Aluminum Overcast

Hello,

I have two RCV 120 SP's. One purchased at the Toledo show a few years ago (When Wildcat Fuels was the US distributor) and another Purchased from the KMP booth a year or two ago for one of their Spitfires. The older SP was to go into a Top Flight P40 which I was building. The engine sat in its box for a few years unused until this past year when my old trusty EZ zero (800 hours flying time with the same Saito 56) was lost in a mid air over our flying field. A friend had a World Models Zero that he gave me and since then (months) I have been working on this aircraft detailing just a plane old arf into something a bit more elaborate and decided to use the older SP in it. The engine ran fine on the bench and during break in but always had and continues to have a lot of vibration. More so than the newer SP which I have also broken in and is installed in my Spitfire and is nearing completion but not for this season. The older SP vibrates something terrible despite different props (currently I have a Solo Props 3 blade 16" installed). So much so that I seem to have developed slop in the high speed needle. The low speed just free spins without any travel along the threads and allows air to cause the engine to serge up and down. It is impossible to tune. I am confident that this is the problem because after thinking it was just that carb I unbolted the newer carb from the SP mounted in the Spitfire and installed it onto the older SP in the zero. All was fine.....for a few test runs on the bench anyway but soon it too developed the same issue. Supporting my theory is that I can see the black finish on the high speed needles worn off. I thought perhaps the engine was mis timed slightly so I reset that to no avail of the problem. Now I have two unusable carbs, Two unflown and disabled SP's and a warbird formation group (that I have flown with for 15 years) that isn't impressed with all the fuss in getting this engine going and the flying season is almost over here in Michigan. Can you help me resolve this issue Please?

weston uk rcv

Your vibration may be down to too much clearance in the gears. There should be a maximum of 1mm movement on the tip of an 18" propellor. The age of the motor would determine how you increase the gear mesh. If the crank carrier is square then thereare aluminium shims behind the crank carrier. If you need to increase the gear mesh then simply remove one of the shims and try again. If with all the shims removed there is still too much clearance then you need to machine the face of the crankcase. We strongly recommend that you return the motor for this procedure to be done, it must be done correctly.If it has a gear carrier which is rectangular with four slots the gear mesh is adjusted by swinging the plate clockwise to make the meshtighter. This should solve or help with your vibration problem as it is clatter on the gears which is giving you the vibration. On the older motors there was a different gear form which was not so good.

Arruda

Aluminum:
Beautiful planes!!!
I was wondering, what is this device you are using over the muffler header?
What is the purpose and who made it?
It seems that you’ve put the discharge on top of the plane. Is that correct?

Aluminum Overcast

RCV:
Well, I tried your suggestion of advancing the gear carrier clockwise. It did diminish the gear backlash a little but even at its furthers point spun clockwise I still have 2mm of travel at the tip of the 16" prop. My newer RCV has hardy any backlash on an 18" prop. The older vintage engine below has now ruined two carbs, two remote ignition wires and sheared a carb fuel nipple due to all this vibration. I hate to think what all this is doing to the rest of the models electronics and structure. You can see my attempt to field fix the high speed needle by adding a bit of silicone tubing. This is not a solution as the needle is wobbly only after only a run or two. Despite the fact that this engine sat in a box for a few years it was never used until this project and all these problems came with it right out of the box. Truly I do appreciate your prompt reply, however I am not at all pleased by having to deal with this situation, especially since this engine has only seen the sky for a first test flight in which the vibration actually sheared off the fuel carb nipple after three laps around the field and I had to dead stick my plane at the far end of the airfield. What do you suggest now?


Arruda:
Thank you for the compliments. I try. The header and down pipe you see on the Spit is something I have made myself. Although not completed yet it will be a scale exhaust complete with molded exhaust stacks. The material used is Aluminum for the header immediately exiting the engine and fiberglass cloth and slightly thinned out JB weld as the resin for the down pipe. The inside and out are coated with a high temp 1,2000 degree paint used for automotive headers to help insulate the resin and cloth further. It's an experiment of mine and it should have all been finished quite a while ago but, as you can see above...I have had other issues to deal with.

weston uk rcv

As you appreciate Weston UK had nothing to do with this design of motor but I will do my best tohelp you.Please send it back and I will do whatever is necessary to correct the fault. If you give me your email address I will forward the information you will require for making the return.

ktcanuck

Aluminum Overcast: Off topic but I notice you have used the O.S. exhaust flex pipe and been able to shorten it. I am using same on a 120 in a TopFlite Bonanza. It looks like you might have soldered or welded the pipe.

Could you detail what you did?

Many thanks

Keith

Aluminum Overcast

ktcanuck:

Yes, that is the O.S flex pipe. I believe that there are actually 2 lengths available 170 mm and 120 mm from them (tower Hobbies) including a cast 90 degree header that will fit the RCV 120 SP. Do a search on O.S FS-91 surpass accessories on the Tower Site, or, click here:
http://www3.towerhobbies.com/cgi-bin...0p?&I=OSMG2624

Both ends are threaded on these pipes (11X75 Same as the 120SP) and they come with a jam nut on both ends. The tube is made from a solid tub and, as such will hold pressure and gasses along its length. The end you see on my tube was made by me (last minute before a flying event in an attempt to get airborne) as I needed to exit the gasses out of the engine bay and also needed to use pressre from those gasses to pressurize the tank and prime it on first run. The nipple is made by me after the stock muffler and brass nipple simply sheared off along with the mufflers (2) due to the vibration loosening and then chewing up the threads on both mufflers from this engine and same parts from my newer engine in the Spit. I realize the 120SP does not have a lot of pressure it generates as the RPMs are not as high as other engines but, the bit it does help on fuel delivery to the carb in my set up. I threaded it and then Silver Soldered it to my exhaust stack, it won't vibrate or shear off now! I would like to move it up the tube as I know the pressure would only be greater there. Unfortunately, so would the heat as well so, Ill make a new pressure nipple which will be longer with cooling fins at the base of it to keep the silicone from burning off. I had that happen on the break in runs on the bench. And, when it did, it changed my high and low needle settings. Not so good if you are flying......