pic: Simple Chain-in-Tube Concept

[Bennett548]

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.

[philso]

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.

[Gregor]

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

[AdamHeard]

Originally Posted by Gregor

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

Probably to not overconstrain things.

[Aren Siekmeier]

Originally Posted by Gregor

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

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.

[TD78]

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.

[Ty Tremblay]

Originally Posted by philso

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.

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.

Originally Posted by Gregor

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

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.

[pribusin]

Nice! Do you have a cutaway of the inside of the tube-in-chain? I'm not quite sure what the inside would look like. How do you assemble this? are there access slots/holes to access the chain?

[billbo911]

I really like this design and may consider proposing it, if it makes sence for the game.
I do think there is a problem with it though. Assembling the transmissions to the chassis. (Please correct me if I wrong here.)

If I am seeing this correctly, the tube mounts need to be installed to the frame first, then the transmissions to the mounts. The problem is, the drive shaft is long enough that motors will not allow correct alignment to the two rail bearings because the belly pan is in the way. Servicing this, or replacing a motor might be a bit difficult.

If these issues are easy to address, please explain how. I like this design and would love to use it!

[Aren Siekmeier]

Originally Posted by billbo911

I really like this design and may consider proposing it, if it makes sence for the game.
I do think there is a problem with it though. Assembling the transmissions to the chassis. (Please correct me if I wrong here.)

If I am seeing this correctly, the tube mounts need to be installed to the frame first, then the transmissions to the mounts. The problem is, the drive shaft is long enough that motors will not allow correct alignment to the two rail bearings because the belly pan is in the way. Servicing this, or replacing a motor might be a bit difficult.

If these issues are easy to address, please explain how. I like this design and would love to use it!

The drive shaft on the middle wheel, along with the gear on that shaft, remains in the tube when the transmission is removed. The interface between the removable transmission and the frame consists of the mounting bolts and the gear interface.

[billbo911]

Originally Posted by Aren Siekmeier

The drive shaft on the middle wheel, along with the gear on that shaft, remains in the tube when the transmission is removed. The interface between the removable transmission and the frame consists of the mounting bolts and the gear interface.

Right, forgot about the third stage! That make perfect sense. OK, supper easy assembly and repair them, got it.

[waialua359]

I cant believe I missed this thread earlier. We may look into this.
Even with the relatively small amount of space saved, makes a big difference on the footprint of the control system parts on the bellypan.
With a modulated frame that we are using, this is even easier to access our chain.

[Ty Tremblay]

Realized I've been having a 7 month long brain fart.

If you increase the spacing of the output gear from the rail by .25", you can bolt on 1"x1"x.125" tubing and use that to mount your gearbox. VexPro sells .25" acetal spacers with a .5" hex broach.

Top-down view

[RyanCahoon]

Originally Posted by Ty Tremblay

you can bolt on 1"x1"x.125" tubing

Top-down view

How difficult will it be to install those gearbox mount bolts?

[Ty Tremblay]

Originally Posted by RyanCahoon

How difficult will it be to install those gearbox mount bolts?

The bolts holding the gearbox to the 1x1 tubing? Very easy.

If you're talking about the bolts/screws used to attach the tubing to the drive rail, it's just a matter of lining up the holes and getting a bit started on the other side. I'd suggest doing it before installing any wheels, bearings, or chain.

I'm about to hop on a plane, I'll get a couple more screen shots and the updated CAD as soon as I can.