pic: WCD Sheet Metal Concept Chassis

[GarrettF2395]

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[Edoc'sil]

Looks sharp, where are the wheels from and what cad did u use, the render looks sharp

Very very nice! I've got a design that's quite similar to this brewing.

Out of curiosity, why drive the rear wheel, instead of the middle wheel? I've always found that it's easier to distribute the weight of the base when it's centered.

I really dig this design. Keep plugging at it!

[Hawiian Cadder]

if you are going to do this make sure that the chain is not going through a tube, my team did something exactly like that for 2008 and it ended a very badly, we dremeled at least 5 holes in the cover at competition in order to fix it. also, be sure to leave a lot of space between the chain and its cover, otherwise when in operation the chain vibrates just a little bit and hits the cover. as long as you dont have those issues, that drive looks fantastic.

[Edoc'sil]

How would you tension the chains? Will you just CAD them to be the right distance apart?

[ttldomination]

I have a question in general about the WCD system, are you using generic bearings/bushings int he sheet metal for the axles, or are there some special ones?

[Rion Atkinson]

Originally Posted by Edoc'sil

Looks sharp, where are the wheels from and what cad did u use, the render looks sharp

I CADed the wheels a few weeks back, the entire thing was done in SolidWorks.

Originally Posted by Edoc'sil

How would you tension the chains? Will you just CAD them to be the right distance apart?

The tensioning system will be spring powered so that we wont really have to check on the chain too much.

Originally Posted by Hawiian Cadder

if you are going to do this make sure that the chain is not going through a tube, my team did something exactly like that for 2008 and it ended a very badly, we dremeled at least 5 holes in the cover at competition in order to fix it. also, be sure to leave a lot of space between the chain and its cover, otherwise when in operation the chain vibrates just a little bit and hits the cover. as long as you dont have those issues, that drive looks fantastic.

When you say don't take the chain through a tube, what do you mean? Would the in side the side channel there count as your tube?

Originally Posted by ttldomination

I have a question in general about the WCD system, are you using generic bearings/bushings int he sheet metal for the axles, or are there some special ones?

Because WCD are done with live hex axles most of the time, teams use bearing blocks and then hex bearings. I can't remember who right now sells the bearing blocks(AndyMark?), but I do remember that AndyMark sells the bearings.


Garrett, it looks awesome.

[GarrettF2395]

Originally Posted by CraigHickman

Very very nice! I've got a design that's quite similar to this brewing.

Out of curiosity, why drive the rear wheel, instead of the middle wheel? I've always found that it's easier to distribute the weight of the base when it's centered.

I really dig this design. Keep plugging at it!

Thanks Craig!

I have a few reasons for going with the rear direct drive.
-I wanted to start off with a good majority of weight behind the middle wheels in order to
reduce the amount of rock the chassis experiences while driving.
-I also wanted the maximum amount of open mounting space for electronics without the gearboxes getting in the way.
-With this design I'm able to put the battery closer to the center of the chassis, which
helps a lot in balancing things out, and since the battery weighs more than the shifters, its
placement on the chassis is more critical (at least in my opinion).
-And of course... because it looks cooler

Originally Posted by Hawiian Cadder

if you are going to do this make sure that the chain is not going through a tube, my team did something exactly like that for 2008 and it ended a very badly, we dremeled at least 5 holes in the cover at competition in order to fix it. also, be sure to leave a lot of space between the chain and its cover, otherwise when in operation the chain vibrates just a little bit and hits the cover. as long as you dont have those issues, that drive looks fantastic.

I already took this into account. The chain is fully accessible from the bottom of the robot, there
is more than enough distance from the chain to the rail, and my chain tensioner (coming soon)
will help hold the chain away from the rail itself just for added protection.

Thanks for the advice though

Originally Posted by Formerly Famous

Because WCD are done with live hex axles most of the time, teams use bearing blocks and then hex bearings. I can't remember who right now sells the bearing blocks(AndyMark?), but I do remember that AndyMark sells the bearings.


Garrett, it looks awesome.

Thanks buddy!
Though most teams make their own bearing blocks for their chassis, team221 sells them, and yes the hex bearings I used are AM's.

[Chris is me]

Originally Posted by Formerly Famous

The tensioning system will be spring powered so that we wont really have to check on the chain too much.

Spring loaded tensioners are notoriously unreliable. I would suggest the "traditional" west coast tensioning method of sliding bearing blocks, or possibly a nylon / delrin sliding standoff for each chain section.

When you say don't take the chain through a tube, what do you mean? Would the in side the side channel there count as your tube?

I would prototype a scale version of this drive and figure out how serviceable the chain is through the completely open bottom hole.

I like this drivetrain... reminds me a lot of Vex.

Now for my design questions... I have no experience, so these comments are worthless. Would it make sense to add some fillets to the triangular cutouts in the sheet? What if you had the inner flange bend in toward the chassis, so you could rivet the belly pan to it? This would also increase the serviceability of the drivetrain by giving you more access to the chain.

[JesseK]

Originally Posted by Chris is me

Spring loaded tensioners are notoriously unreliable. I would suggest the "traditional" west coast tensioning method of sliding bearing blocks, or possibly a nylon / delrin sliding standoff for each chain section.

I would think that most FRC spring loaded tensioners are unreliable due to lack of understanding in the design. A standard bicycle has used spring loaded tension for who knows how many years how, even with a shifting drive system. Yet teams who put them in on a 2-way torque transferring system must account for both directions, whereas a bike tensioner only has to deal with one. Thus, a team could easily make a spring loaded tensioner reliable so long as the design is sound. The mini-bike motor belt tensioners from 2006 would be a good place to start experimenting.

As for the CAD render: if the side rails are open on the bottom for chain accessibility, are there supports on the inside of the rail to keep it from buckling in on itself? The channel shown in the reflection of the render makes be believe the side rails are very prone to torsion.

I also like the rear-wheel drive; Drop-center drive train designs are TOO easily turned if the weight is close to the middle, so putting most of the drive train/electronics weight towards the back allows for more flexibility in weight distribution when designing manipulators. The tradeoff is less maneuverability if a chain comes off or breaks.

[Rion Atkinson]

Originally Posted by JesseK

I would think that most FRC spring loaded tensioners are unreliable due to lack of understanding in the design. A standard bicycle has used spring loaded tension for who knows how many years how, even with a shifting drive system. Yet teams who put them in on a 2-way torque transferring system must account for both directions, whereas a bike tensioner only has to deal with one. Thus, a team could easily make a spring loaded tensioner reliable so long as the design is sound. The mini-bike motor belt tensioners from 2006 would be a good place to start experimenting.

... The tradeoff is less maneuverability if a chain comes off or breaks.

I started a thread on here about spring chain tensioners. We decided through it that with some good designing and testing we would be able to make a decent chain tensioner that would work both ways.

[JamesCH95]

Looks good! I like your design. I would, however, encourage you to put the transmissions in the middle. It will help the chassis' ability to turn both from an inertia standpoint and from a "reducing scrub" standpoint.

How are the sections fastened together?
O'all weight?

Just a thought: some nuts like these fastened on the inside of your drive modules might be a great way to tie components/chassis elements together.

http://www.aircraftspruce.com/menus/ha/nut_anchor.html

I realize Aircraft Spruce isn't the cheapest place to buy things, but it's the first source that came to mind.