White Paper Discuss: Team 179 conceptual - single speed - 3 motor gearbox

[Elgin Clock]

Originally Posted by Tristan Lall

You're welding some of the gears, I see. I'm not a fan of welding, because it can make disassembly a great pain. I'd recommend keyways if possible. (Consider adapting the design for keyways; despite the initial difficulty of putting them in, if you lack a broach, they're very precise and easy to work with.) If you do weld, make sure that the materials are compatible!

Also, the key way option lets the gears stay intact in a high stress situation. In situations like that, the gears teeth will break faster than the weld will, so if you have a couple spare boxes laying around, I would weld them, but keying is much more reliable and easier to change in a breaking situation.

That is one reason we don't weld gears onto shafts anymore.

[Andy Brockway]

I am glad to see that you have taken the plunge to share your design. Your design has pushed the edge for weight and gear load. I design equipment that has to run 10 years in production so I err on the side of strength. Whose design is better? A good design performs its job as intended, if it lasts 10 times longer than needed than possibly too much was spent on it. If it blows up 10 seconds after it completes its mission than it is still a success.

Having said all that, I would like to add some of my experiences and thoughts to help you have a reliable gear box.
-Do not run the FP 32 pitch and Bosch 0.7M to the same gear. The bending moment on the intermediate gear teeth as they run from 32dp to 0.7M will quickly take them right off. Those that ran a 32 pitch gear to the 0.7M actually produced a new tooth pattern.
-The bearings you are using are low grade. This means that there will be some slop as they run. Our 2003 single speed used these bearings on the output and had about a 1/16" play, measured at the end of the output shaft, at the end of the season. Consider what this may do to the 12 tooth gear when making your final choices.
-I recommend using the hex and plastic kit coupling on your output shaft and then having a self supported sprocket/gear output shaft. The reason is that the moment resulting from chains or gears at the distance you are showing from the gearbox bearings may cause movements that are detrimental to the gears. Do not just add one more bearing in-line, this is hard to align and causes a bending action in your shaft.
-Plastic gears: Team 571 ran these successfully in 2004 using Bosch and FP motors. I will be testing this fall using the plastic gear with the Bosch.
-Welding is positive. It also can cause shafts to bend. We have not used welding due to lack of equipment. Last year I used keys and Loctite #609. Loctite advertises that I really did not need the keys (see my note above about how I design)!
-My gut feeling warns me about the 1/8" plates and the small gears. The only way to truly know is to build and test. Our team fights weight every year, this may be a solution.

Build it! When all is said and done the only way to know is to try it.

[Swampdude]

Welded gears - you're pointing out that the key will shear before the teeth come off? I'd like to go with keys, and I don't want to warp the shafts - but back to the intent of this design as cheap and quick, and can it last a few months - maybe not. I haven't checked out that loctite #609 Andy mentions yet. That sounds pretty cool if there's a bond that can take those torques without a key- wow.

Anyhow, this is still more of a risky design, that I want to test to see if like Andy says, will it get me through 4 competitions, not will it run for 6 years. "Cheap and Cheerful" as my colleague puts it.

no 32 pitch on the .7 plastic gear, yah I agree - I think I'm just going to use this as a 2 motor design, as it's original intent. But I might towards the end of it's life throw the FP on there just to see what happens. The nice thing was that to accomodate the FP all I had to do was put a hole in the sideplate.

Shaft output, yah - we used this method off the plastic gearboxes the last 2 seasons just coupling straight out to another bridged/bearing shaft. It wasn't pretty but what we did was shim the motor mounts to the transmission wherever it wound up. But if the design permits I might throw a sprocket right on that output shaft instead of a coupling. The problem with this motor configuration is that you don't have a clear access side since motors protrude from both sides. I like the look of the new Andymarkbiz setup - with both on the same side.

1/8 side plates should be ok since I've got them sandwiched with 6 spacers over a small area. 1/8 plate is tough stuff. Unless we do put the sprocket right on the output shaft, then she'll see some much more significant loads.

I know my views on all this make conservative folk cringe but I think if it works it's all worth it- Come on you gotta admit it

Thankyou guys for your input, it's all very helpfull. I'll be sharing it with the build team.

[Swampdude]

Good so the stock carbon steel 24 pitch gears work :-)
I think I'm going to switch the bearings to the Sintered Bronze, Oilite flange bearings on Small parts - those things are $1.50 ea.
also going to look into the #609 loctite for gear bonding vs. welds
Now we're talking!

[MattB703]

Originally Posted by Swampdude

Good so the stock carbon steel 24 pitch gears work :-)
I think I'm going to switch the bearings to the Sintered Bronze, Oilite flange bearings on Small parts - those things are $1.50 ea.
also going to look into the #609 loctite for gear bonding vs. welds
Now we're talking!

I strongly recomend staying with roller bearings. I have seen may teams learn this lesson.

The way I look at it, we are all limited by the amount of energy we can put into our motors. A design that has less parasitic losses will put more of that energy to the ground.

Matt"s
$0.02