DIY Roller-blade Chain Tensioner designs?

[LI-ghtcycle]

Hello! I am wracking my brains (what little is still functioning with this nasty flu :lol: ) looking at every example of home-brewed chain tensioners, and since I got a single roller-blade (the mate was missing so I got a discount! w00t!! ... I LOVE Goodwill ) for $3, I am now trying to work out how to attach it, I will get some pics up tomorrow of my build so far (forgot to do that today doh! ) but I'm needing someone with a more functioning brain to give me some 's.

I'm using a 24v 250w Razor Pocket Rocket motor and controller to do the "stoke monkey" style drive using a left side crank with a single speed 52T sprocket and a 16T freewheel on the motor. I could possibly get away with a half link (if they make one for single speed chain?) but I'd really like to have a tensioner regardless since I know in time any chain will stretch some.

So if you have a design you could send my way, even if it's not a Roller-blade wheel, but maybe similar type home-brewed design please feel free!

Thanks in advanced!

 

[etard]

Picture would ne nice, so that we can find suitable mounting locations. Also, alot of poeple use broken derailluers for a cheap fix. You might also want to check the motoroized bike forums cuz those guys go through some of the same issues with chain tensionimg. Maybe you could cut out one of the wheels with part of the rail it is mounted on and mount it onto your seatpost and use a spring and mounting plate that it could slide up and down to keep tension? But this just seems like alot of work as opposed to just buying one of the shelf.

 

[AussieJester]

One i did for my first trike build using one side of brake caliper

KiM

 

[gunthn]

Brilliant!

I wish you were around here last week. I just 'moved' a heap of interesting bikes and parts to seagull mt.

 

[LI-ghtcycle]

Nice Job AussieJester! I long suspected a few tensioners I have seen were built much the same way. :wink: Just curious where you got the cog for the end? I'll post pics soon, I have something of an idea how I might be able to mount it, but nothing that seems solid yet, I keep running into clearance issues with my crank arm.

Picture would ne nice, so that we can find suitable mounting locations. Also, alot of poeple use broken derailluers for a cheap fix. You might also want to check the motoroized bike forums cuz those guys go through some of the same issues with chain tensionimg. Maybe you could cut out one of the wheels with part of the rail it is mounted on and mount it onto your seatpost and use a spring and mounting plate that it could slide up and down to keep tension? But this just seems like alot of work as opposed to just buying one of the shelf.

Well, I understand and agree, only my VERY limited budget does not! :lol: I'm just doing this to keep me occupied until I sell an item or 2 more and or just wait till November when I can afford my geared rear hub motor from Amped Bikes.

But if I can make an ultra light-weight pedal assist e-bike with what I have laying around for the most part, that's something that might help me go up the 7% + hill between me and town.

I can only imagine a 15% + grade like some here have tackled!

This one is only that steep for about a block or so, and then it's maybe 3-5% at different points spread over a mile, but that's enough to get me going slow on my own.

 

[AussieJester]

Nice Job AussieJester! I long suspected a few tensioners I have seen were built much the same way. :wink: Just curious where you got the cog for the end?

its a #25 size sprocket from TNC Scooters You could simply use a standard jockey wheel from a derailleur if your running standard bike chain though preferably one with a bearing not a bush.

KiM

 

[amberwolf]

If you *do* use a jockeywheel, use the biggest one you can, because the larger it is the quieter it seems to roll.

I borrowed AussieJester's idea for my own bike's pedal chain for a bit, since it's kind of wierd and not on the right side with the shifting drivetrain. It had a bit too much slack (and I have no half-link to use), and this fixed it right up. It's also on the *load* side of the chain, for mine, because it's intended to eventually function as the throttle control--the harder I have to pedal, the more motor that gets supplied, so I can just contribute whatever amount of pedalling I pre-set, and the motor does the rest to keep me at the speed I want. (Still working on the hardware for the throttle electronics)

Just at the moment I don't have this tensioner installed becuase the frame has changed, and I no longer have the tube it was mounted to as part of the bike--still working out a different way to do it that won't interfere with anything else.

I will end up using a rollerblade wheel and bearing in place of the jockeywheel, though, because I think it might be quieter. I have a few to test with off of Freecycle. I'll just notch the wheel in the lathe (you can do it on a drill, too), so the chain will stay in the middle of it.

 

[LI-ghtcycle]

Great info and pics!!

I got a few for you all to see now, but, I may have eliminated the need of the tensioner now! :lol:

I was thinking about where I was placing the motor and began to realize I would have less clearance issues and a lower center of gravity with the motor more forward instead of behind the seat.

Previously, I was wanting to take advantage of that unique flat spot in the frame with GT's frame design, thought it would be one of the more stable places to mount the motor, well, it caused more trouble than it was worth so, here's my newest configuration:

As you can see, there is just a clamp holding the motor atm, I will be able to mount some 1/4" (6.35mm) aluminum that I got cheap from a local machinist, going to make a base plate bolted directly to the water-bottle mount, then have another piece of the aluminum slotted with countersunk screws (so the top plate can slide along the base) and I will make the tension similar to a motorcycle's chain tensioner.

It will make more sense when I build it, and I haven't worked out the details 100%, but I am confident I can make it with stuff laying around the shop. In the mean-time, I do have rollerblade wheel trimmed down (ala Y-Pedal style with the drill-press & file! thanks much for the build page!)

Hoping I can get enough motivation (or maybe medication? :lol: ) to be able to continue soon, might need some more tylenol AARRRRGGGGG!! I hate being sick.

 

[John in CR]

Here's a chain tensioner I made using a planetary gear from a Bafang hub motor and a 14t threaded sprocket which I think came from a cassette. I couldn't go with a spring loaded one because I needed to route the top portion of my chain higher. To make it, I used a grinder to get the nylon gear down to the right size and then screwed the sprocket on. I let the gear spin while grinding to make sure it stayed perfectly round. Then I found a bolt to fit the bearing of the gear. To my surprise it's worked flawlessly for about 2k miles. I was going to use a rollerblade wheel until I saw this gear in my parts box, which was going to take a lot less grinding to get down to the right size for the sprocket.

 

[LI-ghtcycle]

Wow! Nice idea there John, I could do the same with a similar idea now that I think about it, I have a 1 3/8" (34.925mm) plumbing test plug making a similar spacer for the threads inside of the 16T freewheel I have attached to the 250w motor shaft (8mm) that looks much like this one, just smaller:

I discovered it by accident at the local hardware store. I just have the washers from the plug on both sides and tightened down the nut so that it's causing the plug to expand, and hopefully it will work good as a "cush" drive so if I hammer the throttle, the chain doesn't take all the abuse. But lets face it, 250w brushed motor isn't going to do a lot of abusing he he!

 

[John in CR]

Don't you need a bearing though?

 

[LI-ghtcycle]

LOL!! yes your correct, Flu brain strikes again!! :lol: :lol:

I'm going to stop posting till I'm a little less under the influence of "Theraflu"