Building an engine test stand
Tutorials > Building an engine test stand
Until 2016, when I built an airplane I installed the engine without running it first. Since I am in the habit of buying secondhand engines it occurred to me early in 2017 that it was high time I had an engine test stand. Many large ones are available but with limited storage space and (likely) limited usage I wanted something smaller.
While doing some research I came across a Fly RC magazine article from 2010 titled Build an Engine Test Stand and I knew it was the one for me. Firstly, it uses a Black and Decker Workmate as a base, and I already have one. Secondly, it uses a modular plate system which could mean a plate for each engine I test. I followed the design for the most part, with a couple of small changes.
Here are the plans:
Tools and Materials
My stand is made from 3/4" plywood (with one exception) and is assembled with glue, screws and 1/4-20 hardware and reinforced with 1/4" dowels. Required tools are a drill and bits, screwdrivers, hammer or mallet, measuring tape, pencil, clamps, and a saw.
I have some woodworking skill but I am no cabinetmaker and I made plenty of mistakes (and some changes). See the comments in italics and the Summary section below.
I happened to have a piece of 3/4" plywood that was big enough for all the pieces. I decided to make three of the modular mounting plates. I don't know why the plans specify 6" x 8" mounting plates when the firewall is 6" x 9". Future plates will be 6" x 9".
We have a decent wood shop, so I used table, mitre and band saws to cut the pieces. It could be done with a circular saw, a jigsaw (with a steady hand), or a hand saw (with patience and a VERY steady hand).
Here are the pieces. I was so eager to start I forgot to take a picture before I started assembly - here you see the firewall glued to the base with the forward cleat and clamped to cure with the help of a couple of the mounting plates.
I pre-drilled the mounting plates for their attachment to the firewall. I put the lower holes too close to the bottom of the plates because I forgot to take the height of the base into account, so I had to plug them and re-drill them higher up. Before doing that I clamped a mounting plate to the firewall and drilled the top holes.
Once the new holes were drilled through the mounting plates I marked and drilled them through the firewall, then attached the plate with 1/4-20 bolts, 1/4" fender washers and blind nuts.
I decided I wanted spacers between the mounting plate and firewall to allow for routing of lines and wiring, and to provide space for hardware behind. I cut some to length from a 1" dowel and drilled them to 1/4".
The next job was to create slots for the braces. I should have done this before I started putting it together. I did what I could on the band saw (mostly straight cuts)...
... then switched to a hand saw for the angled cuts.
Eventually I had the braces fitting the way I wanted, so they were glued and weighted to cure.
I trust the glue I use (Lee Valley Cabinetmaker's Glue 2002 GF) but I wanted the extra security of dowels, so I marked the braces for drilling.
When drilling through most wood (plywood included) I like to use brad point bits. To prevent tear-out in plywood I run the drill in reverse at low speed so the spurs on the bit can scribe the top layer cleanly.
2" lengths of 1/4" dowel were used. I like to taper the dowels for easy entry, and sand a flat spot on opposite edges to allow the glue to squeeze up. After the dowels were glued in place, I cut them flush. Then I trimmed off the ends of the braces. With the table saw. VERY carefully. More cuts that would have been better made before assembly.
Next, the spacer, which is attached to the underside of the base and is clamped in the Workmate to hold the stand in place. I had to make mine a little thicker than 3/4" because of the thickness of my Workmate table, so I cut some 1/4" plywood to shape and glued it to the spacer I'd already cut.
Spacer glued and weighted to cure.
And here's the stand clamped in the Workmate for the first time.
Now for the cleats, which mount perpendicular to the spacer and act as a backup restraint. Cut 6" long as specified in the plan they didn't fit the widest opening of my Workmate, so I trimmed off 1/4".
Now screwed to the bottom of the spacer. Those are #10 2-1/2" screws that fasten the cleats all the way through the spacer and into the base.
Clamped in the Workmate again.
I picked up some 1/4-20 socket head cap screws to replace the Robertson head bolts. They use a 3/16" hex bit.
Stand clamped, mounting plate bolted.
Last step - put some filler in the low spots and glue the standoffs to the firewall.
I figure the mounting plates are going to get the bulk of the splatter, so those get coated with Helmsman Spare Urethane.
Three coats should do it. Two coats so far (then I have to do the back).
I like this grey brush-on rust coat too, so the rest of the engine stand gets that.