I started to build gas airplanes again and noticed some of the motors are a bit rough at the start before break-in, as the building season is approaching new projects are in the works again. I thought I would break in my motor on a simple stand but then started doing some research on aspects of breaking in aircraft motors. The two problems with most test stands is that they are rigid, the other is a lack of cooling. Bolting up a motor to a solid mount can actually destroy the motor when vibrations or harmonics occur. While some motor manufacturers say its best just to fly the motor, others do not. It is nice to have the option to do this out of the airframe to sort out or even get used to using the motor. I noticed
my DLE 30 was quite rough in the beginning so I decided to make a stand that could absorb the damaging harmonics and simulate the airframe by allowing moment and absorption of those damaging vibrations. additionally, I was not putting extra wear and tear on the airframe or risking a poor running engine on maiden flights.In short, I needed something to simulate the airplanes ability to rock and roll on the rubber tires to absorb these vibrations so that led to the creation of the Shaker...Vibration Absorbing Engine Test Stand. Its a mouthful so I just call it the Shaker...I have run 30cc up to 200cc motors with ease and on the larger motors with (inline 4's) there is an additional problem I noticed even with full-size aircraft- the rear cylinders run much warmer than the fronts do, so I made a bolt on cooling should that catches the prop wash and not only cools the motor but it also redirects the airflow directly over the rear cylinders to avoid overheating during break-ins. An alternate method is a box fan underneath the motor when it's on the stand, but the cooling should do it job. Which makes you think more about your cowl and possible baffles that may be needed with these motors.
The final item to think about was once you drill out the plate for the motor, what about other motors with different bolt patterns? The solution was swap-able motor plates. This makes the motor mount area over 2" thick of high-grade Baltic birch plywood. Very Stout with only 4 bolts to remove everything- motor and shroud. Ultra high-grade alu rails mount the stand to just about any surface. I wanted overkill- I think I got it. :)
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Last edited by Jim T. Graham; 09-21-2018 at 01:22 PM..
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Nice!
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Australia, NSW, Bellingen
Joined Aug 2016
53 Posts
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Bridged?
I may have missed something in my quick look at this, however, it seems to me that the springs will be effectively bridged by (what appears to be) a single through bolt in each one.
Normal "Lord" mounts, like common automotive engine mounts, have a separate, isolated bolt each end of the rubber (or in this case, the spring.) If my assumption here is correct, this nice little stand can be very easily modified to take isolated mounts. |
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Still putting mine together! Very, very high quality of wood, and cuts. Currently using thinned-out epoxy as a sealant before assembly, then i'll do another epoxy coat after. Going to break in a 3W 112B4 on the stand..... I'll report back with photos and a short review !
GM |
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very nice,
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United States, NJ, North Arlington
Joined Aug 2010
12 Posts
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One has to ask !! What size spinner are you swinging wih this engine ? Lol that is a massive nose piece ....
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