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Engine Mount Spools

Fittings used for hanging an engine mount

By Dan Yager, for Experimenter, EAA 1041077

When building components for an experimental aircraft, part of the joy and pleasure comes from discovering a new or unique way to complete the task. With the use of the Internet, it’s pretty easy to find documentation concerning what you might be building, but the methods discovered may be a little too heavy or too light for what you might be trying to accomplish. In this case, Dan Yager found a construction method that was more than what he required,  so  he modified the system to be a little less robust yet still function for his needs.

Finished weld

I have a copy of William Wynne’s Corvair Conversion Manual and I attended Corvair College #14 in 2009. Since then I’ve been teaching myself how to TIG (tungsten-inert-gas) weld. My goal is to design and fabricate the mount for the Corvair engine that I will eventually install in my Quickie Q-200 project. One of the first steps to creating the motor mount is to weld together the bed mount and the various “spools” used for attaching the mount to the firewall and for attaching the engine to the mount.

My first thought was to simply weld a bolt to my welding table and hold all of the pieces down with a wing nut of the appropriate size. However, after trying to weld the first spool, it was clear that doing this on an immovable table wasn’t really the way to go.

Old system

Turning the piece to tack and finish weld the 360-degree seam is cumbersome at best. It quickly became obvious that a jig would have to be made!

I did a quick Internet search and found the following picture on Mark Langford’s web site. It shows the motorized spool welding jig that William Wynne employs.


William Wynne at his rotating welding jig used specifically for creating spools.
The spool consists of a flat washer and a short piece of 4130 chromoly tubing.
A completed weld. The blue tape shows the welder where to start and stop his weld.
The finished spools, some of which have been glass-beaded.

I’m not planning to go into production, so this level of complexity didn’t seem appropriate for what I was trying to do. However, it illustrates the need to be able to turn the piece while you’re welding. This got me thinking that perhaps I could make a similar jig that I could turn manually.

Raw materials
Raw materials

The solution was actually quite simple. When I was out at the local scrap yard looking for steel to build my welding table, I ran across a few end pieces of round stock that had clearly come out of a large lathe. The piece shown below is about 2.5 inches in diameter and about 3 inches tall. My plan was to take a bolt similar to the one I welded to the bench, and weld it to the approximate center of the bar stock instead.


So, I cut the head of the bolt off with a chop saw.


Then simply TIG welded the two pieces together. I ground the weld bead off a bit with a bench grinder to ensure the 4130 tube would seat properly on the bar stock. I checked the bolt was perpendicular to the bar stock with a carpenter’s square and made some “fine-tuning” adjustments with a couple of whacks of a ball peen hammer.


One thing I learned by welding the bolt to the table first was that you should weld on the cut end of the bolt. This preserves the threads on the other end and ensures that the wing nut will screw on with ease. If you look at the first photo, you’ll notice that I learned that lesson the hard way.


Once the bolt and bar stock are welded together, you can put the fender washer and 4130 steel tubing over the bolt and hold everything down with the wing nut.


Then you can make a few tack welds around the perimeter to ensure that the pieces don’t warp from the heat.


Next, continue welding around the seam until you’re happy with the results. If you have a good pair of welding gloves, you can turn the piece easily with your hand, and the bar stock is heavy enough to keep everything from tipping over.


In short order, you’ll have the 20 to 30 spools required to fabricate all of the motor mounts you’ll end up making during the destructive testing phase.

Spool Spool

I’m kidding. (I hope.)

Dan Yager is editor of the Quickie Builders Association newsletter.


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