R50 Juddering.

[jimbob]

Got a problem.

Rebuilt the R50 following a large pile-up last sunday and just tested the hover.

At higher headspeeds I get a intermittent but marked judder, more often with -ve pitch applied than +ve.

All the head shafts are new, and the head tracks with no wobble. New blades/boom etc.

I am looking at the one-way bearing, and it appears that one of the bushes may have been pressed in a little.

How do I check the bearing, should this bush be inset, and could it cause the problem?

Heeeeeeeeeeeeeeeeelp Meeeeeeeeeeeeeeeeeee

[mackem54]

hi there, last week i had a similar problem,when i increased throttle and then lowered the throttle i got an intermittent judder when she was descending, altered my throttle curve and i have never had it since,
hope this helps

[Ade_Law]

how tight is the tail belt? It should be tight without being under tension.

check the bearings on the mainshaft, blade grips first. if the machine has had a lot of use also check start shaft and pinion bearings.

the way i check bearings is to take the bearing out, put it on a shaft then twist the bearing slightly (loading it) and rotate it. if you feel any roughness its a dud.

Ade

[jimbob]

I like the 'tight but not under tension' part

The head is almost new, although was in the crash - its possible that one of the bearings has failed...

I go by the TT description of no more than 5mm of movement, altough frankly, thats a bit arbitary isnt it.

I guess I need to check all the bearing again.

I have a head that wasnt in the crash, so might try that tomorrow (rain permitting).

Thanks for the help so far

[jimbob]

Something else.... which way round should the thrust races go? The manual says the smaller diameter goes towards the blade but doesnt say about the races.
Also, should it be lubed?

[Steve]

Check the alignment of your paddles. They should be exactly level with the flybar carrier, or pointing slightly down, but definately not up.

[Ade_Law]

it doesnt matter which way round the balls/cage go in the races. Paddels should be perfectly aligned with each other, any incedence will give issues with trimming the model.

Ade

[Janek]

The thrust races must be well greased, and so should the damper rubbers

[jimbob]

Well I think I figured it out.

I dried out the auto gear some - it was pretty greasy and could have been slipping.
I reduced the belt tension slightly.
I leaned the engine a little bit.

I dont know which it was, but its all ok now.

Oh, one last thing, I sprayed my canopy purple - I think that may have been the clincher in the end...

If I could work out how to, I'd post a piccy.
(update - made a gallery so you can see the purpaliser)

Thanks for all the help.