GMS Engine parts?
02-24-2019, 02:38 PM
#1
GMS Engine parts?
I have a GMS2000 .32 engine with broken throttle linkage. I'm not sure if throttle linkage is the correct term -- it is the part that connects the throttle pushrod to the carb rotor. It affixes with a set screw and has clearance in the hollow center for the low speed needle adjustment screw. It seems as if it were made of metallic colored soft cheese, as it broke with little effort on my part. I've JB welded it for now but would never trust it to hold together with engine vibration, potentially leaving the model stuck at the last throttle commanded if it were to break again. I have the engine shoe-horned into a vintage 1980's Bi-Fly 25 that is a favorite survivor plane, so want to get rid of the JB Weld fix and address it properly before flying.
Does anyone know of a source for GSM engine parts? Anyone with an old parts engine that would be willing to sell or part out? Any known mechanically compatible carb assemblies from other manufacturer that could drop in?
Does anyone know of a source for GSM engine parts? Anyone with an old parts engine that would be willing to sell or part out? Any known mechanically compatible carb assemblies from other manufacturer that could drop in?
02-24-2019, 05:01 PM
#2
I’m sure the same part from another manufacturer for a similar sized engine should fit; if not directly, with little modification. OS and Thunder Tiger used the same type of throttle arm mounting, so I’m sure you can source something that will work.
02-24-2019, 09:51 PM
#3
I have the same engine, so I looked at it to see how it was built. Sorry Quick Sport but it is retained on the barrel by two "upset" marks. My suggestion would be silver solder. Don't use regular solder, or "soft silver". If you can't do it yourself, try to find a modeler who can do it for you. If that doesn't work, try to find a jeweler who will repair it.I suspect it broke at one of the two bends, so when you repair it, make a fillet of silver solder in the bend. It's possible that a capable fabricator (aka. modeler) could adapt an arm from another manufacturer, but I think by the time you removed the original piece from the barrel, and then tried to get the replacement back on the barrel you will have exhausted a lot of energy, and flowery vocabulary! Good luck, and let us know if you have any luck.
02-25-2019, 02:46 AM
#4
The throttle arm itself is retained on a small collar with a setscrew - the throttle arm is crimped to the collar. The collar is retained to the carb barrel via a setscrew. OS makes carbs the same way. I have a GMS .47 and that’s exactly how the .47 carb is setup as well. Unless the .32 is a weirdly different animal, it should easily be repairable using a throttle arm from another carb.
02-25-2019, 10:50 AM
#5
Quick Sport you are correct. The throttle arm is "staked" to a collar in 4 places, and the collar is retained to the barrel with a set screw. That was more detail then I wanted to get into when I posted earlier. I still think the simplest solution is to silver solder the broken arm. Parts for all of our glow engines are getting harder to find, and you might find a similar part for another brand engine, only to find that it's not usable. The depth, or thickness of the collar could be a miss match? The hole in the replacement arm could be too large? That doesn't mean it's not another option, particularly if you have a used donor part available. I've had great success fixing broken carburetor arms by silver soldering them, so that's why I made that recommendation.
02-25-2019, 04:00 PM
#6
I have had a hard time sourcing silver solder around my neck of the woods. The closest I could find was the plumbing grade stuff that has barely any silver in it. So anytime I’ve been suggested to silver solder anything, I find other means. Of course this doesn’t mean it cannot be found, but the cost of it for me is prohibitive. Parts engines are easily obtained on the forums or eBay for pennies on the dollar, so I will often suggest that route first. I’ll bet parts for a Thunder Tiger or OS carb will fit with little or no modification. But I say do what works with what you have available.
02-25-2019, 10:22 PM
#7
I did some checking. The Thunder Tiger Pro 40/46 carburetor collar won't work as a bolt on replacement. The hole is larger then the hole in the GMS collar. It could probably be sleeved? There may be some other Thunder Tiger collar that might work?
02-26-2019, 04:41 AM
#8
I haven't seen any similarly designed parts on O.S. or Thundertiger drawings for .25 to .40 sized engines. They all seem to retain the control arm via axial blind nut or machine screw through the arm tapped into the center of the rotor. The blind nut concept is sort of close, but diameter is way smaller than the GMS implementation and lacks the set screw.
Upon close inspection, the lever arm ring was in fact staked to the sleeve in four places. The metal didn't break like I thought, rather the poor staking job just let loose. I'm thinking I'll try removing the JB weld, re-staking it and re-brazing with some silver solder as suggested.
Upon close inspection, the lever arm ring was in fact staked to the sleeve in four places. The metal didn't break like I thought, rather the poor staking job just let loose. I'm thinking I'll try removing the JB weld, re-staking it and re-brazing with some silver solder as suggested.
