pic: Simple Chain-in-Tube Concept
 

Re: pic: Simple Chain-in-Tube Concept
 

I really like the use of tubing to mount the ballshifter, very clever.

Re: pic: Simple Chain-in-Tube Concept
 

Thanks. I basically got rid of the plate and standoffs that come with the 3rd stage kit and made the output shaft and gear part of the drive rail. The gearbox then bolts on. I had reservations about putting 3 bearings on the same shaft, but since it's bolt tolerances holding the 3rd one on, I'm fairly comfortable with it.

Here's a pic with one gearbox removed.

Re: pic: Simple Chain-in-Tube Concept
 

Brilliant. This is the current weakness in our chain in tube design using the ball shifters. Consider this stolen :cough: I mean borrowed.

Re: pic: Simple Chain-in-Tube Concept
 

Send me a PM if you'd like the CAD model.

EDIT: Link below.

Re: pic: Simple Chain-in-Tube Concept
 

Very nice Ty!

Re: pic: Simple Chain-in-Tube Concept
 

You mention reducing the diameter of the outer wheels, have you considered increasing the diameter of the middle wheel?

I'm thinking that versawheels with blue nitrile might have a large enough OD to give a decent amount of rock with 4" Colson wheels on the outside.

Alternatively, you could use 4" wheels on the back and middle and a 3.5" wheel on the front. That gives you the same amount of rock as a 1/8" center drop.

Edit: You can also use a vex 16 tooth sprocket on the 3.5" wheel down from the 17 tooth sprocket on the 4" wheels to try to get the surface speeds of the wheels more closely matched. This should reduce wheel wear.

Re: pic: Simple Chain-in-Tube Concept
 

There's definitely a lot you can do with the wheels, I'm just a huge fan of the durability of Colson wheels and we have a lathe handy right in our workshop.

I've had a few extra requests for the CAD model, so here it is.

Re: pic: Simple Chain-in-Tube Concept
 

Thanks for the CAD, looks pretty darn simple and bulletproof.

As far as colsons, Vexpro has 4", 3.5", and 3" Colsons. If we build something like your design I think we will use 1/2" smaller dia front wheels, whether we use 4" or 3.5" wheels for the rest.

Re: pic: Simple Chain-in-Tube Concept
 

How are you going to attach the two vertical pieces of tubing to the horizontal frame tube on each side? It looks like there is not a lot of surface area and any fasteners that protrude into the frame tube may interfere with the chain and/or sprocket.

Re: pic: Simple Chain-in-Tube Concept
 

What's the reason for the slots in the tube that mount the gearbox?

Re: pic: Simple Chain-in-Tube Concept
 

Probably to not overconstrain things.

Re: pic: Simple Chain-in-Tube Concept
 

You want the gearbox position to be driven by the third bearing in the plastic housing piloting onto the shaft captured in the tube. This sets the appropriate gear spacing and prevents misalignment of any the bearings or the shaft. Then the bolts just clamp everything in place wherever it ended up.

I also really like the boxtube standoffs. I'd played around with this same idea, but still using a version of Vex's third stage plate, requiring more pieces and more disassembly to get the gearbox away from the final gear. The boxtube cleans this up a lot.

Re: pic: Simple Chain-in-Tube Concept
 

Really nice job Ty....thank you for posting your model. I think this design concept will start to become more popular in the near future.

Re: pic: Simple Chain-in-Tube Concept
 

We have a TIG welder in our shop, so they'll be welded in place. If you don't have access to a welder, basically any motorcycle shop near you will have one and you could work with them for a sponsorship.

Mostly to not over constrain things as stated above. Secondarily to make it so that I don't have to keep track of left and right versions of the tubes since putting a hole in the middle of the tube would cause the tube to interfere with the gear on the rail.