Weird Chain tensioner.


I’m designing a standardized Drive Train that will hopefully be used in many subsequent years for my team.

It is a 6wd, using 35 chain.

I came across this chain tensioner: McMaster-Carr part # 5896K1,

Has anyone used these before? How well do they work?


Some people might refer to that as a floating tensioner. Many teams have used them in the past and them seem to work well in the right application.

We used them on an arm chain once and it worked well, but with a long run flexing from quick direction reversals can cause them to fall out. We added a retaining system.

I would also recommend using this. It works quite well, and be used in more than the way shown. :wink:

Just wondering, can I get a peak at this drive train? :slight_smile:


Thank you. Yes, There would be a retaining system: the main structural supports for the DT would go straight through the floating tensioners.

Formerly Famous: Once I have it CADded, sure, i guess…

We’ve used similar floating idlers machined out of .125 Lexan for 25-pitch roller chain. As long as you pay attention and keep adjusting their position until the chain stops stretching, they work great.

We actually made our own version of the AndyMark style, without the rubber band fingers, but still using the zip ties, and it worked quite well.

There is another page of chain tensioners at McM-C, with a more expensive and sophisticated variation of the AndyMark one:

Go to page 1022, or part number 5973K2

You can eliminate the need for a chain tensioner if you preassemble the sprockets and chain than measure the distance to center, than build the distance into your frame. As long as you only have two sprockets in each chain set it’s a piece of cake. This will also save some weight.

I’ve found that this only works for chain runs with a center-to-center (CTC) distance of less than about six or so inches for 25-pitch chain. If using 25-pitch roller chain with CTC distances of greater than about six inches, chain stretch becomes large enough that it can cause performance issues without a chain tensioner.

In the past couple of years, we have built in quite a bit of tolerance in they way we mount our transmissions and motors. We will usually have slotted holes in our chassis for mounting, allowing us to adjust for small amounts of chain stretch.

We have not determined whether or not this affects performance or autonomous.

That sounds good for a six wheel drive, three wheels with a motor and gears between each wheel.

" O o O o O "

This can also be done if you have an extra sprocket laying around that is larger than the two sprockets that your chain is running on. We’ve called it the floating sprocket - it’s a real quick way to tension your chain if you’re in a pinch and it works surprisingly well.

but usually if you plan for it and buy some “add in” masterlinks which is a half a link you can usually be close enough to make it without tensioners, and you can determine if you need them as you build the chain

For a drive base with skid steer & direct drive for your center wheels I would agree with “joeweber” that there is no need for chain tensioners. When the chain stretches to a length you deem too loose, then change the chains out. The tensioner may give you the illusion that your chains are in good condition when in fact the chains are still stretching you just dont know how much. Dont get me wrong, tensioners are nice but in my experience they are not always required. But I also like #25 (1/4") chain for everything.
mike d

At about $3/ft, throwing away stretched roller chain is a more expensive endeavor than installing a $0.50 chain tensioner.

Waste not, want not.

Would it be cheaper over time to break the chain and pull out a link, if this happened more than once?

our team always uses bicycle chain and i don’t know what that is different, but the bicycle chain seems to work well even when semi loose, at least in one direction.

you would have to remove at least 2 at a time and add in a half link, depending on the type of half link, you might have to remove three. Also, the chain might not stretch an entire link before it needs to be fixed. thus, you use a tensioner.
Of course, if there was considerable stretching, removing a section of chain would make sense.

Unless the chain stretched a full two links, it’s time consuming to take apart and would require the use of a half-link. A well designed chain/belt tensioner integrated into the rest of the system adds on a few ounces of weight, and can be tensioned in seconds.

I was not saying to waste chain, but with or without a tensioner, the chain stretches close to the same amount. I would rather change the chain when it is determined to have stretched a given amount rather than to keep tensioning the chain until it fails. In my past experience, I believe having a chain fail during a match is priceless and would much rather spend the $3 per foot on chain. Each year we have used the same chains for two regionals, Atlanta, several off season season events, and quite a bit of testing with zero problems. This has been the case over the last 4 seasons and our 2008, 2009, and this years robot all have the original chains from build season.
mike d