Flexible Floating Idler Tensioner
 

I remember seeing a floating sprocket chain tensioner for sale somewhere. It flexed to fit inside a chain run and just floated where it sat. Now I can't seem to find the link to the page on google or here. Anyone have a source? I think 118 used them last year.

Thanks,

Andy B.

Re: Flexible Floating Idler Tensioner
 

I know that a few years ago, Team 1140 got 'em from McMaster-Carr.

Ken

Re: Flexible Floating Idler Tensioner
 

I'm a huge fan of these, they're a bit pricey, but they've lasted us for three years and two robots. :)

McMaster:

5973K1
5973K2
5973K3
5973K4
5973K5
5973K6
5973K7
5973K8
5973K9
5973K11

Re: Flexible Floating Idler Tensioner
 

Not quite what I was looking for exactly. I remember seeing one that flexed to fit inside.

Re: Flexible Floating Idler Tensioner
 

When I looked at 118's robot in Atlanta last year, it looked like they just used a regular sprocket with most of the weight cut out.

Re: Flexible Floating Idler Tensioner
 

AJ R is correct. we took extra sprockets of the same pitch and cut out most of the material for weight. they are pushed into the chain and adjusted by pushing them closer to the drive or driven sprockets.

we have had on a few occasions that the impact forces through the drive train have shattered one of the more aggressively lightened sprockets.

Re: Flexible Floating Idler Tensioner
 

I know what you're talking about. They were some sort of plastic/rubbery sprocket.

I spent a lot of time looking for them a year or two ago, and they only came sized for #35 chain. I thought McMaster had them, but a quick scan isn't showing me anything.

Re: Flexible Floating Idler Tensioner
 

I saw some last year on 597. I'm not sure as to supplier though.

Re: Flexible Floating Idler Tensioner
 

254 used them on our 2003 robot. That was the first time I ever saw them, and I thought they came from McMaster, but I'm not finding them now.

Re: Flexible Floating Idler Tensioner
 

Finally found it:

http://www.renold.com/nmsruntime/sav...D=553&sID=1895

Now i just need to find a place to buy it.

Re: Flexible Floating Idler Tensioner
 

when you do - let us know!! I've seen this during my recent searches too but was concerned that they would fall out with a side impact. maybe the chain tension with the teeth keep them in place?

It also looks like there is only one option for #35 chain and no options for #25. the part number for the #35 is 806 030 01.

Re: Flexible Floating Idler Tensioner
 

Looks like on the last page of the brochure is the USA supplier in TN. I don't know if they sell to the public or retail, but if not, they probably know where.

USA
Morristown TN
Tel: + 1 800 251 9012
Fax: + 1 423 581 2399
e-mail: sales@renoldjeffrey.com

Re: Flexible Floating Idler Tensioner
 

McMaster 5896k1

Re: Flexible Floating Idler Tensioner
 

Thanks!

Re: Flexible Floating Idler Tensioner
 

anything like this for #25 Chain.

Re: Flexible Floating Idler Tensioner
 

Not that I've seen. You don't really need the flexibility. You can use any #25 sprocket so long as it's bigger than both of your other sprockets. You can slide it towards one of the ends for more tension.

We have a kind of weird but still cheap way of making chain tensioners. We buy small sprockets, bore out the hub and put a bushing in. We then buy a mini-bike motor for each tensioner needed and remove the tensioner that is included on the motor. We put the sprocket on where the pulley is. We then mount the tensioner on a piece of angle aluminum which can be mounted inside our drive rail, arm upright, etc...

Total cost is still cheaper than purchasing a chain tensioner. Plus, we have a bunch of 3.5" CIM motors sitting around.

Re: Flexible Floating Idler Tensioner
 

Any pics???

Re: Flexible Floating Idler Tensioner
 

Our tensioners can be seen here:

http://www.wintechpc.com/matt/galler...serialNumber=2

Re: Flexible Floating Idler Tensioner
 

Andy, the problem with that type of spring loaded tensioner is that it only works well in one travel direction. In the case of the pictured robot, if you occasionally shimmed up the gearboxes by putting washers under the base plate mounting bolts, you'd have the chain properly tensioned and wouldn't really need tensioners.

Re: Flexible Floating Idler Tensioner
 

I don't think I understand what you are saying. Our gearboxes are side mounted. Are you talking direction of travel? Because if you angle the tensioners right, it shouldn't matter.

Re: Flexible Floating Idler Tensioner
 

I think I get what he's saying. Think of a bike chain tensioner - it works because you pedal forward so the tension goes from the front sprocket to the back one, and the spring loaded thing picks up the slack.. However, if you try to pedal backwards (imagine that there is no one way ratchet thing for a bike), the tension would pull the spring before it would turn the wheel. I guess it would work if the springs were very strong though.

I hope that made sense.

Re: Flexible Floating Idler Tensioner
 

Didn't notice that you have them attached from the rear. If you were to lift the gearbox straight up, the chains would tighten. That would require a slight slot in the inner frame mounting holes - not much.

A bi-directional chain drive either needs two tensioners, or a provision to snug up the chains such that no tensioner is needed.

Re: Flexible Floating Idler Tensioner
 

Hmm, I wonder how much weight we really save in using #25 chain. This year, to save weight on the tensioners we wound up building the tensioners into already-existing mounts on the chassis, but in return we wound up sacrificing effieciency of the drive train. The power loss from it was enough to merit using an extra pound or two for them next year.

There's an interesting calculation that can be done here to figure out if it's worth it to use #25 chain instead of #35 chain in order to save weight. First, some assumptions (correct me if I'm wrong):

- Ignore mechanical advantage of lighter chain
- Ignore strength advantage of heavier chain
- Ignore the fact that improperly tensioned #25 chain is more susceptible to failure and/or slip during sudden direction reversal or high stress moments than #35 chain
- The rolling chain tensioner will never be available for #25 chain
- Average team with good building skills and capability
- #35 Tensioner listed above (estimated): 2oz. (.125lbs)
- #35 Chain, Weight/Ft*: .23lbs
- #25 Avg Chain tensioner weight: 4-6oz. (.25-.375lbs) -- Assumes usually a bolt, small piece of aluminum, and some plastic composite for the lightest forms
- #25 Chain, Weight/Ft*: .15lbs

Drive Train (4WD omni/mecanum to 6WD all powered wheels)
==================
Avg Length of chain used: 8-14ft
Usual # of chain tensioners used: 4-6, depending on if it's direct drive or not

Therefore
#35
Chain Weight: 1.84-3.22lbs
Tensioner Weight: 0.5-.75lbs
Total: 2.34-3.97lbs

2.34lbs for a mecanum drive and 3.97 for a kitbot modified for 6WD

#25
Chain Weight: 1.2-2.1lbs
Tensioner Weight: 1.0 - 2.25 lbs
Total: 2.2lbs - 4.35lbs

2.2lbs for a mecanum drive, 3.1lbs for highly skilled direct drive teams, and 4.35 lbs for a kitbot modified for 6WD with avg build skill

Manipulators (Arms, widgets, w/e)
==================
Avg Length of chain used: 2-5ft
Usual # of chain tensioners used: 1

#35
Chain Weight: .46-.1.15lbs
Tensioner Weight: .125lbs
Total: .585-.1.275lbs

#25
Chain Weight: .30-.75lbs
Tensioner Weight: .25-.375lbs
Total: .55 - 1.145lbs

Conclusion
==================
We can see that higher skilled teams who have time-tested chain tensioning techniques can really benefit from the weight loss found in #25 chain, but for mecanum drive or rookie/average teams the weight differences are negligible, IMO.

*Reference: http://www.laceyharmer.com/products/rollerchain.htm

Re: Flexible Floating Idler Tensioner
 

Whatever you do, get the best quality chain you can. Maybe something like this: http://tsubakimoto.com/product/drive...class3/10/3/2/