MOTOR VIBRATION ?? killing my planes...???

[GremlinX]

Man, I first off, want to say how incredible these motors are! I love me some DA now... However, I have 2 50cc ARF's and both have had a motor box come apart. They are both very name brand and very quality kits. I pinned the firewall, and it will eventually break itself somewhere back upstream from the mount plate. I rechecked the prop and it is dead on, including the hub. I am running the stock standoff's which I think cause a lot of the problem. BUt the planes were built around this length . So, everything is balanced, the motors are tuned very well and run strong. I know it is a single and will vibrate no mater what.... but this is literally destructing my 2 planes. Is this normal to be repairing the mount boxes after only 2-3 gallons? The glue joints and all are not coming apart..... both planes(made by 2 completely different people) are just cracking the sides of the mount box. Last night the whole both sides broke and the motor had 20 degrees of down.... It harriered well though.... What am I doing wrong???

[TheTank]

Theres definetly something goin on there. If you pinned the firewall, you should be all set. Are you sure your not running a little rich on the low end, causing it to vibrate a little more than usual? Also, I would hardwood square stock, put it in the corners where the firewall meets the cheek plates, and then pin/bolt through that from the front and the sides. I had about 15 gallons through my 50cc Yak with no problems, 10 or so gallons through my ultimate, and 15+ gallons through my WH Extra, all with no problems.

[Supermod56]

Not saying you don't have a motor issue, but what I do is laminate the whole engine box with carbon cloth, and use sheet metal screws instead of pinning the firewall. The button head Du-Bro screws work great

Tom

[Cracky]

not to be silly, but are all of the standoff's the same exact length? When I got mine they were slightly different lengths...not by much, just noticeable when put on a surface plate. You could be twisting the firewall if they are too much....

[matus777]

Also so if your firwewall holes do not have a tiny bit of play with with the standoffs mounted & partially secured you could be putting stress on the case, resulting in vibration. Engine & standoffs should have very slight play before cranking down the bolts for final mount (SLIGHT).

[TazmanianDevil]

Hey bro use a fiberglass cloth around the engine box this will give it much more flexebility and strength or CARBON if you got some
I do it to all my birds
If you need to join the box again use GURILLA GLUE the best in the west for these kind of things

[3daviator]

I would say not normal. Did you buy the mtr new? No prop strikes? Did you indicate the prop shaft for runout?

Keep us posted. I'm putting together my first gas plane with the same mtr so I'd be interested to see what you find out.

Good luck

[btomlinson]

	Quote: Originally Posted by dgfick
	not to be silly, but are all of the standoff's the same exact length? When I got mine they were slightly different lengths...not by much, just noticeable when put on a surface plate. You could be twisting the firewall if they are too much....

How much of a difference ? Are we talking a few thousands or was it over .010 ? IMHO they shouldnt vary over .0015 max.. This could also be a engine balance issue


Brian

[Cracky]

	Quote: Originally Posted by btomlinson
	How much of a difference ? Are we talking a few thousands or was it over .010 ? IMHO they shouldnt vary over .0015 max.. This could also be a engine balance issue Brian

I don't remember how much off...it was 3 years ago and I didn't have them measured before they were ground to the same....

[GremlinX]

Ok, back home... from work...uggg.
Standoffs the same, no prop strikes, and am lean on bottom now that I have 5 gallons or so now. This is 2 planes,2 motors,2 sets of motor mounts.. the works. I mean honestly guys, a 2" standoff is very cantilevered out there with poor geometry to begin with. You have to agree a 1/2" stand off would be stronger than a 2". Anyway, The mount box is not breaking! Go back behind the F1 and where the fuse "side" is(eventually becomes the box sides as you near front). Its just cracking the side of the motor box, but back inside the fuse. The latest one is a very light weight laser built ARF... so... I am skeptical that the light fuse is taking its toll. Both planes were bought used, so I cant say how many hours. One has never had a crash and one has a slight crash damaging only the wings, again, before me... The more time this latest motor gets, the smoother it seems to run. Yes, both bought new, both over 5 gallons.

[fly boy 01]

I had my DA 50 rip out of my AM yak 54, which had a pinned firewall. I used gorrila glue on it, and it was perfect up untill it rippied out (obviously hehe). It is very frustrating to have issues like this, which has kept me off planes for a while.

[GremlinX]

Yes, I see... This is NOT motor box related.... its behind that, where the box sides become the fuse sides...