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Control Mount Repair By Barnstrorm Cycles

 

Greg Doliber's Shovelhead suffered some damage when a four wheeled death machine inserted itself into his direction of travel. Fortunately for everyone, while not being an ideal scenario, no one died or was injured in any major fashion, and the overall damage to the bike was limited to what’s covered in this write up, as well as the front end, foot controls and some smaller components. On the road to recovery, our first order of business was to confirm that the frame was still straight, which we did in the jig. It passed with flying colors, and upon further inspection, we determined that the only real damage to the frame was the front right foot control mount. It had been “rolled and twisted” upwards and out, when the bike went down and the controls caught the ground. The force of the controls pulling on the mount also stretched out the threads.

 

 

The goal was to remedy the mount so that it was again strong, functional, and looked as if nothing had ever happened. The first thing to do was to try and get the mount back to being as “flat” as possible. To do this, I simply placed the frame square in the shop press, added some downward pressure a little at a time, with periodic checking, until I felt I had brought the mount back pretty close to where it had originally been. I wasn’t concerned with getting it perfect at this point, because the next few operations would finish the job.

 

 

Moving on from the press, I spent some time securing the frame in our Knee Mill. This took a little finessing, but I did finally get it into a sturdy enough position for what I needed to do. I used the opposite side foot control mount and a few other frame locations to square off of, and since the critical tolerance for square-ness of the foot control mount I was fixing was in all reality pretty low (meaning that as long as the finished mount was “prettygoddamnclose” to looking square in the end everything was going to be A-OK) I wasn’t stressing over thousandths. In fact the most important part of this job, I would argue, is actually the thread repair. Without good threads, bolting controls to the frame would not be possible and/or safe.   

 

 

After taking a light skim pass off the mount face to clean up the burrs around the tapped holes. I went about centering the mill on each hole and countersinking each one in order to remove as much of the old holes as I could.

 

 

Since I didn’t want to disturb the location of the frame in the machine, I left the frame in place for welding. I just lowered the table down for access, and then rolled the TIG welder over. After cleaning the entire mount, I filled in the now larger holes with weld using regular mild steel wire, and also ran a few “build-up” passes on the face of the mount to add a little thickness back.  

 

 

You can see the end result of the welding operation here. The mount basically has no holes left in it (aside from the remnants of the original holes on the backside of the mount…) and is now ready to be faced, drilled and tapped with new holes.

 

 

After facing the mount back to a solid, flat surface, leaving the milling lines somewhat pronounced in an attempt to match the factory machined surfaces on the frame, I laid out the location of both new holes the old fashioned way.

 

 

I performed each operation for each hole in sequence; center drill, drill, tap, chamfer- completing one hole entirely before moving onto the second. I took this approach as a result of the way the frame had fit into the mill, which put the centerline of the new holes out-of-square to either machine axis. Since my machine is not CNC (nor am I), this method, while a tad slow due to repeated tool changes, was more accurate as I wasn’t trying to find zero over and over.

 

 

After a bit more cleanup work, the repaired mount looked good as new. And with all-new, all metal threads, there were no longer any safety or fitment issues to worry about.

 

 

For the less outfitted shop, this method could still be carefully applied with a drill press, angle grinder, files and a bit more time and patience. Again, I would place your focus on getting the threads properly fixed and making the mounting surface flat. As always, there are probably a myriad of other ways to do this same job. For example, you could cut off the damaged mount completely and weld-on a replacement. For this job, I simply wanted to remove as much evidence of anything ever happening, and decided this was the best way to do that.

 

Please feel free to share your thoughts, personal approaches and experiences. I would love to know how other people have dealt with these types of issues, and someone else may benefit from your knowledge base too!  

 

Thanks,

Jake

Barnstorm Cycles


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Commented on 7-14-2014 At 12:00 pm
 

great write up

Commented on 7-14-2014 At 12:13 pm
 

I love the tech articles. just looking at bikes is sick, but learning how to build and repair them is really rad too, and these might come in handy down the road.

Commented on 7-14-2014 At 12:16 pm
 

Looks good. Only thing is I personally would have chamfered the hole before tapping just to avoid pushing a burr into the threads.

Commented on 7-15-2014 At 05:33 am
 

nice write up!!! three words... MORE METAL SHOP \m/.

now, i'm trying to put a fuel gauge on my bike, is an old rebel and don´t have one, it will be great some write about this....

Commented on 7-16-2014 At 08:02 pm
 

Great write-up. Thanks for taking the time to shoot photos for every step.

Commented on 7-21-2014 At 12:00 am
 

Great tech article. More please! Especially about repair, refurbish & reusing.

Thanks

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