Chain Drive

[daveimi]

To chain drive a heavy. Is it a case of having a wheel with a sprocket on an axle, and a motor with a sprocket on the shaft. And then you buy the right chain for the sprockets, and use a chain splitter to fit the chain?

[Shooty]

As far as I'm aware that should be the case. If you want to see a drive system more in depth Matt Maxham has a brilliant video diving into his bot Sewer Snake, and it shows off his drive system, which has to be one of the most effective ever built in robot combat: https://www.youtube.com/watch?v=Pt6_dXKwQYw

[team death]

Hi Dave
You might also want to look at our build diary entitled Team Death-New Heavyweight
we cover the pros and cons of sprockets and chains including reducer units for different
ratios.
Your basically correct with your opening sentence, the most important thing
though is the ratio
Eventually we settled for a 8 to 1 which worked very well and I would recommend.
So for every 10 teeth on the motor sprocket you would have 80 teeth on the drive.
Of course in the real world you use a reducer sprocket with 20 teeth so only 40 teeth
are needed on the drive.
This can be quite complicated and that's why many Roboteers settle for gearboxes.


I was forgetting our Robot did have rather large back wheels so if you use
8 inch wheels you would probably get away with 10 teeth on the motor
and 40 on the driven wheel giving a 4 to 1 ratio and no reducer needed.
I woulden't go less than 4 to 1 even if your wheels are smaller than that.

[Theo]

I'm not an expert on reductions, but Craig Danby once said to measure the diameter of the wheel in inches, add a couple more, then that's your reduction. Was a while ago, but it's a pretty reliable rule of thumb

[shakesc]

Chain is a bit heavier but has a bit more tolerance to misalignment to belts
ratio is easy - number of teeth sprocket a / number of teeth sprocket b

You need to calculate the sprocket distances carefully if you want to avoid a tensioner - assuming its a relatively short run
Chains will have a bit of stretch - give some ability to tension the chain e.g. slotted holes for the motor mount

I learnt alot with Spur 2 on sprockets and chains, it didnt put me off be makes me think a bit different!

Have a look at
http://www.revrobotics.com/content/d...cket-Guide.pdf

[daveimi]

Oh yeah I never thought about a chain reduction needing spot on alignment. Thought it would be a dead easy drive train for a heavy, but I spose it's still loads easier than mod 2 gearing etc to get right.

[team death]

Chains and sprockets can be quite forgiving as long as they are not miles out
I did most of my allignment by eye and a simple set square.
A great source of chains and sprockets to keep costs down is to use lawnmower
bits-they are usually heavy duty and just a few quid.

[Triceratop]

Hi, just thought I'd throw my two pennith in.... stay away from #25 chain (mini moto). The chain is very strong and sprockets quite small due to the pitch but the chain is not forgiving on misalignment - as I found out. I would suggest a form of tensioner even if it lays on the chain, that will help keep the oscillation down which if left can result in chain jump off the sprockets.

[daveimi]

Oh cool thanks! Thanks for all the guidance.