Re: Team 971's CAD Archive Release
 

How did you guys figure out all the center to center spacing on your belt reductions in your top jaw?

https://scontent-b-lga.xx.fbcdn.net/...c9&oe=545E6457

Re: Team 971's CAD Archive Release
 

It's not center-center spacing. From what I can see, there's a Cam (which looks like a bearing attached with a hex nut) used to adjust the tension of the belt.

Re: Team 971's CAD Archive Release
 

It's not actually a cam, it's just a bolt in a slot which we push on until it is tensioned and then tighten down.

Re: Team 971's CAD Archive Release
 

Alex,

I uploaded a thread in the CD media that shows the sketch we used for our shooter gearbox (it is the same principle, just a cleaner example of it). The picture is accompanied with a description. Please let us know if you have any further questions about this.

http://www.chiefdelphi.com/media/photos/40812?

Also, for note, we are not entirely pleased with our tensioner slot method. We have found that once you tighten down the bolt, even with a fat washer, the material gets swagged into the slot, and the blot doesn't slide freely the next time. This could be improved with more clearance (in hind sight the .252 clearance was un-necessarily close) coupled with possibly a different clamping method. We will see what we decide to do next season.

Re: Team 971's CAD Archive Release
 

So I was looking at your gearbox and I'm a little confused as to how the CIM motor shaft extension is held on. Is is press fit onto the CIM motor or is keyed?

Re: Team 971's CAD Archive Release
 

Press fit. We did all the math to make sure it won't slip.

Re: Team 971's CAD Archive Release
 

Starting in 2011 or so, we'd ream .001 under and just hoped it would work!

We tested torque required to slip and found it exceeded what we need by a good margin. I mean we used a 3-4 ft lever arm w/ some weights.

Re: Team 971's CAD Archive Release
 

Awesome, thanks for the data point! I believe we used a 0.0015 press, which just worked for similar reasons. That was some fun math to do. You can treat the hex like a pressure chamber, and figure out the force required to slip it. I remember calculating that we needed 300 lbs of force to press it on.

This year, we left a step at the end of the bore so we could press it on until it hit the end of the CIM shaft. That worked well. You can see it in the model.

Re: Team 971's CAD Archive Release
 

You could also leave a small pilot hole on the end to insert a pin gauge to determine the press depth and to relieve the pressure while pressing on the adapter.