Building a Cam

looking good kevin.
any plans to put some texture or ribbing on the lobes?

way cool. been fun following this project.

UPDATE:

Yesterday I added lightening holes and trigger wire holes to the lobes. Geting really close and all the machining that's left to do is to machine a trigger bar. I was originally going to go with a round bar, but attempting to drill small holes in it has broken several bits, so I am going to machine a small flat rectangular bar instead. Will also cut teeth into the lobes on Monday. Ian Stewart- I wish I didn't have to machine so much off, seems like a waste to me, but the plate I ordered was the thickness of the stem, which is what I needed.

All of the lobes ready for teeth

Up close detail of machining done to lobes.

UPDATE:

Got the teeth cut into the lobes today and started assembling the cam. Got the upper part of the trigger wires attached and a trigger bar machined. Unfortunantly, the trigger bar was a bit small, so tomorrow I will machine a new one and hopefully finish the cam.

Almost there...

I know the lobes are a bit tweaked, but once I add another washer to each side they should be fine.

Looking good! I know this is your baby, but are you going to test it when complete?

looking good amigo

Project looks great. Thanks for cotinuing to share your work.

nice project Kevin keep the pics coming! My first set of nuts was homemade.i rounded up all sorts of scrap metal pieces i could find around the shop and drilled & swagged them. Heavy but bomber.

UPDATE:

Finally finished the cam today after running into really the only roadblock of building it... the trigger bar. between snapping bits and bending bars I had really bad luck making something work. Yesterday though I got it all worked out and machined a flat rectangular bar. Today I added trigger wires and since I don't have access to a swaging machine, I just threaded both ends of the wires through a small piece of copper tubing and then hammered it flat until it was tight. Probably a temporary solution and I can't actually retract the cam yet. This weekend I plan on sewing a sling onto it using heavy duty nylon thread. Thanks everyone for the support and advice, this has been a really fun project and when I get specs for weight and range I'll post them up.

Side View

The cam

My cam next to a BD C4 #2

Close up of my improvised swage job

All the trigger bars I went through...

Hey Kevin,

The cam looks great! Nice machining! Btw, I am curious how the springs are mounted on the side lobes. I don't see how they are connected to the lobes from the pictures on page 2.

:)

Looks clean, and executed well. Don't forget to deburr and break sharp edges. You could also round off the end of the stem with a radius.

Awesome work and cool project! Thanks for keeping the thread updated so we could follow along. Keep it going and do some light load testing when you're ready!

Colin Parker wrote:Awesome work and cool project! Thanks for keeping the thread updated so we could follow along. Keep it going and do some light load testing when you're ready!

I disagree with Colin, destructive testing would be a great idea. Do you have access to a load cell at your school in your materials engineering lab?

A destructive test will also show you your failure points. Hardest part is picking the best test (i.e. what failure mode to test) and the best way to record and quantify your results.

I think starting with a dynamic factor two fall would good. You can check for deformation and then keep preogressing the tests until something busts or bends beyond usability.

If you do dynamic testing be sure to wear safety glasses and stand back. I helped my son with a middle school science fair project where we looked at the peak loads of different anchor setups at failure. When things broke the recoil was impressive and I sent stuff flying all over our garage.