gasayers

Please bear with me. I really want this engine to work. It starts, idles, runs, lots of power etc fantastic.
I ran it for 2 hours today, (at least 1 3/4 hours actual running) and it's had at least 40 minutes prior to that.
Prior to today and mounting a flex exhaust, best I could get was 5 minutes before something fell off. Exhaust, Motor mount screws, exhaust, exhaust,
Two hours today and zero issues!
At the end of today it was certainly smoother running than yesterday. If I run it another 60minutes can I realistically expect it to vibrate even less? That’s already over 2 ½ hours running. (used about $50nz gas which I don’t mind while it’s improving the vib issue).
Cheers
Glen

ktcanuck

I am starting to get spooked. I have an unrun 120 sitting in my ready-for-paint TopFlite Bonanza. If this thing is going to vibrate like hell I am not going to be a happy camper.

Just how bad is that vibration, Glen?

gasayers

How do you quantify a vibration? I guess it's quite subjective.
When tested a week ago it was vicious. So hard you couldn’t hold the test stand. Part of the scale cockpit and the exhaust fell off after just two minutes ground run. I surmised that it would literally destroy the integrity of the plane if flown. Now the shims removed and it’s been run another 2 hours it's questionable as it is definitely smoother and some people do say they can take 3-5 hours to come right.

Very frustrating because in all other respects this motor is great!!!!

What I need to do is throw this onto an old airframe and fly it a few days. Trouble is the airframe tagged for the job was crashed by its owner a month ago. (Big old ugly stick)
Remember some people aren’t having issues and love the engine.?!?
It is amazing how little info is around regarding people actually flying RCV’s. I hear of people but don’t see them. Did see a guy running a CD the other day. Compression was near nil but it ran smooth as silk and hauled the plane around the sky easily.

Cheers

PS ktcanuck don't even consider flying without a minimum of two hours bench running as per the instruction. Thats a fact.

andi3142001

Hi Glen,

do you have an older version of the SP? On the ones sold now they changed the gear, never owned an old version but it seems to make a difference.
I run an 120SP now for 3 seasons, and would not say that there is a difference regarding vibrations compared to other fourstrokes.
They all shake
What I do believe is a difference is the doubled torque, that tries the engine to distort on the bulkhead. If the screws are not tight enough and the engine gets some play things get rough. I had to reinforce the bulkhead, it really has to be rock solid as any weakness will result in movement and loose screws.

Cheers
Andi

gasayers

Thanks Andi. I think your referring to the helical gears instead of the original straight cut gears which gave some issues. Mine has the better helical cut gears but still had the shim to adjust gear play. Not the latest twist adjustment.

Cheers

ktcanuck

I would never fly without running in on the ground. But I was planning on running in with it mounted on the aircraft. I guess I will try it. If it is too bad it gets remounted on a stand.

Keith

andi3142001

Ah ok. And yes, the engine gets more "civilized" after break in.
Which fuel do you use, how much oil and nitro?

Cheers
Andi

Arruda

Well guys, I have an RCV 90 SP and it does vibrate.
Actually it is a different vibration (a torsional one) from other 4 stroke engines.
After 2.5 gallons running on the bench I installed it on a World Models Super Chipmunk 60 and did some reinforcements in the firewall, but not different that I would do with any other ARF plane.
The firewall resisted very well. The problem I had was in the front wing junction with the fuselage. I had to sheet the wing with aluminum and some fiberglass.
I don’t know how long the plane would last because after six month I hit a dead tree and lost it (no, my name is not Charlie Brown).
I had a lot of problem with the muffler. I had two originals and then changed to an OS. The OS is lasting but the pressure nipple didn’t resist the heat and I had to drill and tap a bigger one.
I’m looking for a new plane to install it. The engine is worth it. Has a fantastic noise, is very economical and with a lot of power. And, of course, disappears completely in the cowling.

gasayers

10% synthetic, 5% castor, 10% nitro.

Regarding heat at the exhaust, I've changed to an os flex and seriously, on the test bed, I can hold the exhaust just two minutes after stopping the motor. The ribs on the flex transfer heat away from the motor and exhaust like I cannot believe. And it solves all the exhaust vibration problems. Definitely worth putting on.
I'm thinking of adding a small flywheel to the propeller to help smooth out the ignition but can't help thinking that massive gear should already be doing that.

Keith, and I'm not being even slightly negative about the motor. Don't even think about running it in on the airframe. It's not even worth trying. During run in they are unbelievable messy, do your plane a favor, take it out anyway. This has nothing to do with issues. Just running it in. Mount it on a saw horse, take it out into a field somewhere, take a flask of tea, set of earmuffs and a couple of your favorite flying magazines.

Regarding gear backlash. I can't measure it but I'd guess, on a 15" propellor, the play is close to but not 1mm.

Cheers

andi3142001

Yes, had the same trouble with the muffler. OS is better, but the pressure nippel tended to unscrew. Now its soldered.

Thanks for the input with the flex pipe, I will try that.

So the fuel should be fine.
Have you tried playing around with the low speed needle? Even if transition and idle is fine, just a small change could be an improvement vibrationwise.
I tried several props, also light wooden ones. Made no difference in vibrations, however the idle was a tad smoother. And they have to be balanced, of course.
But the best advice, I guess, is to bolt the engine as firm as possible to the firewall to lead the vibrations into the fuselage.

Cheers
Andi

ktcanuck

I will take your advice and run in off the aircraft. The engine's out right now for sanding and priming of the airframe anyway so no time like the present.

Keith

barry wetherell

Guy's interesting reading all of the above, I am/was planing to put 2 rvc's into Vance's Whirlwind, but the vibration you guy's are discussing is a bit of a worry, why do they vibrate so much?????, I would have thought the inline arrangement would have reduced that level.
I have been running OS 4 st for a number of years, and yes one has to strengthen the firewall, but the way you guy's are talking,looks like one has to mount them onto a brick..............not so sure now that the rcv's are the way to go.[sm=50_50.gif]
I am disapointed, but maybe it's not all that bad????????
A.A Barry

andi3142001

Well its hard to tell from the distance, and even harder to compare vibration levels.
Here is a pic from the installation of the 120 SP in my Chester Jeep. Its not ideal since the firewall is supported from only 3 sides due to a big hatch. Firewall is 6mm ply glassed to the fuselage. The firewall is sandwiched between motor and the alu backplate.
So that works fine, its rigid enough.

Cheers
Andi

bugerdup

I have more then 3 gallons of fuel through mine on the bench, and it has calmed right down. When I first started and ran the engine for the first time, it would vibrate my field box right off the table. but now she runs quite smooth. It seems to be a 3D vibration coming from the torsional force of the prop and the unbalanced force of the piston and crank counter weight. I did buy a Great Planes rubber fire wall mount but have not tried it yet. The rubber grommets are very stiff with large mounting hardware. I know it says not to use one of these but what other choice do we have.

here is my set up on a Top Flite Corsair.

andi3142001

I guess what could - could work is to mount the engine on the firewall, and to have the whole firewall vulkanised into the fuselage.
So there would be only little way for movement, but the rubber could take some energy.
Do you start your engine with the adapter, from the side?

Cheers
Andi

bugerdup

yeah, I rotated the lower half so the socket is on the side, just for my preference. I really love this engine and plan to buy another for my P 47. Once it's broken in and tuned it's one bad mother, swinging an APC 15.5x12 4 blade prop at 5800rpm.

andi3142001

Yep those engines are ingenious. [8D] Beside some small electrics I own I will buy only RCVs in the future.
Concerning vibrations, have a look at the gassers. There are some models in my Club with gas engines - the whole tail gets blurred when they start hammering.

For my next project I consider to rotate the engine by 45 or 90°, as you did, and to make a hatch as access for the adapter. So its good to know it works without slipping off with the starter.

Cheers
Andi

ktcanuck

Bugerdup, that's a neat install. What glow plug connection is that you are using?

Keith

bugerdup

Good eye, believe it or not it is a wheel collar with a wire soldered onto it. I used a small fiber washer to space the collar off the plug and use the set screw to hold it in place. so far I have had no problems. I kept reading stories about regular plug caps falling off, and this was one of the cures mentioned. simple, give it a try.

barry wetherell

Bugerdup, that is ideal, good thinkin'
A.A. Barry

gasayers

When you turn your motor over by the prop slowly, can you feel the gears cogging. Half my rotation is dead smooth and half cogs.

bugerdup

When I first ran the new engine I did notice this and found that metal filings were jammed in the gear teeth causing hard to rotate. It might need cleaning by spliting the case and cleaning the filings from the gear teeth. I have not had a problem since.

barry wetherell

Gasayers, that dosn't sound good, I would hate that to be the case with the new one that I have just bought, making 2, B.Up has the solution but the manufactures should be notified, for their future reference, I would think
A.A. Barry

gasayers

Thanks Barry.
I have a couple of problems. One being NZ is a long way away and the local dealer I got the motor through is gone.
Secondly, like a few people, I bought all the gear about 4-5 years ago but have only just got around to fitting it. So it's way out of warranty.
To be quite honest I'm putting 2x 5cell 3300mah Hyperion batteries in with a Z5025/22 215kv out runner. (1500-1800W 2500peak) 85 amp opto controller (this is all gear I have at hand for various reasons) This'll give me twice the hp for just 200grams more, no vibration and no hassles. Disappointing but I feel like I'm beating my head against a brick wall.[] No other motor I’ve played with has taken this much work,
$800NZ for the motor and another $120nz for fuel running it in, $60 worth of props and $100 for the exhaust system. (yes you did read that right.) Just to ditch it for another set up kind of hurts. Runs like a dream but just vibrates too much.
Maybe I'll get back to the RCV later.

I'd have to say my other dissapointment is there's no "RCV Technical Support" active on this forum. In the OS forum your not even allowed to discuss. It's only technical support.

andi3142001

Hi gasayers,


what I guess could be worth trying is to get rid of the castor. According to my opinion it does no good to the SPs.
On my SP120 there is also a different feel in the gear when turning the prop. I do not know the reason, maybe its the different wear since its its always the same teeth that take the power from the piston.
But it runs smooth and powerful.

Cheers
Andi