Arruda

Burgerup, where did you place the aluminum back plate that comes with the engine to fix it in the firewall?

bugerdup

Arruba,
Due to the construction of the Top-Flite kit you are unable to mount the backing plate without cutting it in half, so I reinforced the back of the fire wall with two pieces of 1/8'' ply epoxied to the back of the fire wall. I have since installed the vibration isolator and mounted the backing plate to that. I also used larger hardware.

Arruda

Thank you Burgerdup.
I have a 90 sp and it took 2,5 galons to get a consistent idle and transition.
The vibrations will never go away, but it is possible to live with it.
I just reinforce the firewall and the junction between the wing and fuselage.

ktcanuck

I have to ask, and forgive me if there is an obvious answer that I am missing, since here we have a fairly broad spectrum of users having the same problem with this engine but I have yet to see any words of wisdom or comment from RCV or their agents. Some level of comment from the designer might be helpful to avoid or mitigate the problems being encountered. The engine documentation talks to the expectation of higher torque due to the 2 to 1 gearing but there is no reason to expect a level of vibration that shakes the bejabus (sp.?) out of our new babies.

Anyone?

gasayers

Well I've found part of my problem. After reading that the 18" prop should have no more than 1mm play at the tips I removed the gasket.
Now the gears are "bottoming out". Trouble is if I get the gaskets to stop the gears bottoming out then I get more than 1mm play on the prop.
Conundrum!

barry wetherell

Gassayer, which is the better option???
A.a Barry

barry wetherell

yea me again, I,m just about to "unload 2 x sp 90's , for all the above the reasons, anything you think might improve, would be greatly appreciated, Gasayer, as for the manufacture, one would think that some message would have got through, it is strange a forum as big as RCU, is, they haven't added any comment, or do they "let sleeping dogs lie"
A.a Barry

gasayers

Sorry about that Barry. It was never my intension to put anyone off these motors. As stated, mine started, ran, idled, transitioned, developed power as good as any other motor used. Really wanted to get mine going and this is supposed to be the manufacturers, (or representative) forum.

Also remember the90 does not appear to have the issue to anywhere near the same degree and the http://manuals.hobbico.com/gpm/gpmg2000-manual-v1_2.pdf should remove any remaining issues easily.

You have to assume they've sold literally hundreds if not thousands of these motors and presumable a lot are being used quite successfully.
I will have another go with mine as I refuse to be beat and in fairness I have not contacted RCV directly which would be the logical thing to do.
Now that I've repowered my spitfire electrically the urgency has gone out of the rcv so it could be awhile before I sort it out. But rest assured it'll be getting more attention yet. It'll just go into something different.

There is an sp running very regularly at our club and it’s awesome.
Cheers
Glen

The second diagram is the only useable option as the gears bottoming out will beggar the bearings very quickly if not already ruined.

andi3142001

Hi,

one question to the engine mount system from great planes: If I understand the drawing right the screws are surrounded by rubber grommets. The grommets are squeezed together when the screws are tightened.
Is that right?

Cheers
Andi

bugerdup

Yeah, It comes with 1/4 20 bolts and blind nuts and washers. the rubber is very hard and makes it feel very solid when tightened.

andi3142001

Well thanks[8D] I see you can even use a rod for throttle, and do not need a bowden cable. So this mounting system keeps things rigid and absorbs vibration energy.
Seems perfect!

Cheers
Andi

andi3142001

Did anybody try those http://www.blindnieten.at/HTML/en/Pr.../neoprene.html ?

Arruda

Hi Bugerdup,

I loved your muffler.

Did you make it yourself or it is available somewhere?

Leonardo

bugerdup

I bought it from Keleocreations.com It was redesigned and this is it. very high quality and outstanding service. $105.00. check him out. the first muffler had a ring and two down pipes and failed due to the vibrations from this engine. the new version is steel with a simpler mount. It also comes with an adapter that screws into the exhaust port, then the muffler threads to that.

Arruda

Bugerdup: Thank you once again.

Have you already flown this setup?

I had problems with both the RCV and OS mufflers (the RCV looses the tip and the OS looses the pressure tap).

If the Keleo muffler resists the vibration and high temperatures involved it will be a success.

bugerdup

Yes, the back of the muffler has a bracket welded to it that uses the lower mounting bolt holes on the engine so it does not move. I have run this set up with great success and It sounds awesome.

Although my engine configuration may be different then yours, (starter on the side) Let Kelvin know when you order, (stock or rotated). He made the bracket to fit my setup.

andi3142001

Hi guys,

the following story could maybe bring some light to the vibration issue. Some days ago I had a crash. "Landing" was out of sight, damage was minor, but evidence showed that the plane has hit the -soft - ground nose first. After inspection, the engine was clean, I noticed that it was much harder to turn over by hand. Made a test run - vibrations were awfull. My SP was always a smooth performer, but now it was shaking like hell and rpms were poor.
A flying buddy, who was interested to see the inside of the engine since the day he saw it first installed in my plane, disassembled the engine, and before I could do something against it he took a piece of hard wood and a hammer, placed the hardwood onto the gear of the cylinder jacket, and applied two gentle hits.
Assembled again - the engine was easy to turn by hand. Fired it up - no vibrations, performance as ever.
I have no equipment to measure the play in the gear. But obviously its fundamental to engine behaviour. I do not know wether my buddy was just lucky to get it right, however there are certanly some tolerances. According to his opinion it is important that there is no play when you turn the prop, the starter screw has to turn instantaniously.

regards
Andi

donddsms

My Feedback: (1)

Hi 120 guys,
I am happy to finally find this thread!

I bought two new RCV 120's about 8-9 years ago, for a VQ P-61 ARF. At the time I had read glowing reviews concerning scale performance and reliability, and the fact that the engines fit neatly inside a cowl. I broke them in on the bench over two hours each. After completing the model, it sat in my basement until recently. I decided to revisit this old project, and thought it would be a good idea to try one engine out on a single engine arf. It's in a Seagull Yak 54 90 size. I have a 4 bladed 15.5/12 prop, intended for the P-61.

During break-in run I lost several muffler nipples, and the mufflers reliably came unscrewed. I assumed the vibration was from the axial movement of the piston, but after reading this thread I realize there is a lot going on inside that engine.

During a ground run with the plane secured, the engine overheated. The aluminum spinner was nearly as hot as the muffler. The muffler was on the grass. Also, the tabs securing the canopy to the model both broke due to vibration. Got those tabs fiber glassed and epoxied down now.

I have four flights now on the Yak. The first flight was exciting and noisy, ended in a dead stick with the muffler nipple missing. And the pilot figure lost his head, it rattled right off his shoulders.

That evening I put 5 layers of fiberglass securing the firewall to the box, and one layer inside the box. Yesterday I removed the cowl, ran the engine and re-checked the low needle. Mine seems to run best at 2 revolutions open. The high needle is about right at one revolution. I re-tightened the muffler while it was hot, as per the manufacturers recommendations. I am using

I had to make a cowl baffle using a Quaker Oats cardboard container, and also opened up the grill vents and epoxied window screen painted yellow to camouflage the hack job.

The high speed needle needed a long extension, and it vibrates like crazy when the engine runs. I don't think this will hold up long.
Flew her again, and the muffler was once again lose but was retained by the vent hose.

I will try the Great Planes vibration isolation product you recommend, and I want to get that muffler too!
These engines were very pricey, and I have serious concerns about flying a twin powered by jackhammers. But as I am this far into it, call me stubborn. I want to make this work. Any other advice from you with experience will be appreciated.

Don

buzzard bait

For the high speed needle extension, try using something like an inner Nyrod tube. It will need something to go through at the top, but at least the vibration won't cause damage or metal fatigue in the extension.

I have a 60SP I've been sitting on. Really want to use it, but the problems worry me so no plane for it yet.

Jim