Bolted on Tabs and Welded on Tabs
1). Bolted on Tabs
At the bottom rear of the swingarm angle iron tabs can be bolted on.
This requires fabricating the angle tabs, and removing the swingarm to drill two 8mm holes on the bottom rear of the swingarm behind the axle. The holes behind the axle should not affect the structural strength of the swingarm. Also, the swingarm is real easy to remove. This does not interfere with chain adjuster at all and the chain adjuster can still be pulled out of the swingarm.
Making the Tabs. All my cuts were made with a electric 4 ½” angle grinder with ⅛” cutoff wheel. Mount the angle iron in a vise, or vise grip pliers clamped to something solid. wear gloves, the metal gets hot, it has sharp edges after cutting, and sometimes the grinder will try to jump out of your hands.
I cut two, 1 ¼ inch wide pieces, from 3/16 inch thick x 1 ¼ inch x 1 ¼ inch steel angle iron to make the tabs.
You need a 6” rule and a metal scribe to mark the steel for cutting and drilling. First layout the face, It will only be 1” wide. later you will cut ¼” off the front edge of the face. Scribe a line from bottom to top of the face 1” from rear edge, and continue on the top edge 5/16”. When you cut this ¼” off the front edge the face will be 1” wide. On the second piece of angle iron the line will be on the opposite side, or its front edge
Now layout the holes to be drilled. On the face mark the center of the spool mounting bolt hole. It’s ⅞ inch down from top and ½ inch from rear edge. My spool mounting bolts were 8mm so I drilled a 5/16 inch hole. Most spool bolts are either 6-8-or 10mm.
Next layout the two mounting holes on top of the angle iron. They are centered ⅝” from the outside edge, and 5/16” from the front and rear edge.
I should point out that 5/16 inch and 8mm are the same. Next center punch all the holes, the bigger the hammer the better. A bigger dimple helps prevent the drill from wandering. I used a harbour freight step drill bit mounted in a cheap chinese drill press to drill the holes.
There is ½ inch of room inside the swingarm for the nuts and bolts to come through. They only take up ⅜ inch. I used M8mm x 20mm length socket head cap bolts, lock washers, and
nuts to attach them. A 16mm length can also be used. These can be tightened from the bottom with an allen wrench.
There is not a lot of room inside the swingarm for a wrench to move. You can use it to hold the nut while turning the bolt with an allen wrench. After drilling the mounting holes in the angle iron I used it for a drilling guide for drilling the swingarm holes. Here you need a 5/16” drill bit instead of the step drill bit, as it will just wander around. I clamped a piece of metal for a straightedge to the outside edge of the swingarm and clamped the tab to it so it would be perfectly straight when drilling the holes. Use blue painters tape on side of swingarm if you don’t want any scratches. Because of the clamp on the tab you can only drill one hole at a time. Drill one hole put a bolt and nut in to hold the tab in place. Make sure the tab didn’t move when tightening the bolt. Check it again before drilling the second hole.
Swingarm is upside down
The rusty bolt is the same diameter as inside spool diameter. The metal piece on the outside of the swingarm curves under the swingarm. As the axle is moved back for chain stretch the angle iron is notched to allow clearance for this
The black coating on the steel is mill scale and it needs to be removed before painting.
A one foot piece of angle iron is available from McMaster-Carr
for under $5 plus tax and shipping. I paid around $12. The part #9017K15
is what I ordered.
2). Welded on Tabs
If you can weld, or if you have a friend that can weld the tabs on for you, This is what you need. Tabs made out of 1” x 1” x ¼” thick steel flat bar.
You can buy tabs on ebay cheaper than making them yourself. (I wish I had know this before making 3 sets). Here’s a link to the page Weld Tabs 1 4" Steel Pack of 10 | eBay
they are 1 1/4 tall and 1/4" can be cut off. The hole size is not listed but you can ask and he’ll probably make it any size you want. Most spool bolts are either 6-8-or 10mm.
I removed the swingarm to weld them on.
I clamped a piece of metal for a straightedge to the outside edge of the swingarm and clamped the tab to it so it would be perfectly straight when welded.
All the bikes I looked at had the spools in front of the axle. Measured with the chain adjuster removed mine are 3 inches from the rear of the swingarm to the rear edge of the tab. Any shorter and you can’t move the axle all the way forward.
pictures coming soon