way, I only plan on making one for myself and sharing what happens with the group. If I screw it up, the next person may do a better job because they will know what doesnt work.
Again, does anyone have any input on how to test these things, other than installing it in my car and driving?


Tom Krause

[Ed S.]

Re: C3 Rag Joint Restoration

Your comment: "There doesn't appear to be anything special about the rubber and cloth materials....." I think you are under-thinking this. I suspect when the part was originally designed the physical characteristics and properties, and performance parameters, especially under twisting load tests were critical to their selection and design, i.e., the number of layers. Adhesive is critical too - and in that regard time and science is on your side - the chemical industry had developed adhesives since those original rag joints were manufactured that are extremely strong. But if you use the strongest adhesive available to bond inferior components together that cannot withstand stress you have a piece of junk. Unless you can find the performance specs of the rubber and fabric material they used back in the day you are wasting your time.

[Tom K.]

Re: C3 Rag Joint Restoration

Hello Ed,

The materials available at the time these items were originally designed were almost certainly neoprene rubber and cotton duck canvas. I suspect the same is true of the adhesive. The capacity of the part under a twisting and reversing load should be easy to test. I am thinking of using a couple of scrapped shafts, cutting the splines off, and welding them to a simple shaft turned by a motor and guided by some hardware store pillow blocks. Again, mostly cheap stuff that will cost me some time, but not a lot of $$. The shafts would join up to a steering coupler and flex the disc the same as in a vehicle. Then there is the question of how much torque load is there in actual use, and how to simulate it....
None of this stuff is that hard to do, I just enjoy tinkering with stuff like this. I think a test like this will show pretty quickly if the part is capable or not.
Any other ideas out there??


Tom

[Tom K.]

Re: C3 Rag Joint Restoration

Hello All,

Here is where I'm at now, as usual, I could not put much effort into this so it took longer than I thought to get here. The pictures show what I end up with after cutting the od and putting in the holes. The process seems to work to make a part that has the right size and shape. Now I need to get the adhesive sorted out. The pix with the yellowish looking cloth were done with contact cement (which soaks right into the cloth and colors it yellow) and they adhere together but I doubt there is much strength in the bonds. The flexibility of the disc feels about right, but may need to be slightly more rigid. The thickness of the stack is almost exactly what the layers of rubber and cloth add up to (about 0.377") The contact cement did not seem to add any measurable thickness.

The other two discs are made using a black polyurethane adhesive that didnt seem to soak into the cloth very much so the cloth looks white from the side. These two discs are way too rigid for the application, and they dont seem to adhere as well as the contact cement. Thes discs seem to add about 0.025" to the thickness of the finished parts as compared to the contact cement. Maybe this indicates the glue started to dry a bit before clamping and thats why it isnt a strong bond?

I have some more adhesives to try, so I guess that is my next step.

Does anyone have any ideas on adhesives or rubber materials or cloth materials or testing? Beyond the functional test with some hardware store bearings and a wooden frame I sketched out above I havent come up with anything better. Anyway, here are the pix of my latest attempts.


Tom

[Tom K.]

Re: C3 Rag Joint Restoration

Hello All,

It has taken awhile to get something that is ready for testing, but the two parts in the pictures below are my first pieces good enough for testing. The size and shape seem good, and the layers hold together, but Im still not real confident in the strength of the adhesive bonds. The thickness came out about 0.41" but it seems somewhat too flexible to me. I have a different type of adhesive to try that claims to be the greatest thing since sliced bread, but time will tell. Anyway, here are the pix of what I have so far.
Any ideas for testing other than what I mentioned above?

Thanks in advance for any advice


Tom