pic: GEAR & CHAIN IN TUBE 8WD

[nuclearnerd]

Originally Posted by pwnageNick

I utilized a US Digital S4T encoder, which did require a coupler and custom mount plate, but you could easily use one of the CIM encoders VEX sells instead for simplicity.

Or you could use a hex bore encoder

[pwnageNick]

Sorry, couldn't get to my computer until tonight.

Originally Posted by Cothron Theiss

Any chance we could get some more detailed renders of the gearbox/chain runs? What I can see looks great, but it's hard to ascertain the specifics from this.

Here you go (sorry for the large image file)

Originally Posted by InFlight

I understand the attraction of belt/chain in tube drivetrains as a design exercise.

The trade made is very involved and long replacement times if a belt/chain/axle/bearing failed during a competition. You could very easily miss a match for the amount of time it would take to replace any part.

Considering maintenance, and tensioning should be prime considerations in determining the best way to implement a belt/chain drive train.

Originally Posted by Cothron Theiss

I would try and tweak the design so that the ends of the drive rails are open, so that if you do need to get to your chain or gears, you don't have to disassemble your chassis frame.

Well in this specific situation the top half of the chain runs inside the tube while the bottom half of the chain runs under the tube. So using masterlinks the chain would be easily accessible and easy to switch. Maneuvering around the sprockets should be fine with the access slots on the bottom of the tube.

I do agree that this chain setup is not ideal, but I kind of got worked into a corner with trying to fit everything in the tube.

I am working on a variation right now with smaller wheels, and a 2" height tube, and am attempting to have the entire chain run inside the tube. The challenge there is you have to choose between:

(1) Motor clump on the corner wheels which for everything to fit means that your wheel is pushed further in from the front/back of the chassis so the CIM can sit in front
(2) Motor clump in the middle and your tube gets wider to accommodate both sprockets on the wheel shaft and the gear.

I keep going back and forth on which I'd prefer. May end up designing both and seeing how they both look as an end result.

[Cothron Theiss]

Originally Posted by pwnageNick

Well in this specific situation the top half of the chain runs inside the tube while the bottom half of the chain runs under the tube.

Ohh, I had not noticed that. That's a very interesting concept; I'd like to see somebody try that out.

So using masterlinks...

Master links with what looks to be #25 chain? That's living dangerously.

I am working on a variation right now with smaller wheels, and a 2" height tube, and am attempting to have the entire chain run inside the tube. The challenge there is you have to choose between:

(1) Motor clump on the corner wheels which for everything to fit means that your wheel is pushed further in from the front/back of the chassis so the CIM can sit in front
(2) Motor clump in the middle and your tube gets wider to accommodate both sprockets on the wheel shaft and the gear.

I keep going back and forth on which I'd prefer. May end up designing both and seeing how they both look as an end result.

Your gearbox and sprocket integration is quite nice, and it would be very impressive to see a design with all the power transmission components enclosed in 2x1" or 2x1.5" tubing. Can't say for sure, but I imagine for your purposes, tweaking your gearbox to make option (1) work would be pretty simple. You might even be able to just rotate the two motors forward around the driven gear and keep those corner wheels out near the edge of the frame.

[pwnageNick]

Here is the updated version I ended up with.

-23.33lbs, only parts missing are chain runs, and bumper supports I suppose (all hardware besides rivets included)
-24"x32" chassis
-4"x1.5" VEX Colson wheels (1/2 hex bore)
-11:70T Single Stage reduction within the drive tube
-Drive tubes are 2x2x.125" 6061, while the front and back tubes are 2x1 Versa
-All sprockets are 16T #25 VEX sprockets with the chain run fully contained inside the tube
-The middle wheel is dropped 1/16"
-In this current configuration a US Digital S4T encoder is utilized, though the CIM encoders could easily be used instead, or a Grayhill, etc.
-All parts are COTS except for the two drive rails, the two encoder plates, and the belly pan (could be lexan, wood, etc. for low cost)
-The only other modified parts are the front and back rails (lightening pattern), shafts cut to length, and the direct drive shaft is turned down on one end to 3/8" round to couple to the s4T encoder (optional depending on encoder use)

Apologies again for the large picture:

[asid61]

After initially dismissing the idea as "sketchy" because of the integrated gearbox, after looking at the lower custom part count and the resulting reduction in cost, I think this is a great idea for making a custom chassis at a low cost and weight.
I don't like your lightening patterns, but apart from that the design looks great. The dual versagussets in the corners really stand out to me as a feature of 2x2 tubes.
Do you think it's possible to make a shifting version? Can all the gears + sprockets fit?

[Travis Schuh]

Originally Posted by pwnageNick

Well in this specific situation the top half of the chain runs inside the tube while the bottom half of the chain runs under the tube. So using masterlinks the chain would be easily accessible and easy to switch. Maneuvering around the sprockets should be fine with the access slots on the bottom of the tube.

Have you run a chain below tube/drive chassis/bellypan like this before? Do you run into issues with getting carpet junk into the chain or having the chain exposed to accidentally being hit on things? I am curious because we are considering running a similar chain setup, but don't have much relevant experience to base off of.