pic: Team 3647 West Coast Drive

[Mk.32]

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[Chris is me]

Great job!

I bet the gussets could be 1/8" thick instead of 1/4" and still hold up.

I would add some kind of cross bracing connecting the two gearboxes together. This will make your whole frame more rigid and provide those gearboxes and CIMs with much needed support.

[JesseK]

Ditto Chris for the transmission support. 1/8" plate, bent at the proper angles and bolted to the front of the transmission and joining at the top of the side rails may solve it.

[JamesCH95]

Looks like a good start!

I would seriously consider riveting a belly pan made of thin sheet (0.030" aluminum or 0.040" polycarbonate maybe) to the entire bottom of the frame and omitting the bottom gussets. This will be a nice place to mount electronics and other components as well as stiffening and strengthening the frame substantially. Ditto on making the gussets thinner also.

[Mk.32]

Thanks for the feedback!

Slight updated version, bigger standoffs and nutted/bolted.



The gussets currently are 3/16, so 1/8th would hold up just as well?
And replacing the bottom gussets with a poly carb bell pan sounds like a good idea.
I am thinking of using this: http://www.andymark.com/product-p/am-0836.htm

Also I am debating between using eClips or threaded ends on the shafts to hold the wheels in place, would you would guys recommend?

[Thad House]

One idea I would have would be to move the center sprockets to inside the transmission plates. This way the outer transmission plate could be touching the chassis which would give much more support to the gearboxes.

[Mk.32]

Originally Posted by sst.thad

One idea I would have would be to move the center sprockets to inside the transmission plates. This way the outer transmission plate could be touching the chassis which would give much more support to the gearboxes.

This was something I thought about but the reason why I didn't do it was because the gearboxes are fully based on the toughboxes. If I changed the layout of the gearbox (moving the sprockets inside), it would mean we would need to make custom shafts and I want to keep machining down as much as possible.

[Thad House]

Originally Posted by Mk.32

This was something I thought about but the reason why I didn't do it was because the gearboxes are fully based on the toughboxes. If I changed the layout of the gearbox (moving the sprockets inside), it would mean we would need to make custom shafts and I want to keep machining down as much as possible.

We were able to do this without making custom shafts by using the cluster shaft from a supershifter. the main output shaft works with a larger gap without any issues as long as you get the extended output shaft

[Mk.32]

Oh I will definitely look into that, thanks!

[JamesCH95]

I notice that you have some rather serious looking fasteners going all the way though the transmission and frame tube. I would suggest making those fasteners smaller. Graded 1/4-20 bolts will be plenty strong enough, even graded 10-24 fasteners would work fine.

I would also suggest having either an insert in the frame tube to transmit clamping loads from the bolt, or have a clearance hole on the outside tube wall and have the bolt only clamp to the inside tube wall. Otherwise it becomes easy to bend or crush the tube with zealous tightening.

[Mk.32]

They are 1/2-13, I wasn't sure how well 1/4-20s would hold so I went big... but I guess it wasn't needed.
I will make the outsides holes, clearance holes in the next revision for sure.

[JamesCH95]

Originally Posted by Mk.32

They are 1/2-13, I wasn't sure how well 1/4-20s would hold so I went big... but I guess it wasn't needed.
I will make the outsides holes, clearance holes in the next revision for sure.

Sounds good. A 1/2-13 bolt is serious overkill. It's proof load would be 7,800-17,000lbf depending on grade. (I know this is a somewhat arbitrary value, I intend it as an 'order of magnitude' indication of it's strength, i.e. you could comfortably hang an F350 Super Duty truck using one of these bolts).

Here is a nice chart for bolt strengths: http://www.almabolt.com/pages/catalo...oadtensile.htm

A common rule of thumb is designing to 75% of proof load.

[Mk.32]

After taking all the feed back, here is another go:



Gearboxes are now mounted right on the frame with AM SS shafts.
Poly Carb belly pan replaces the lower gussets.
Weighs about 33 LBS.

[BrendanB]

Looks very nice! To add stability between the transmissions, I'd recommend the cross hex tube from AM that comes in the kit. Extremely light and with a 1/4-20 tap they will attach right where the nuts are on the tops of the gearboxes.

[Mk.32]

I think we do have a few of those shafts left over, sounds like a good idea.
Now all there is left is building it...