SprocketR - Custom Sprocket Web Application

[Chak]

Cool! I have a couple of questions:
1. The chain sizes are in inches and the c2c distance is in mm . What's the reasoning behind that? Can you make an option in inches?
2. When would you want slack in your chain? I've heard that some people add a little bit of c2c distance to get tighter chain.

[ERothfus]

The main SprocketR developer is deep in finals this week, so I thought I'd go ahead and respond. I'm one of the mentors working with the Chap Research team on SprocketR.

>> 1. The chain sizes are in inches and the c2c distance is in mm .
>> What's the reasoning behind that? Can you make an option in inches?

We don't have a lot of options in SprocketR yet. Things are rather hardwired to mm right now. We intend, though, to make "units" an option in the future. For chain, we just used the "industry" designation of #25 and #35, which aren't really in inches.

>> 2. When would you want slack in your chain? I've heard that some people add a
>> little bit of c2c distance to get tighter chain.

There is an "best" amount of slack for a chain that promotes the best wear on the teeth on the sprocket...which is particularly important for SprocketR given that the resultant teeth are made of plastic. Further, a bit of slack allows the chain to position itself on the sprocket during uptake, where an absolutely tight chain may bind, again, particularly on a plastic sprocket which isn't as rigid as a metal sprocket and may not be perfectly flat under a load.

SprocketR bases calculations on the "perfect" or "ideal" chain length, which is not attainable since a real chain's length is a multiple of the length of a single chain link. So SprocketR rounds-up to the nearest chain link length taking into account the desired slack.

Having said all of that, you can absolutely specify zero slack if you want, though you're likely to get just a bit of slack anyway since the chain length will likely be longer than the "ideal length" given that it must round up to the nearest whole link length. We have found that 1% is an appropriate target chain length, which is the program's default.

[thinker&planner]

Looks great! I can foresee frequent visiting in my future.

I have one suggestion: Have a minimum/maximum gear ratio, or incorporate some sort of tolerance. think

Also, I'm not sure if this is the intent of the project, but you might consider an option for outputting the 2d profile for lasercutting or waterjetting.

[Jared]

Looks really cool - it saves me from having to go to SDP-SI to track down step files of sprocket geometry, which can be a pain sometimes. I also like the preview ability to see roughly the size of the sprocket.

Originally Posted by ERothfus

For chain, we just used the "industry" designation of #25 and #35, which aren't really in inches.

#25 chain is 1/4 inch pitch and #35 chain is 3/8 inch pitch exactly, which is what is used in industry.

There is an "best" amount of slack for a chain that promotes the best wear on the teeth on the sprocket...

Which is the exact center to center distance! If you ask sprocket/chain manufacturers, they'll tell you this. If you are just rounding to the nearest chain size, it will not work very well - the chain will jump, possibly coming off the sprocket or breaking teeth.

Having said all of that, you can absolutely specify zero slack if you want, though you're likely to get just a bit of slack anyway since the chain length will likely be longer than the "ideal length" given that it must round up to the nearest whole link length. We have found that 1% is an appropriate target chain length, which is the program's default.

How did you find that 1% was the right length? Also, when I choose 0% slack, it still gives me 3.598 slack (chain links) and tells me "Distance from Desired Slack (chain links)" is zero.

[ERothfus]

Slack is definitely a big issue, and we feel it potentially gets more "delicate" which you have plastic sprockets, which is one of the reasons that SprocketR exists - to find the right target for you. We believe like you that a tight chain is a good chain, and the industry seems to have some guidelines too.

• http://chain-guide.com/basics/7-1-2-1-chain-slack.html
• http://chains.ustsubaki.com/Asset/Drive-Chains.pdf
• http://www.renoldjeffrey.com/nmsrunt...=1029&sID=2750

Our percentage measurement isn't done, however, like these references suggest. We provide a slack relative to the overall length of chain. The 1% is our attempt at a useful slack that doesn't provide a loose chain that can jump. However, we don't have a bunch of empirical data...yet...that's one of the reasons we have the SprocketR out now! We'd like to use a bit of crowd-sourced testing.

Also, when I choose 0% slack, it still gives me 3.598 slack (chain links) and tells me "Distance from Desired Slack (chain links)" is zero.

Yikes, sounds like a bug. Can you provide us with information to duplicate it? We can take bug questions/data off of this forum and move it to SprocketR@ChapResearch.com, however.

Thanks for the help! We want to make the SprocketR as useful as we can.