Has anyone used #35 chain sprockets with a West Coast Products single-speed flipped gearbox? One of my fellow mentors insists it cannot be done, and we must use #25 only.
I am skeptical of this assertion. #25 is great and all, but #35 is far more forgiving. Robot weight is not an issue this year.
Why does this mentor think it cannot be done?
There’s no mention in any of the documentation that you can’t use #35 chain (in fact, there’s 0 instances of the word “chain” and only 4 of “sprocket” in the user manual). I suspect the gearbox may have been designed with #25 chain in mind, but I don’t have the ability to open the CAD at the moment and do measurements. I wouldn’t be surprised if there were a smaller maximum teeth on #35 chain, nor would I be if there is a higher minimum teeth on the sprocket to fit around the standoffs.
Even better than #25 or #35, you could use #25H chain. It’s a great happy medium between the two sizes with those gearboxes. Combine with the #25 double sprockets that WCP sells and you should have a rock solid drivetrain. Howerver if you reallly want to use #35 you can do that if you use a small enough sprocket to fit the gearbox.
We’ve used them before and I know there isn’t clearance for large sprockets, but I’d think #35 would fit if you stuck to a smaller sprocket. It’s worth pulling up the CAD model and measuring if you want to go that route.
Wait, what?
@Philso: Beats me.
@Zuelo562: Yes, and one would think the seller (WCP: @R.C ?) would have provided some guidance on this, either at configuration/ordering time or in the user guide.
@CalkinsGarrett We have a ton of #35, and I don’t want to have the tensioning issues we typically experienced with #25. But how small is small enough? 1 tooth?? The goal here was to find someone who has successfully fit an xx-tooth #35 sprocket in there.
@Sparky3D Thanks but I need hard evidence not a thought. If I had CAD I wouldn’t be asking. Old guy mentor here…
@Richard_Wallace Yes, Robot weight is not an issue this year … for our team.
I did ask WCP about this in an e-mail, and Harvey R. responded “I believe you can…”. Sorry, same as Sparky there, I need a yes or no, not beliefs.
Disclaimer: WCP is an awesome company and I just love their products. But for this one specific question all I have so far is no answer, plenty of speculation, and a mild bit of frustration. Capisce?
We used #35 when I was a student in 2017 with our Flipped DS gearboxes, which should be fundamentally similar. Sorry, don’t recall the tooth count.
We’ve used the WCP DS flipped gearboxes since 2019 with 12t #35 chain double sprockets with no problems from the sprockets sizes. Off the top of my head I believe the only difference from the DS & SS is the lack of shifting hardware and output shaft. The #35 chain sprockets should fit just fine.
1807 used 35 chain on a WCP single speed last year and found it to be way more reliable. Only saw one event, but we were breaking 25 chain during week one in 2019. The only reason I could see why you can’t use the 35 chain is if there is an interference issue which I don’t think there should be.
Thank you!
We use #35 chain with that gearbox and have for 3 different chassis systems. The students found it easier to work with and we have not seen it break. Definitely possible.
Were you using #25 or #25H?
It would help to know why the mentor thinks you cannot run 35 chain. We used a design based on the WCP flipped gearbox on our infinite recharge robot. (The real ones were not in stock.) We did use 20 chain though. The only possible problem I see is the output shaft might not be long enough to fit the sprocket and wheels. If so, you can make a new shaft.
Nevermind. We ran our chain on the outside of the tube rather than through the gear box. While increasing the cantilever (bad) it makes maintenance easier and allows for bigger sprockets, decreasing the chain loading.
25 originally but then we switched to 25H. I believe we also broke a 25H chain but I honestly don’t remember. Obviously what chain you chose totally depends on the design. All could be the right choice given certain conditions. 35 was probably overkill but it was nice to never worry about.
I am the mentor in question. Based on CAD, and having placed a 12T #35 sprocket and chain in the model, there is less than 20thou of clearance between the chain and the upper shaft.
(#35 Chain on 12T on the left, and in the background #35 chain on 15T)
I am going to re-model this to be sure of it, but even though clearance is a boolean, that tight is getting too close for comfort.
Just turn down that standoff. Its not that outer diameter because it has to, its that size because it was cheap and easy. I’ve run chain with tolerances in the 0.032 range, it might wear the stand off a little but so what? Also you can get/make 11 and 10 tooth #35 chain sprockets from McMaster Carr as long as you have a hex broach.
Edit: Oh, you said shaft. Still, is it the end of the world if it develops a groove?
I’ve modeled it and measured it more accurately. Approx 0.0063in of clearance. Not something we can hold.
What about using a 10 or 11 tooth sprocket?
We do have broach capability, but time and hands are quite limited for us this year. I would much rather us use as much “plug-and-play” COTS as possible, and spend our machining/manufacturing time on custom parts we can’t buy.
