Were these distributed through Brodak? That is ringing a bell a bit. I think they came out of England?? I do not think they saw wide spread use. One thing about any engine you may be considering, just look through contest results and see if you can find the engine in question. If any engine showed any promise or really delivered on performance, you can bet that some one would be using them. Search through the forum here, and if anyone was using them in the last 20 years, you should find mention of it!
  Type at you later,
   Dan McEntee

I've had one apart. Not sure what info you are looking for?

The one in the picture had a spun rod bearing. It also had a cracked rod. No way to tell which happened first. So, of course the backplate was chewed up and a metal chunk or two went up thru the bore and gouged the piston in a couple of places. Since we had no prior history on the engine, or how it was run, it could have been from excessively lean running and overheating with a lack of oil, or....

I don't have any background on this engine. So it may have been abused, and damage is not the result of poor quality. So I'm not faulting the manufacturer. It was purchased by a friend who wanted me to test it. It had a couple of scratches on the piston that I didn't like, and it didn't feel as loose as I thought it should. It didn't feel too bad, actually, so I was pretty disappointed when I popped off the backplate to inspect the insides.

One scenario is that the rod cracked first, and then the bearing spun. The oil holes in the bearing and the rod are rotated. And then, presumably as the engine kept running, perhaps screaming lean (or not), the bearing walked out of the rod on the cracked side towards the backplate. The backplate was really chewed, but it is surprising how much end clearance there must have been to start with. As far as why the rod might have cracked first, it might have been from a shaft run, or....? Heat may have been a factor, as the strength of aluminum falls off appreciable with temperature. I agree that this the kind of thing you see in R/C car engines, likely due to extreme rpm sometimes under no-load conditions, heat from a cowled application, and a really miniscule oil package in the fuel. I've seen the rod in a car engine split the length right up the centerline, which is an interesting failure mode.

I seem to have acquired a .53, guess I won't bother building anything special for it, might throw it in the mule and see ( Doodlebug)

I tried an Aviastar 46 about a decade ago. Was pretty much useless for stunt flying. The stock venturi was too small and restricted it from making useful power. I opened it up and it would start a flight at a nice setting but would run away and you’d be hanging on to the handle with two hands until it ran out of fuel.

Eventually I made it useful by running a finer pitched prop. But it was not ideal. Also had an RC version which was also useless. Terrible carb.

Steve,

The Aviastar .61 rod was definitely machined from plate or bar. The deburring was crude, but I doubt that a swiveling tool was used based on the appearance of the markings. That said, you'd have to really work at it to get the inconsistencies on the different edges.... 

Wrought aluminum is close enough to isotropic that you shouldn't have to worry about grain orientation. If you are trying to cut the factor of safety that close...well, good luck to you. This rod had some other problem, either in construction or operational abuse. The latter wouldn't surprise me.

Dave

Steve,

The place I often saw a directional grain callout was on formed sheet products. You could bend a slightly tighter bend radius across the rolled direction (grain) of the sheet. We tried not to go below the normal minimum bend radius when designing parts because on some parts with the processing involved it became difficult to be sure if it was oriented properly. All were aerospace parts and as far as I was concerned, high rel.  No need to embed field failures into the equipment. Once you head off into composites directionality is absolutely everything. And, the latest "craze" in printed parts has that issue and many more.

I was one of the "office nitwits" which you speak of. The QA guy could be our best friend when the pressure on the fab shop was ratcheted up too high. MIL-T-FD, buddy....

Dave