martyg

My Feedback: (42)

Is engine soft mounting feasible on a profile plane?

Here's the deal.
The Saito 72 on my SuDoKhoi vibrates -- A lot.
Foams the fuel something fierce. Engine is sucking in a ton of air.
I'm settting it plenty rich on the ground - Comes back super hot.

Engine is on good and solid. Tank is side mounted over foam.
Experimented with types of foam and rubber band tension.
Moved it around further away from the engine too.
Have swapped out tanks and lines. Pressure tested them too.
No dice.

Props are carefully balanced on a High Point.
Engine has 4 gallons though it. OS type F plug. Valves at .005".
Low end is good - Idles beautifully - Great throttle response.
Tried a bunch of fuels - I'm now on Powermaster 20/20.

Now I'm foolin' around with bladder tanks.
This seems to help, but is a total pain. I just want to fly this thing.
There's got to be a better way. Any ideas?

ChuckAuger

My Feedback: (12)

Your engine isn't out towards the front of the mounting beams, is it??

It's not an ARF is it??

I got slam hammering YS 63's on 2 (soon to be three) profiles and the only profile I've seen a foaming problem on was a Goldberg 330 ARF.

Wish I had more to go by....if it's shaking that bad then something isn't stout enough.

beenie

My Feedback: (9)

I had a similar problem with my Lazy Bee and a Magnum .30 4-stroke. It didn't vibrate all that much and was soft mounted. I wrapped the fuel clunk with felt and used .020 stainless wire to secure it. The felt creates an "bubble filter" and the engine should only suck fuel. Sounds a little crazy , but it worked for me.

martyg

My Feedback: (42)

beenie,

I think most of my foaming is coming from the clunk slamming the sides of the tank. Tried two 6oz tanks with different wall hardnesses - A Hayes (hard) and a Great Planes (soft).

Wrapping the clunk to reduce impact shock is an intresting idea.
If the material removes bubbles, that's great too!

I'll see if it runs good today on bladder tanks.
Once I have a solid baseline, I'll try your suggestion. Thanks.

ChuckAuger,

This is a buit-up kit - Front end seems really solid.
Engine is mounted as far back as it can go.

mc71

YS sell a commercial bubble filterfor a rediculous price, I tried stopping the foaming on my profile but to no avail. What I did was cut a chunk of foam, then cut a hole in it for the clunk to go in, wrap a piece of plastic around it and pop a few holes in the plastic, same effect as the felt idea, works great and sucks every last drop out of the fuel tank.

Matt

Gordo-ProBro

There is a filtering clunk (dubro?) that is very cheap and solved this in a super light racer I had years ago.

I went to Tower and here is a link to it:
http://www2.towerhobbies.com/cgi-bin...?&I=LXD741&P=0

Worked for me, $2.00 worth a try!

Gordo

tetherite

Try mounting the prop at 90 degrees to when the piston is at top dead center. This may help a little with the vibration. And check the prop balance!
My $0.02 worth.

nocg

My Feedback: (1)

I always run a filter in the line. I think the fine mesh helps break up some of the bubbles.