Jake Ruddy

My Feedback: (40)

haha! I only had one of those

juanes1969

you`re right sinergy, the engine vibrates in a normal way for a single. I think I`m going to take your advice and just run the engine a little more until it gets broken in. The needles seem to be fine where I left them, good transition, holds idle and good power at full throttle.
Someone recomended that I try to install the prop in a more vertical manner, I don`t know if that would help any, but that position makes it really dangerous to start by hand. When you finish going thru the first flip, the other prop blade is very close to your hand... or your face if you have to bend over the plane too much. so I will just keep running it and wait to see what happens after a few more gallons.

John

bajaloya

I ran my engine first time today. It is the 3W85CS. The CS is supossed to be harder to break it in, but as a matter of fact, vibration was not so bad?. Some of my 50cc single engines shakes a little more for its size.
I have opened the (L) to less than 1 ( to about 3/4..) from fully closed and the (H) to about 1 turn. I ran the engine on the plane with the wings off. I guess after a gallon it will perform much better. The tillotson carburartor make a real difference. Transition is great. The vibration was as expected for a big single and I am sure it will become softer after some gallons.

yakman

When I was young I raced 500 & 600cc motorcycles. These had a single cylinder and were called thumpers. Can you guess why?

ram3500-RCU

My Feedback: (221)

I have never had a Mejzlik prop that didn't need balancing. And if the tips were on (most are not) the hub was out. I would do a very careful balance job and see if it doesn't help.

arobatx

You are exposing your fuse to unnecessary vibration by running the engine with the wings off.

bajaloya

I know. ...that was part of my test: Wings off.
With the wings on and a few gallons, it will be much better.

DALE PABAJO

yea dude I did the same thing with my engine giveing it an initial brekin with wings off and the vibration shook everything off. even strip one of my servos but I didnt hve the battry connected.

juanes1969

Guys, just an update.
A cousin of mine called Aircraft international (talked to Gerhard?)with regards to the vibration problems I was having. The vibration was so bad that the muffler came loose and lost three screws. The ignition hold downs (legs?) broke off and the pilot ripped off the base inside the cowl. thank God the plane was a little nose heavy, because the pilot went to the back of the fuse (all 6 ounces of it!) and was able to land safely.
The advice I received from that call my cousin made was " Is the engine box well reinforced?"
As you can see from the pictures on post #20, I took off some of the material on the top hatch of the engine box in order to have axcess to the carb.... BIG MISTAKE!
The engine box was solid if you pulled hard up and down, but it did have a little movement to the sides. It was difficult to notice just pushing and pulling to the sides by hand, but I guess the frequency in which the engine fires and the force of the combustion does twist the engine box causing the whole plane to vibrate like crazy.

I made some new hatches for the engine box (on top and on the bottom) that were a little bigger than the engine box itself, somewhat triangular at the base where it touched the round cowling former.
After I reinforced it that way I installed the cowl again and assembled the plane. Started the engine and guess what.... No weird vibration!!!
Now the engine vibrates like a DA50, 3w80 or the ZDZ80rv.

So, if anybody has this problem with a big single cilinder engine like the 3w85, don´t rely only on the stock engine box, take your time and reinforce it. It only adds some 2.5 ounces to the front, but with a big single like this one it is worth it.

Thanks to AI for the good advice!

Just wanted to let everyone know how my problem was solved, I hope it helps.

<John

bajaloya

I have a very hard engine box. (If the plane crashes, the engine box will remain the same). The engine is getting softer after adjusting and burning some tanks. It is a bit of a shaker, but I think it is normal. Great that you have fixed your problem.

AFSalmon

My Feedback: (3)

Just got one of the new 3W 85s and plan to mount it on a big yak. Problem is I need about 3/4" worth of standoffs. The 3W manaul says to mount directly onto a firewall or risk distorting and damaging the crankcase. I guess I could cut 3 pieces of 1/4" a/c ply and build up the firewall and engine box but this seems like a rediculous approach. Is using good machined aluminum standoffs a problem? Need ideas please.

arobatx

Did you buy the aluminum engine mounting plate for the 3W? If so, you can trace it on layered ply, and cut out a very nice and light spacer to use.

AFSalmon

My Feedback: (3)

Nope, did not know about that.

arobatx

Here's a picture of one.... get one from www.cactusaviation.com or www.aircraftinternational.com

Patto

I just bought a 3W85xi a couple weeks ago and put it on a 33% Yak 54, (upgraded from a 3W70). I didn't need standoffs, but my understanding is that 3W recommends you don't use standoffs directly mounted to the engine. If you use the $30 mounting plate, you could probably use standoffs without any problems. Just mount the engine to the plate, plate to standoffs, standoffs to firewall.

For what it's worth, I reinforced the heck out of the engine box and made a new firewall for the Yak since the old one was getting a little worn. I thought it ran really smooth at all RPM's and was really impressed by how little vibration it had. I think the advice about the box being a likely culprit is really good advice.

The 85 has a lot more power than my strong 70 had, even though it's only had two tanks of fuel through it. I look forward to continuing the break-in process next week. I don't think I'll ever be able to buy another brand of engine after this. Between the 3W70 and now the 85, I just can't imagine being happier with an airplane engine. I haven't even touched the needles on the 85 yet. They were perfect straight from the factory.

-Pat

juanes1969

P-Diddy, you will have a lot of fun with your set up, this Yak is incredible with the 3W85.
For everyone else that has the vibration problem, if you reinforce the engine box especially on the sides, you will experience a lot less vibration. This engine does not shake more than any other engine.
You can use standoffs with the mounting plate, juts make sure that when you tighten the bolts to the firewall, that the standoffs don`t try to go into the wood on the firewall since this will make for an uneven fit and could always distort the crank even with the alu plate.

John