EZ as Pie Chain Tensioner

Discussion in 'Transmission / Drivetrain' started by Timbone, May 5, 2016.

  1. Timbone

    Timbone Active Member

    Here I offer my very simple solution for a flawless and long lasting chain tensioner for single speed motor chains.

    As an axle, use 3/8" clevis or appropriate metal stud that will secure a 2" fender washer.

    In the pics, I used the remnants of a 3/8" Grade 8 steel trailer security seal. Again, a good hardware store will sell a 3/8' clevis that is more than strong enough for the job. You will need to grind flat spots on opposite sides to get it to slide neatly an tightly through the kit chain tensioner upright. That thing is very strong and will do just fine provided it is tightened down correctly. Use blue locktite for insurance. The genius of my design is that the entire thing is held by friction so the nuts and bolts that hold the upright are the only place for nuts and bolts.

    You'll need a hole in your axle for a 1/8' cotter pin, and that hole will be placed about 1/4" outside of the upright, once all the parts are fitted. I use a Grade 8 pin that I found somewhere. If you use a solid stud, drill using a 9/64" bit.

    It's hard to find 2" fender washers that have 3/8" holes. If you use a clevis, you will likely have to use a 1 1/2" washer with a proper 3/8" hole to secure the 2" washer on the end.

    Use 2 hard nylon washer/spacers (size: 3/8" hole, 3/8" width, 1" diameter) as the chain roller surface. The chain will quickly eat into the washers and find a solid equilibrium. It will take a very long time for the chain to eat all the way through to the metal axle.

    Use a few washers on the outside to pull the entire thing together. Get it as tight as possible. I had to grind down the leading part of the cotter pin to get it started into the hole and past the washers. There will be a bit of play but if the pressure is right, there's jsut nowhere for the chain tensioner to go.

    I've added pics here. One shows a kind of real life schematic style with all the pieces in proper order. Another shows the parts of the tensioner unit i. e. the part that holds the underside of the chain up. (You'll need just couple of washers outside to set the tightness. The other pic shows how the thing will look in service, with my hand holding it all together.

    I'll add a finished pic of this unit on the bike tomorrow.

    I hope this helps someone.


    Attached Files:

    CrazyDan likes this.

  2. Timbone

    Timbone Active Member

    Here's a pic of the new tensioner in service:

    Attached Files:

  3. JunkyardDog

    JunkyardDog Active Member

    Better than the stock roller, but in my experience it is the clamp on mounting bracket that fails. I even considered the possibility of welding on a stock bracket, but every one I've seen is made of really thin, cheap, easy to bend metal.
  4. Timbone

    Timbone Active Member

    I'd advise against welding because the chain/ tensioner interface is a static thing. You need to make adjustments from time to time. Not often, but every now and again.

    Fasten that thing tight! I am using a kit bracket and it is very strong. It's going to take a lot to bend it! Clamp that thing down as tight as possible! I use 5/16-18 Grade 8 bolts torqued up big time. Some blue loctite can only help.

    Your bracket is too weak? The metal bends??? Beef it up! Get some thick metal and use it to thicken the weak points. Either weld it together or be clever and bolt it on. The tensioner should not be a persistent problem.

    There are many ways to skin this cat.