Build an Engine Test Stand
Or, How Pat Panzera Built His
Story and photos by Patrick Panzera, EAA 555743, firstname.lastname@example.org
EAA’s Experimenter e-newsletter Editor Pat Panzera running his test stand at the 2004 COPPERSTATE Regional Fly-In
Several of the candid head shots of Experimenter Editor Pat Panzera have shown him operating an engine on a test stand towed behind his pickup or van. A number of people have inquired about the construction of it, so this month’s How To will be about how Pat built his stand.
Right around the turn of the century (1999 to 2000, not 1899 to 1900), I was heavily involved in the development of a firewall-forward adaptation of a Corvair engine to a Quickie Q-2. The Corvair is an automobile built by the Chevrolet division of General Motors from 1960 to 1969 that used a horizontally opposed air-cooled six-cylinder gasoline engine. As such, it’s a really good fit for the 100-hp experimental aircraft engine niche.
The majority of the engine conversion work for the Quickie firewall forward was a pretty straightforward adaptation of the process outlined in William Wynne’s engine conversion manual, but there were some areas that I felt needed changing for my application. As far as I knew, I was the first to try this combination of engine and airframe, so I was on my own to pioneer these changes. The biggest difference between a Wynne conversion and the one I was attempting was my desire to keep the engine located as far aft as possible and to locate the accessories as far aft as possible, both of which I felt were necessary for weight and balance, not to mention keeping the longer six-cylinder engine inside the four-cylinder cowl.
Pat’s engine being adapted for a starter and alternator located at the rear of the engine
The Q-2 I was partners in at the time was built for a Volkswagen engine, which is at least 40 pounds lighter than the lightest Corvair conversion. Fortunately for me, there were other Corvair builders who (although not building a Q-2) also adhered to the same philosophy that the starter and alternator should be located at the rear of the engine. Several of us came together on an Internet e-mail group and gave each other support. Although Wynne was the first to adapt the starter to the rear of the engine and the first to test-fly this combination, he wasn’t happy with it and decided that it was best continue supporting the front starter only.
Sometimes I get a little carried away with my projects, wanting tooling and jigs to be as equally exceptional as the project itself, and the engine test stand was no exception. Although I could have easily (and far less expensively) cobbled together a suitable fixture from lumber, I felt the nagging appeal of owning something more durable with which I could use on future projects, Corvair or otherwise. So I decided to make it from welded steel.
My needs were simple but specific. It had to fit in the bed of my truck, between the wheel wells. I have a Mazda mini truck, so I didn’t have a full 48 inches to work with like one would have with a full-size pickup. The magic number for me was 39 inches. I also knew that I might be taking it on long trips; I wanted to be able to lower the engine to keep it behind the cab for streamlining. I also wanted to be able to operate it while standing on the ground behind the truck or standing on the tailgate, whichever I might prefer at the time, so I wanted the instrument panel to be easily repositionable.
Since these were the only parameters that really mattered – other than while the engine was in the “up” position, the prop needed to clear the bed of the truck – I went to the local metal fabrication shop and began digging through their remnants. I felt it would be prudent to design around easily obtainable (cheap) raw materials as opposed to arbitrarily designing something that required materials which had to be ordered or were otherwise costly.
So the first thing I needed was tube steel that could nest to create the sliding system for raising and lowering. I found that 2-1/2-inch tubing fit nicely inside 3-inch stock that had a 3/16-inch wall thickness. From there it was just a matter of eyeballing what looked like would be substantial enough to carry the loads.
The spacing of the two 1 x 3 cross members was defined by the engine mount I was planning to initially bolt to it. But at that same time, I knew future installations of other mounts would be as simple as perpendicularly bolting another pair of 1 x 3’s to the originals if the hole spacing is outside the range of the original design.
Once I had my material in hand and my design complete, I cut all the components. I have a friend who at that time was attending a CNC (computer-numeric-controlled) machining class at the local community college, and he volunteered the welding students to weld my parts into a useable creation. My friend was also converting an old horse trailer into a flatbed, so he offered to paint the stand at the same time he painted his trailer. He also offered to allow me to use his trailer so I wouldn’t have to drill mounting holes in my truck bed.
With the stand built and mounted to the trailer, I was able to mount my engine. I used a piece of 3/4-inch plywood skinned with a sheet of aluminum to represent the firewall. It was of course sandwiched between the 1 x 3 cross members and the engine mount, held in place with the through-bolts.
I had already designed and built my prototype engine mount, so I hung the engine and installed the remote oil cooler and oil filter, as well as the firewall pass-through bungs.
The plan was to get the engine running in time to allow me to bring it, on the stand, to show at the then-upcoming Quickie and Dragonfly gathering in Laughlin, Nevada, about 400 miles from where I live. But due to technical issues with the engine itself, I had to scrub the running of the engine and just bring it as a static display.
The engine was installed on the stand in the "up" position with help from a friend. When it came time to leave on the 400-mile trip, no one was around to help me lower the engine to the streamlined position, so I decided to just drive with it up. I have about 20 miles of country road to drive to get to the interstate, and even floored, my little truck would barely indicate 50 mph. It was looking like it was going to be a long, stressful trip.
Just before I got to the interstate, I found a tire store with some helping hands that was just opening for business; it was still early in the morning. I pulled in and asked if I could get some help lowering the engine into place. Long story short, with it in the lower position, I had no problem doing well in excess of the speed limit. The aerodynamic drag was gone. Even though the streamlining concern was for when the stand was in the bed of my truck when the engine would be higher than the cab, lowering it on the trailer paid off, too.
Although I needed to shelve the Quickie project for a while, I still had to finish the engine stand for another engine I wanted to operate. This engine project was to create a Dragonfly firewall forward. So I removed the Q-2 engine, mount, and firewall and installed the Dragonfly engine, mount, and firewall.
Note the bends along the top and bottom edges. There’s a 1-1/2-inch lip bent at 90 degrees to give the panel rigidity. Just out of the shot to the top is another set of bolt holes for relocating the panel higher. The wires have some extra length to them and are coiled so they stay neat when the panel is in either location.
I wanted to give the instrument panel an industrial look, so I chose to use polished aluminum diamond plate. I had the piece custom-cut and bent to my specification by the same shop that sold me the remnants. The 90-degree bends at the top and the bottom are for rigidity, allowing for a lightweight installation. Although I really wasn’t concerned with the weight of the structure, I felt it best to keep the weight down on nonstructural elements.
With the panel in place, I populated it with a few rudimentary automobile gauges, and eventually, a manifold pressure gauge I got off eBay. A pair of push-pull cables (for fuel and mixture), few fuses, switches, coils and ballast resistors, along with a fuel system (including pump and pressure gauge) and a 12-volt battery, and the Dragonfly Corvair engine came to life.
First public running of the engine stand at the 2003 Dragonfly/Quickie fly-in at Laughlin, Nevada.
Since then, I’ve probably logged 20,000 road miles or more taking the engine “dog and pony show” to various experimental aviation gatherings around California, Nevada, and Arizona, from Golden West to COPPERSTATE, including EAA Chapter One’s Open House and CONTACT! Magazine’s Alternative Engine Round-Up. Although I didn’t know it was the direction I was headed in when I built it, this engine stand is responsible for exposing hundreds (if not thousands) of individuals to the viability of using an automobile engine in experimental aircraft.
We also have a little fun with it from time to time.
The engine always draws a crowd whenever I fire it up. It also draws a crowd at gas stations, too, when I’m on the road. I usually must allow an extra 20 minutes to each fuel stop to give an impromptu “engine forum.”