Sparky 384: Custom DS Transmission (2014 Offseason Project)

[Fearthewookie]

Hello all,

Attached is a quick look at Sparky's new custom transmission developed during the 2014 off-season. Included are a few renders of the CAD model and a picture of our completed prototypes.

Info:
- Dual speed (8.5 fps low, 18.5 fps high)
- 3 cim
- Integrated belt-driven encoder
- Multiple ratio options available
- Compact & lightweight (.32 lbs per aluminum plate)
- Designed for easy integration with Sparky's modular West Coast style drive rails

Input and questions are always welcome.

Good luck in 2015!

[wilsonmw04]

I would love to see the STEP files for this. Will they be forth coming?

[E_puello]

By having a gear in between the top cim and the first stage aren't you gonna get some funky speed differences between your gears? :confused:

[thatprogrammer]

One gearbox has an additional blue part http://www.chiefdelphi.com/forums/attachment.php?attachmentid=17702&d=1420242986
Was is the function of this?

[chadr03]

By having a gear in between the top cim and the first stage aren't you gonna get some funky speed differences between your gears? :confused:


No this will just change the required rotation of the motor. Idler gears will not effect the ratio.

[Sparkyshires]

I would love to see the STEP files for this. Will they be forth coming?

Yeah, they should be up within an hour or so. Definitely before kick off.

One gearbox has an additional blue part http://www.chiefdelphi.com/forums/attachment.php?attachmentid=17702&d=1420242986
Was is the function of this?

That's a 3d printed encoder mounting bracket.

[Fearthewookie]

Sorry everyone, here is the .STEP file. Simply click on the link and download:

https://drive.google.com/file/d/0B1Z93B7fchWBR2daNXNheFB3aVk/view?usp=sharing

[wilsonmw04]

Thank you for the files.

[dellagd]

Looks great guys!

Maybe this is the normal practice, but I hadn't thought to group all of the Powerpoles for all three motors into one connector before. Very tidy.

[vps]

Random Question:
Which CAD software do yall use?

[Madison]

The additional retaining ring groove in the output shaft gives me the heebie jeebies. That's an immediately obvious, clear point of potential failure, so keep an eye on it.

[Fearthewookie]

The additional retaining ring groove in the output shaft gives me the heebie jeebies. That's an immediately obvious, clear point of potential failure, so keep an eye on it.

Hi Madison,

Im not sure I understand, which specific groove on the output shaft? Why does this worry you?

Thanks

[Fearthewookie]

Random Question:
Which CAD software do yall use?

Solidworks 2013-2014. Currently we are between the 2013-2014 and 2014-2015 versions.

[Fearthewookie]

Looks great guys!

Maybe this is the normal practice, but I hadn't thought to group all of the Powerpoles for all three motors into one connector before. Very tidy.

Hello!

Im not sure this is common practice either, but due to our modular West Coast style drive rails (our drive system unbolts from the chasis in order to allow for maintenance or emergency swap-outs), our transmissions need to be easily disconnected. We found this is the best and cleanest way to do so.

I am including an image of our modular system used at 2014 offseason competitions. The transmission pictured is last years custom one speed. (its beige simply because it was an r&d project). This was taken during a dissassembly to train new members, so the middle wheel is of course missing.


Thanks

[Fearthewookie]

Thank you for the files.

Of course!

[wilsonmw04]

Can you give me the total weight of this gearbox?

[Sparkyshires]

Can you give me the total weight of this gearbox?

Very light. I'll wait for Brooke to chime in on this one as I don't know the specifics, but due to the cheesing (HA!) I want to say around ten pounds.

[Fearthewookie]

Can you give me the total weight of this gearbox?

Hello,

I cant say exactly due to the fact that my memory is horrible, but I will weigh it hopefully tomorrow and get back to you. I do know that it is less than you would expect it to be, I was surprised at it.

[Lil' Lavery]

Looks great guys!

Maybe this is the normal practice, but I hadn't thought to group all of the Powerpoles for all three motors into one connector before. Very tidy.

Tidy, yes. However, large banks of powerpoles are also much more difficult to plug and unplug.

[Fearthewookie]

Tidy, yes. However, large banks of powerpoles are also much more difficult to plug and unplug.

This can be true but we dont have too many issues with it ourselves (the largest powerpole bank we use is the one you see in the picture). The main problem with those Anderson powerpoles is installation xD They can be a real pain.

[Madison]

Hi Madison,

Im not sure I understand, which specific groove on the output shaft? Why does this worry you?

Thanks

I'm speaking of the innermost of the two retaining ring grooves turned into the output shaft. Folks will often put two retaining rings onto a shaft if they're training to constrain something axially, which appears to be what you're doing here.

The retaining ring groove, though, is a point of stress concentration in the shaft. You're presumably transmitting torque through the groove -- perhaps to a wheel or set of power transmission components -- and doing so can lead to a failure of the shaft at the groove.

[asid61]

Looks pretty neat. Is the encoder mount and custom output shaft stuff the only change to the normal WCP gearbox?

[Fearthewookie]

Looks pretty neat. Is the encoder mount and custom output shaft stuff the only change to the normal WCP gearbox?

Hello,

No, it isnt. We did base the hole patterns off of the WCP gearbox so that way we can use the same gear ratios available COTS (saves time and money), but some of the geometry is different (the overall dimensions are different and the plates themselves are different). Our custom transmission is shorter and a little bit thicker than the WCP DS. The way our transmission mounts onto the 1" x 2" tubing is also different. The tolerances on the pressed bearings have also been changed to allow for a much better fit (no way those puppies are coming out). Some changes will also be made after kickoff to allow for motors and their pinion gears to be swapped out without having to take apart the transmission (something that is an issue with the WCP gearboxes). If you closely compare the two the differences will start becoming more apparent.

Thanks

[Fearthewookie]

I'm speaking of the innermost of the two retaining ring grooves turned into the output shaft. Folks will often put two retaining rings onto a shaft if they're training to constrain something axially, which appears to be what you're doing here.

The retaining ring groove, though, is a point of stress concentration in the shaft. You're presumably transmitting torque through the groove -- perhaps to a wheel or set of power transmission components -- and doing so can lead to a failure of the shaft at the groove.

Hi again,

I understand what you are saying now. Thank you for your input.