Chain Tensioner Opinions on Modifying the Stock Tensioner, V-Frame Engines

[Email]

Chain Tensioner Link
http://spookytoothcycles.com/images/engines/bearing-tensioner-assmbly.jpg

(I know the tensioner is a problem on these kits... I have read plenty of forums on the problems) I too have been having a problem with the chain tensioner that came with my Skyhawk kit I purchased from Spookytooth. This was the 66cc kit that they stopped selling, probably due to the EPA import restriction. The tensioner keeps sliding back down loosening the chain. To the best of my knowledge the sprocket on the rear wheel is centered; therefore, it is not a wobbly sprocket pulling it loose but instead the tug of the engine on the chain. The freewheel portion of the tensioner will no longer tighten, nor will it loosen (but freely spins and the wheel assembly slides up and down the slot if you wiggle it by hand) so it is stuck moving up or down in the slotted groove on the tensioner housing. I know I have a few options.

The first option is to replace it with the mods mentioned on the forums (with a spring tensioner). Though the problems with spring tensioners are that it makes it more difficult to pedal start the engine.

The second option is to replace the 410 chain with #41 chain and use halflinks and avoid use of the tensioner altogether.

The third option that I thought about after really looking at the setup is to take a small metal bar, drill a partial hole so that the end of the bolt on the freewheel pokes into it (does not have to go through all the way, just grips it enough that it keeps the tensioner at the correct height). Next drill either a slotted hole (where I can adjust the tensioner height slightly) or a precision hole at a distance low enough that the top frame bolt will go through. I know I will have to replace this frame bolt with a longer one.

If I go with the third option there's more that I can do to the bar to help prevent the tensioner from ever going into my spokes. I could make an I-beam with slots on either end that fit onto my rear drop out and bottom bar at a diagonal. In the center I can bolt into the bar I would make for the third option.

Thoughts, opinions? Need a visual diagram/photo? I am not sure whether the third option gives me any advantages over what option 2 would give me, other than it provides another support structure for the chain itself and a mounting point for the chain guard?

Visual:
http://i2.photobucket.com/albums/y27/EmailNBheleu/ThirdOption.jpg

 

[GearNut]

I wish I had a photo of what I am going to try to explain.
some folks weld or clamp a strip of stout flat strap between the chain stay and seat stay.
Determine where the tensioner wheel will rest when attached to said flat strap and cut an adjustment slot in in the strap. Attach tensioner wheel securely, with chain properly tensioned, in slot and ride happy and safe.

Edit:
Another method is to cut the engine's chain down suitably as to not need a tensioner for the engine chain, 1/2 links can help in doing this. If needed, use a tensioner on the pedal chain instead.

 

[Thatperson]

I wish I had a photo of what I am going to try to explain.
some folks weld or clamp a strip of stout flat strap between the chain stay and seat stay.
Determine where the tensioner wheel will rest when attached to said flat strap and cut an adjustment slot in in the strap. Attach tensioner wheel securely, with chain properly tensioned, in slot and ride happy and safe.

I know what you are talking about. I built one for my Uncle's bike. It works a whole lot better than the stock setup.

 

[GearNut]

Thank you Thatperson!!!

 

[Email]

Cheap Quick Fixes

Well I let eagerness get the better of me yesterday. I loosened my tensioner, slid it as far back to the rear wheel as I could and rode it around looking for a piece of my rear rack that had fallen off a few days ago (I remember hearing a pinging sound when I was driving it, but the bike was running fine so I had ignored it, still did not find it). Well the tensioner held up until I got home but when I got back I noticed it was extremely close to the spokes -><- like that much room from being a real problem. Well I loosened it back up again, pulled it back out, tightened it back down and was going to test it when I pulled the clutch to take off(bam) I ripped one of the 12G spoke nuts thru the rear rim and flipped the tensioner all the way to the bottom of the rear dropout. Hindsight, the bottom dropout tapers down back there so there was not enough metal to metal grip to hold the tensioner securely. I am so lucky it happened at home instead of when I was driving around looking for that piece of metal bracket.

Now I have to rebuild a rear wheel (or order one built up). I think the rear hub is fine, but what I would like to get since I have yet to order a front brake hub is to see if someone like huskybicycles could put a wheel together for me. I really would like a 26x2.125 11G or 12G 3W Dyno 90mm Front Drum & a Rear Internal Geared Coaster so once I get the bike going properly I could build some electronics to take advantage of the power coming off the front wheel and gearing off the rear wheel. The only thing that semi-concerns me if I get the tensioner setup corrected is whether the front springer fork will be safe with a front drum brake. I also wish the rear hub had the capability to bolt on a sprocket vs the gasket sprocket method. You cannot get everything you want though. I know the cheap solution would be to replace the rear rim only, but cheap solutions do not always equal the best one. *sigh* back to driving the car again... it will be one to a few weeks before I can put the time back in to fixing it. A lot to think about for version 2, at least I got to get my feet wet and see what this hobby is about (playing with the gas, clutch & pedals on takeoff is fun - and because I love bicycle maintenance <3 the hobby even more). Got some stuff to do before I get that rear wheel though (if that's the option I decide to pursue), as I need to do some measurements (hub width, chain ring position, etc). May just build it on my own, so if it does break the only person I can blame is me.

P.S. ThatPerson - NICE!

Front Wish:
Sturmey Archer: XL-FDD (redrilled for 12G)

Rear Wish:
Sturmey Archer (Measurement Dependent)

 

[arkives1]

opinions on modifying the stock tensioner

I know what you are talking about. I built one for my Uncle's bike. It works a whole lot better than the stock setup.

Please tell me where you found the straps with the rubber sleeve around them? I know I saw them somewhere, maybe on a scooter or electric bike site but cannot seem to find them again. I plan to do one of my cruisers the way you did your Uncle's.
Thanks! Woody

 

[Email]

Rubber Cushioned Loop Straps: If you cannot find them anywhere else, there's always McMaster.
http://www.mcmaster.com/#rubber-cushioned-loop-straps/=79sq08

I wonder if an Idler Sprocket would be better than the stock tensioner, but mounted like ThatPerson did, look at the ones with Wide Hubs(expensive-prob use offset washers and normal sprockets to get correct distance)? If you wanted you could put both one above and one below, would that not reduce chain wiggle?
http://www.mcmaster.com/#roller-chain-guides/=79srvj

(Dyno Links for me later on: Complex Charging Circuit: http://www.nscl.msu.edu/~daniel/sreg.htm)
(E-Werk Charger for USB: http://www.starbike.com/php/product_info.php?lang=en&pid=12413)
(Another USB From Dyno Option: http://www.dahon.com/news/releases/2009/08/dahon-brings-green-power-every-bike)

(#40 vs #41 Chain) - Either work as a replacment to 415 Chain
data of ANSI standard B29-1 (Precision Power Transmission Roller Chains, Attachments, and Sprockets).
ANSI B29-1 roller chain standard sizes
Size Pitch Roller diameter Tensile strength Working load
41 0.500 in (12.70 mm) 0.306 in (7.77 mm) 1,500 lb (680 kg) 500 lb (230 kg)
40 0.500 in (12.70 mm) 0.312 in (7.92 mm) 3,125 lb (1,417 kg) 810 lb (370 kg)

 

[GearNut]

Rear hubs are available that allow you to bolt the rear sprocket directly to them. They are not 3-speed though.http://www.bicycle-engines.com/freewheel-sprocket-axle-wbrake-p-297.html
http://www.bicycle-engines.com/images/images_big/freewheelsprocket-hdaxle-wbrake.jpg

Manic Mechanic can also machine you a custom rear sprocket mount that will clamp around the 3-speed hub of your choice.
Here is an example from pirate cycles, see the top row.
http://www.piratecycles1.com/manic-mechanic-parts.html
They can work with you to insure that the 2 piece adapter will fit perfectly on your 3-speed hub, or you can contact Manic Mechanic directly.
Note that he does these as a hobby so you may have to wait a month or two to get it direct from him.

 

[Thatperson]

I bought the straps at Lowes. Go into the hardware section and go over to where the specialty drawers are and look there. As far as lining up the pulley for the chain, it lined up perfect on the first try. I didn't have to add spacers or anything, you might not be that lucky, but it shouldn't be hard at all to do it. And I can tell you that if you pull this thing into the spokes, something went horribly wrong!

 

[Email]

I bought the straps at Lowes. Go into the hardware section and go over to where the specialty drawers are and look there. As far as lining up the pulley for the chain, it lined up perfect on the first try. I didn't have to add spacers or anything, you might not be that lucky, but it shouldn't be hard at all to do it. And I can tell you that if you pull this thing into the spokes, something went horribly wrong!

Here's the link if you want to write down the item/model numbers before you go to Lowes (Rubber Clamp in Search Pulls it up).
http://www.lowes.com/SearchCatalogD...1&N=0&newSearch=true&Ntt=rubber+clamp&x=0&y=0

GearNut - Thanks for the links! The kit from Bicycle Engines, is that freewheel sprocket the one for the peddle chain or for the motor chain? The Pirate Cycles would work on my Shimano if I have not messed up my hub. Any experience with either kit?