Chain Tensioning Method?
 

I'm designing the drivetrain for this year's bot and we need a way to tension chains. Last year we used floating idlers from mc master and those were a mess. I'm looking at an automatic tensioning system, such as something spring loaded. Any suggestions, tips, or advice?

Re: Chain Tensioning Method?
 

I would think you could fabricate something like the tensioners that come stock on the large cims. Obviously you would want probably a tighter spring but I'm pretty sure fabricating that would be easy.

Re: Chain Tensioning Method?
 

What problems did you have with the floating idlers from McMaster? Did you use #25 chain or #35 chain?

Re: Chain Tensioning Method?
 

I used 35 chain and just getting the strips, that hold the two blocks together, in to the drivetrain was very difficult and adjusting them was very time consuming.

Re: Chain Tensioning Method?
 

It takes some precise machining but you could use an idler sprocket or friction resistant plastic rod in a verticle slot being pushed up by a spring on either side.

Re: Chain Tensioning Method?
 

Don't use chain?

That seems to be a pretty good tensioning method to me. We aren't going to have a single link of chain on our robot this year.

You could also look at what 254/968 did last year for chain tensioning. I can't exactly describe it, but it tensioned the chain when someone tighted some device. Maybe someone from either one of those teams can clear that up for us.

Re: Chain Tensioning Method?
 

We ordered some large diameter nylon rod from McM, the drive team is pondering some ways to use it, probably cut in half lengthwise, and with a groove turned in it to guide the chain.

Last year's experience showed us that it's worthwhile to spend some time on tensioner design....

Re: Chain Tensioning Method?
 

That device they tightened was something similar to what ive attached below, its the piece i made to tension our conveyor belt last year.

Re: Chain Tensioning Method?
 

There are commercial tensioners as well.

One is an idler sprocket on a bearing, you slide it along perpendicular to the chain somewhere to add tension to the chain

Another is an arrangement just like on the big CIM motor - an idler with bearing, mounted to an arm with a spring (often adjustable tension).

Third are various plastic slides and such, as mentioned already.

McMaster sells all of these.

Don

Re: Chain Tensioning Method?
 

Our take on an adjustable chain tensioner. It was easy to make, simple, not really expensive (cheaper than floaters anyway) and it is possible to spring load them, although we did not. I made a more detailed post about them here.

Re: Chain Tensioning Method?
 

A thick nylon washer on a bolt. Its fool proof to put on, just tension it, and bolt it on. However, you don't want to use them too much.

Re: Chain Tensioning Method?
 

I really liked the chain tensioners that 1625 used on their robot last year. They're great because adjusting the tension is really simple, all you have to do is pivot the little arm that holds the idler sprocket. This worked with their one-chain-per-side configuration.

Here's a picture, and you can see the tensioner right next to the transmission:

Re: Chain Tensioning Method?
 

Here is a great thread on the 254/968 drive train

http://www.chiefdelphi.com/forums/sh...threadid=50318

Here is an alternative design that I came up with that does the same job without the fancy parts. A great render is most of the way down the page.

http://www.chiefdelphi.com/forums/sh...ad.php?t=50768

Re: Chain Tensioning Method?
 

I just did the tensioning system on our robot today, and a simple solution that we are using is basically a small piece of delrin (low friction plastic) pushing down on the chain with two screws tapped into the delrin (yes it actually works..). Then the screws are attached through a part of the frame directly above the chain. Seems to work well so far, going to play with it tomorrow more.

Re: Chain Tensioning Method?
 

That's what we had in mind, making it adjustable through a long range of travel is the fun part! Being able to quickly release the chain tension, and unhook the chain without removing the master link so one can rapidly change a wheel between rounds, is the goal.

Re: Chain Tensioning Method?
 

We're thinking of doing this also this year. We're tired of slots where the axels go, they're a pain. Anyone done the "delrin pushing down on chain with the 2 screws attached to the delrin and chassis" that can offer up any advice or pics?

Re: Chain Tensioning Method?
 

Re: Chain Tensioning Method?
 

thanks for the link, we hadn't thought of that!

Re: Chain Tensioning Method?
 

here's another idea...

http://www.pobcoplastics.com/pg_42.htm

Re: Chain Tensioning Method?
 

We're thinking about designing with a sprocket spacing that allows for the "perfect" distance (exact number of links). There is a spreadsheet to help with this in the CD-media white papers.

I know there will be a little chain stretch, but we're hoping to run without need for tensioners. Anyone have experience with this method?

Re: Chain Tensioning Method?
 

Ok so I got time to take some pics of what I was talking about before. As you can see the delrin block pushes down on the chain. All I need to do to tension the chain more is grab a drill :D.

Re: Chain Tensioning Method?
 

tensionerrrrrrrrrrrrrrrssss :) let me know if you have any questions

Re: Chain Tensioning Method?
 

You could use something like this.
The grey cylinder is a sprocket, and the side plates (blue) bolt on to the KOP pneumatics mounting brackets (green). In our case, we were going to attach a spring of the right tension to the open axle (bottom-left) and to a bolt which would be driven into the top of the mounting block (red) between the Mounting brackets; but you could as easily attach a pneumatic piston, or anything else.


Scale reference: the red mounting block is meant to fit around 1" square tubing.

Re: Chain Tensioning Method?
 

Do you have a rigid mount on your motors/ wheels? if not then put slotted holes, and just push the plates and viola!

Re: Chain Tensioning Method?
 

The last couple of years, we've designed it so we can move the entire motor/gearbox assembly up or down a tad so as to tension the chains. Of course, that is with 2 or 4 wheel drive, not 6. One time, we just cut grooves in some old polyurethane skateboard wheels and used them as tensioners. Price was right...

Re: Chain Tensioning Method?
 

As of right now its not going to be very possible to slot the chassis. These are all really great ideas everyone, thanks so much.