Would love feed back/comments/questions, this time with a WCD.
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.
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.
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.
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?
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.
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
Oh I will definitely look into that, thanks!
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.
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/catalog/bolts/proofloadtensile.htm
A common rule of thumb is designing to 75% of proof load.
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.
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.
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…
I always like seeing a quality base come together, especially with someone so willing and immediate at/to implement suggested changes.
The corner gussets could be 1/16" if you wanted to save some weight, but 1/8" certainly isn’t too heavy and is easier to sell to doubting team members.
Definitly change the bolts on those gussets to rivets.
Incorporate from the get go a very rigid bellypan (as you have no internal crossmembers). Metal is nice but can be heavy unless very thing or heavily pocketed. I’d reccomend g-10/fr4 garolite from mcmaster for a VERY strong and light material that also happens to come in glossy black.
I like the changes you made to the gearbox mounting.
Can we get a close up and/or section view of the outer wheel/shaft/bearing block setup? There is a LOT that can be done right/wrong there that really make or break such a system.
On the same note, what are your plans for tensioning?
The reason the gearboxes are somewhat weakly mounted is if you view them completely from the front/back of the robot. They create a moment tryign to peel them off from teh frame, and you only have bolts at one elevation to react this. You really want bolts at two different heights (it deosn’t have to be much) to react this. Our bolts are only .75" apart vertically and hold up just fine.
Ditto earlier comments about #10-32’s being adequate, our entire drive uses nothing but.
Keep working guys! Very exciting to see, and you’re on your way to a very nice drive.
The key to making a six wheel drive work properly is the stiffness of the frame.
I echo the belly pan idea…if you have access to a waterjet it can be done very nicely…
In the absence of a belly pan you might consider cross members… but remember the frame must be really rigid… in all directions.
Another option to help your frame stay rigid is utilizing the bumpers as part of your rigidity… you might as well use them if you have to have them.
By engineering them into the frame…you can gain rigidity …
take a look at the drive base we posted last week
(1983 is the team number)
We utilize a double side rail… ours is not a West Coast drive like yours…
We also incorporated the bumpers and their mounting into the frame…legally.
I think too many teams don’t think of the bumpers as part of the frame/drive base…rather they think of them as an add-on…
Think of them as integral from the beginning and you can lighten in other areas…
Nice looking CAD work!!
I’ve heard others recommend this stuff too. Any particular thickness that you use? It looks spendy, but if it’s worthwhile then it might be worth an order.
We like 1/16th. Runs like $60 per robot and you get a LOT left over for other parts. Mcmaster btw.
Why rivets over bolts?
I have currently a 1/8 sheet of poly carb in place as the belly pan, is that not stiff enough?
For chain tension, there are pockets for the bolts/shaft in the bearing blocks to allow them to side .25inch.
I will get a photo of the bearing block step up later.
