Over in our beloved helicopter newsgroup, (rec.models.rc.helicopter) we’ve had many discussions about the best (and worst) way to tune engines. Everything from throwing your pride and joy far into the air and hoping the engine won’t quit, while you watch and listen for signs of distress, through using infra red Ray-Gun type temperature sensors to ensure the mixture settings don’t let the engine overheat, up to using some form of test stand.
The test stand is my preferred method for a couple of reasons. One is that the stand places the helicopter high above the ground (and us) allowing us to operate from beneath the heli while we make adjustments.
This means we don’t have to take off, land, adjust and go through all the flight thing again to check the adjustment. Another reason is that ONLY with a test stand is it possible to alter the length of a tuned pipe while the heli is running at full throttle with a full load on the engine AND change mixture settings at the same time. Mixture settings can be changed and checked at the revs where there’s a problem/concern and if you go too lean, it takes only an instant to richen back up again. None of this is possible if the heli is flying.
The stand we use was made by John (one of our little group) from “Uni-Strut” steel girders and stands over 6 feet high.
The bottom of the stand is a large rectangle of steel with a central “pillar” which has the heli attachment point at the top. This puts the blades around 8 feet high, leaving plenty of room to move around underneath.
It sounds quite dangerous, but after 10 years of using it without a single injury (and we HAVE had helicopter failures while they’ve been on the stand) it’s not proven to be a major concern.
One 60 sized heli threw a blade when the bolt snapped, and this lead to some serious damage to the machine, but none to the stand or the “operator”. The workshop/shed in Johns yard suffered a blade stabbing though, but it survived and lives on. The shed that is, not the blade, we threw that awayJ
It seems that the safest place to be is directly underneath the heli as even when the 60 self destructed, there wasn’t a mark on the stand.
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