Weird Chain tensioner.

[Aren Siekmeier]

The last two years our team has used short segments of some Delrin rod we have lying around as tensioners. We mount the flat face of a cylindrical segment with a bolt off center, making somewhat of a cam, and then the round face is against the chain. The cam part allows us to just loosen the bolt, rotate the Delrin to retension the chain, and tighten it back up. Depending on the fastening method, the tensioner can rotate slightly when tight, which just means more frequent maintenance, but I think a little Loctite fixes this. This allows for an inch or so of tensioning and is fairly robust and lasts a while if done properly.

Attached is a screenshot of a rough CAD model of it in SolidWorks. The chain runs under the cylindrical Delrin rod, which is mounted horizontally to the aluminum angle which is then mounted to a frame rail or other structural element. You could even mount the Delrin straight onto the frame somewhere if it works out.

[sircedric4]

Originally Posted by compwiztobe

The last two years our team has used short segments of some Delrin rod we have lying around as tensioners. We mount the flat face of a cylindrical segment with a bolt off center, making somewhat of a cam, and then the round face is against the chain. The cam part allows us to just loosen the bolt, rotate the Delrin to retension the chain, and tighten it back up. Depending on the fastening method, the tensioner can rotate slightly when tight, which just means more frequent maintenance, but I think a little Loctite fixes this. This allows for an inch or so of tensioning and is fairly robust and lasts a while if done properly.

Attached is a screenshot of a rough CAD model of it in SolidWorks. The chain runs under the cylindrical Delrin rod, which is mounted horizontally to the aluminum angle which is then mounted to a frame rail or other structural element. You could even mount the Delrin straight onto the frame somewhere if it works out.

We have used this exact same setup ourselves for the two years we've been doing 2992. Also, those two years are the only years that we've not had a chain issue at all. Some sort of tensioner has been a lesson learned for us and something we plan to carry into the future.

As for the original post's floating tensioner, we used two very similar tensioners with great success on our super chain driven 2009 bot. They were made out of white nylon. Since we used them on the vertical positioned chains we didn't even have to move them or maintain them as gravity did that job for us. Here's a photo.

[Aren Siekmeier]

K.I.S.S. !!!

[Aren_Hill]

Originally Posted by compwiztobe

K.I.S.S. !!!

Pssshhhh

[Brandon Holley]

I've built bots with extremely well thought out and elegant tensioners, and I've built bots with no tensioners (using "pre-stretched" chain). The thought out and elegant tensioners did their job, which when they're doing it, makes them almost unnoticeable.

The bots I've made without tensioners have also worked very successfully, to the point where it too was almost unnoticeable.

The point here is that you are addressing the facts and coming to terms with the fact that the chain needs to be tight. Some teams prefer to work tensioner free for one reason or the other. Some teams won't add a chain to a mechanism without a very well designed tensioner in place.

Personally, I think with a tensioner you are covering all your bases and it is the safest/most logical bet. The point of my post is just to acknowledge that the real problem is ensuring a tight chain.

-Brando

[Triple B]

you guys win,
"chains must be tight",
tensioners for everyone.
mike d

[sdcantrell56]

Originally Posted by Triple B

you guys win,
"chains must be tight",
tensioners for everyone.
mike d

Ha your posts never cease to crack me up. I'm also a firm believer in not necessarily using tensioners. The only problem is without perfect alignment you're begging for trouble as a loose chain experiences much more shock loading than a tight chain. In my experiences, we have never broken a 25 chain though even when they were not tensioned properly.

[Andrew Morris]

For at least the last 4 years, we have used various sizes of delrin rods (COTS spacers work too) riding on bolts (in slots or in fixed holes) for chain tensioning on the drivetrain and other mechanisms. This allows for easy adjustment (change OD of delrin) as well as making maintenance easier (remove the bolt and the chain is instantly slack, sometimes so much that you never have to break it).

As for having no tensioners, IMHO it is a pain to get the chain the exact right length and get the master link in, so fast replacements when you lose the chain during eliminations are difficult at best.