Check out 701s shifting tranny..

[Salik Syed]

Hi check it out ...
this is our tranny i try to make it as small and compact as possible but i don't know it kinda gained some weight after some ajustments... you can put the sprocket on the outside or the inside... can i get some comments on it? good design or bad ?

[Tom Bottiglieri]

how is the CIM mounted?

[Bill Gold]

How is the CIM motor mounted to the transmission? It appears to just be hanging out there in space.

What’s that extra aluminum plate that the FP (I assume) motor is mounted to? That’s just another plate you’ve got to machine, when you could use the orange outside plate to mount to, if you rearranged a few things.

I, personally, like the usage of 1/8” plate.

It appears that you’re extending the 8mm output shaft from the CIM motor. If this is so, what does your adapter look like on the inside? I don’t know… I would try to avoid this, if at all possible. It just seems like it’s asking for trouble, and it seems like it’d be hard to repair if it failed at an event.

Also, if you wanted to machine the dog-shifting area on just a manual mil (if you’ve got access to one) I would suggest going to a square shaped dog, like Team #716’s transmission (among others). It seems easier for students to machine, but if you’re sending it to a shop for them to build you don’t have that problem.

I think you could get away with a thinner dog, thus reducing the size and weight of the transmission, too.

It looks good, though. You’ve got a great step on a lot of teams having gone through this designing already. Good luck on your revisions and eventual fabrication (if you go with a derivation of this design).

-Bill

[Andy Baker]

Salik,

This is a good start of a design. As I have said before, it takes guts to put your design on here to be critiqued, as you will get some constructive criticism in this thread.

Like Bill, I like your use of 1/8" thick walls. I like your angle too, as it makes the gearbox easy to mount. Your gear reduction between the F-P motor and the CIM motor is a good idea also, but it needs to be implemented better. You dog pockets on your 2 gears are good, but you will need a CNC mill to implement this shifting technique.

Here is a short list of improvements that you may want to implement. Please don't take this has harsh criticism, as I am only trying to help.

1. Getting wires to the F-P motor will be difficult. If you shorten the angle bracket on the right and give clearance around the F-P motor, your wiring will be easier. Also, once you shorten that bracket, you can bring the two brackets together and reduce the width of your gearbox.

2. As said above, you need to mount the CIM motor in a different way. This mounting will be difficult with the F-P gear and the CIM gear the way they are.

3. Can you choose a smaller F-P gear? That will allow you to omit that little sup-plate that you used to mount the F-P motor. You would need a small enough gear that allows you to access the 2 mounting holes for the F-P motor.

4. The cylinder standoff for the dog shifter will work well with only 2 posts. You have 3, and that will work, but it is a bit of overkill.

5. The dog shifter gear can be shortened. However, yours will work fine. It is good to have dog teeth that are too long as opposed to too short. If you are trying to reduce the width of your gearbox, this is an area make smaller, but it is not necessary.

6. The two gears, inside the gearbox, on your CIM motor shaft need to have a wider face width. It looks like they are currently 1/4" wide. They really need to be 3/8" wide, in my opinion. This way, you will get the full mesh onto your bigger gears.

Like I said above, this is a good start. I commend you on posting your design.

Sincerely,
Andy B.

[Elgin Clock]

Originally Posted by Andy Baker

1. Getting wires to the F-P motor will be difficult. If you shorten the angle bracket on the right and give clearance around the F-P motor, your wiring will be easier. Also, once you shorten that bracket, you can bring the two brackets together and reduce the width of your gearbox.
Sincerely,
Andy B.

Andy, or anyone else for that matter..

Will the location of the F-P/Drill (whatever that smaller motor is) potentially cause an electrical arc between the back leads of the motor and the angle plate behind it??

I'm sure the connector will initially be well insulated and taped up with some electrical tape, but we all know how much beating/wear that gearboxes and the overall robot take during a full competitive FIRST season and beyond..

Worst case scenario of course... Tape comes loose, or frays, and motor terminals arc?? Is it a possibility?

Idk.. I could be wrong. Maybe there WAS a valid reason it took me 3 times to pass an intro to Electrical Applications class.

[Cory]

Originally Posted by Andy Baker

You dog pockets on your 2 gears are good, but you will need a CNC mill to implement this shifting technique.

Well... If you have quite a bit of time and patience on your hands, you can do it with a manual mill and rotary table. I worked with a machinist at one of our sponsor's last year, and we made both the dog, and the pockets in the gear this way. It was VERY tedious though, and by the end we were both wishing we had a CNC machine.

[Salik Syed]

Originally Posted by Cory

Well... If you have quite a bit of time and patience on your hands, you can do it with a manual mill and rotary table. I worked with a machinist at one of our sponsor's last year, and we made both the dog, and the pockets in the gear this way. It was VERY tedious though, and by the end we were both wishing we had a CNC machine.

we have both a rotary table and cnc machine so that shouldn't be too hard.... we are still kinda figuring out the CNC though....

The CIM is mounted with the mounting bolts, there are some spacers to keep the motor away from the plate so we could have room for the gear... the spacers are not drawn in....
i would make the FP gear smaller but then i'd have to make the CIM gear smaller and then the FP would intersect with

[krhs_programmer]

hey do you have a copy of that assembly and all its parts for inventor that i could look at because the concept of it is cool and i want to learn from it.

[Salik Syed]

i'll release a Cad file some day but not yet however..... i guess you should look at the AM shifter they have cad files for that and it is definitely a more proven design.... i think the site is www.andymark.biz

i think we will soon begin fabrication of the tranny... any last minute comments LOL.... with our CNC mill we should be able to churn these transmissions out quickly enough.... maybe 1-2 hours a plate... the gears will be hard to do since they are stainless steel

[coreyjon]

Good luck with your transmission (both in design, and function). In the years that I've been doing this, I have always been involved with the "drive & chassis" in some way. Last year it was by building the transmission, and this year I did design a transmission (and a few variants of it). but a few weeks ago we stumbled across this nice 4 speed automatic, and I'm working up a prototype of that (it had 4 speeds, but I have an idea for adding a high low range). So, the driver can choose between normal range,and a lower range for some more pushing power. It would be similar to a tractor. Giving it in effect, 8 different gear ratio's. Stick with drive and chassis, and keep working on designs. Also, whenever you get the chance to do some of the machining, do it, it's a great thing to know. I myself have been the lead machinist student on the team, as said above last year I build the tranny's, and then I also designed, and built the winch. I go to school for mechanical engineering, but all my free time (what little I have) you can find me in the machine shops.

Good Luck, I look forward to seeing you design come to life.

[Salik Syed]

I was thinking about shortening the plate so it doesn't block the back of the FP ... however since this transmission will be completely exposed... i don't want another robots appendage pulling out FP wires or whatever...
the transmission is going to be mounted between two pieces box and the wheels inline with the transmission (the sprocket is housed w/ in the transmission)

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The parenthesis with dots represent the wheels.