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01-18-2009 08:48 PM  9 years agoPost 1
pgkevet

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Wales

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I flew Preddie about a week ago (he takes turns with weather and Spectra's go). He flew really well for the first 2 flights despite my recent confidence pussy-flying issues...just circuits and loops and rolls. On the third flight there was a sudden change in engine tone..a pitch increase in note and I landed quickly thinking the the muffler had loosened..but it didn't have that tinny lean sound.

..checked everything over and it looked OK so fired up again ..but not getting headspeed for expected engine sounds and called it a day wondering if the fan might have loosened on the taper.

I finally got to pulling the engine out and all 4 clutch bolts are missing.. and yes they were locktighted in!

Ho-hum.. I get to dial it all in again...

As for Spectra..well it was pretty gusty today but I needed some flying..so fuleled him up and fired up.. He got to midstick without any clutch engagement, the engine sounding slow and rich. I eased up to a takeoff at 3/4 stick but the headspeed was still low and I promptly landed and gave up. There have been no changes to linkages or settings.

When I've finished fixing Preddie then I'm going to have to rework the linkages here and perhaps pull the engine and look at the clutch. I did have a hot start once with Spectra and it's been nagging at me..

pgk

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01-19-2009 12:19 AM  9 years agoPost 2
Fixit

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UK

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Hi PKG

What air filter are you using on the Spectra? I had a similar problem and it turned out the choke had closed slightly.

The trouble with the Predator clutch bolts is now you’re going to blather them with locktight and swing on the allan key then the buggers won’t come out when you want them too

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01-19-2009 02:55 AM  9 years agoPost 3
pgkevet

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What air filter are you using on the Spectra? I had a similar problem and it turned out the choke had closed slightly.
Stock..but no sign of it having moved..unless the filter itself is clogged (haven't taken it apart yet)
The trouble with the Predator clutch bolts is now you’re going to blather them with locktight and swing on the allan key then the buggers won’t come out when you want them too
I swung on it last time!..

pgk

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01-19-2009 11:34 AM  9 years agoPost 4
Fixit

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I doubt it will be the foam filter but the mesh filter in the carb may be clogged, when using the felt clunk you can get fluff on the filter now and again.

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01-19-2009 12:52 PM  9 years agoPost 5
pgkevet

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..i'll finish preddie first then have a look.. but it was rich at low revs with smoke and not picking up fast enough. We'll see what it looks like inside in due course..

pgk

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01-19-2009 02:38 PM  9 years agoPost 6
pgkevet

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Preddie clutch

Now I've had a chance to look at it closely.. two of the M4 bolts have sheared in the clutch holes and plugged them with nothing to get a purchase on. There's not enough metal to drill and retap if I sourced the taps. I can't say I'm keen on redrilling and tapping the older M3 holes for the sake of it (for those than don't know the HD clutch has a set of each.. sorta looks like old stock stuff redreilled as an upgrade).

Unless anyone has a better idea I'll have to try going with M3 bolts wrapped with aluminium foil as they go through the fan to sleeve out the gap.. or hunt up some 4mm tube with a 3mm ID - but that might be harder to find.

But if M4's sheared then what chance to M3's have? Or chance that it just happened because two bolts worked loose? One of the issues is that the clutch was never a tight fit into the fan anyway so a potential for movement but not a big enough gap to sleeve there and wrapping that with foil and piercing holes is going to be nigh impossible...perhaps some thick CA painted into the hub?

I suppose if it all goes ****-up then it's an excuse for a super fan...

pgk

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01-19-2009 04:05 PM  9 years agoPost 7
pgkevet

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....looks like than won't work

The fan dials within 2 thou on the fan outer rim and marginally better than that on the top outer flange edge of the hub but way, way out on the inner hub. It doesn't look chewed in there but I assume the sheared bolts have lapped it irregularly.

There's way too much slop on the clutch shoe itself when trying to bolt it in with M3's and however I try it in the 4 options it's a long long way out..

..gonna have to think about this...

pgk

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01-19-2009 08:43 PM  9 years agoPost 8
pgkevet

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..gonna have to think about this...

I'm going to try with heat and screw extractors (ordered.. be a couple of days) to see if i can get the scraps of M4 out of the clutch.

I've been playing with tape and tissue paper wrapped around the clutch to take up the slop and it does appear to seat better. I turn of insulation tape is marginally fat. My 'game plan' will be to go with PTFE tape (when bought) since any shards getting into the threads can only be beneficial and it's thin enough to be a couple of turns. Then it's a question of whether i can get an acceptable run-out.. otherwise it's a new fan hub <sigh>

pgk

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01-20-2009 01:36 AM  9 years agoPost 9
jschenck

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La Vista, NE.

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Were the clutch bolts long enough?

http://runryder.com/t409721p1/

My Pred. is almost done but since Nebraska is frozen solid I haven't found the motivation to finish it up. Almost there though.

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01-20-2009 06:22 AM  9 years agoPost 10
pgkevet

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Wales

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Were the clutch bolts long enough?
The frst clutch I had I couldn't find the bolts in the kit and used some flat pan-head zinc plated bolts from the local hardware shop that I cut down. The heads never sat as nicely as I'd like but it worked. After my first attempt at reversing the torrington when I bent cne of the clutch shoes and straightened it I decided to buy a new clutch.. even though the first one worked fine.

Second clutch came with a bolt set which I used. The length is such that where they have sheared then they are flush to the inside face of the clutch but sheared about 1mm from the outer side.

If they had been longer then I might have been able to pull them through.. but they are the right length.
My Pred. is almost done but since Nebraska is frozen solid I haven't found the motivation to finish it up. Almost there though.
My enthusiasm for flying in winds greater than 25mph pretty low too.

pgk

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01-22-2009 07:47 PM  9 years agoPost 11
pgkevet

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..getting the sheared bolts out was a non-event.. my extractors arrived but the bolts spun through while drilling the pilot holes.

..now to re-dial and try the ptfe idea..

pgk

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01-22-2009 08:11 PM  9 years agoPost 12
j.8

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Denmark

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Hi

"..getting the sheared bolts out was a non-event.. my extractors arrived but the bolts spun through while drilling the pilot holes."

That`s good news pgk

Regards Bo

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01-23-2009 08:05 PM  9 years agoPost 13
pgkevet

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4 hours of dialling!

Well to qualify ..I decided to check the fan as is on multiple facets.. the top face of the upper fan ring was around 2 thou. The side of that ring was about 3.5thou.. the lower ring outer edge was 1.5 thou and the top of the centre hub around the inner flange was also about 1.5 thou. There was no pijt trying to dial around the inner edge since it's marginally chewed.

the clutch itself was a pig. I wrapped 2 layers of PTFE tape around it and that sat it in firmly..but how to dial it? It finally ended up being a long slog combination of dialling the top face to consistency and then the sides across the solid dimeter of the hub BUT trying all the 4 hole combinations for best fit was very frustrating .. there is enough rocking movement on the fit that it fnally ended up as a combination of working out the average dial indication and manually holding to that figure as each bolt was tightened a bit going around...on about 5 hole attempts (yes the first one was the best:mad... but getting that top face within 1.5 though wasn't the end.. get it right and cross-reference with the sides.. and start all over again until that best fit was achieved.

And of course I hadn't applied the locktight and had to go around again when the best fit was determined with a combiation of dogging it down then loosening and retightening in turn until the best fit was achieved. It's within a thou on the top surface outer edge and within 2 thou across the solid part diameter. Well actually it isn't because that figure varies depending on whether it's top, middle or bottom from the side. but that's the worst case.

Anyway.. I'm happy despite the slog... so long as these bolts don't shear..galvanised steel from the diy shop

pgk

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01-23-2009 08:26 PM  9 years agoPost 14
jschenck

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La Vista, NE.

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I never check the top face of the clutch, perhaps I should but I figure if I get the side of the clutch as close as possible and the fan hub is on straight the rest will work out. Now I don't KNOW if that's true. My last build had a pretty smooth running clutch though (I think anyway) of course I don't have too much to compare to.

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01-23-2009 09:00 PM  9 years agoPost 15
pgkevet

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.trouble with clutch side is that there's only one measurable diameter. It's all I've done before since the shoes will open up anyway - but with the slop of clutch hub to fan hub here I needed an extra reference

pgk

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01-26-2009 03:41 PM  9 years agoPost 16
pgkevet

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Wales

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Predator - Sigh! Pre-flight. range test, Test fire.. engine OK, clutch:bell fine.. gentle throttle..no probs.. Short hover then gentle circuits then a bit more circuit and a loop.. all working fine. Next flight ..still pussy-flying but higher and further and suddenly it's banking left side down and slowly turning left.. full right aileron and it's still at 45 degrees left list... moving away from me towards the woodland...

A better pilot might have known what to do but frankly I sighed and dumped it away from people...

Worse is that the cyclic servos seem to be working and the links to the swash are OK ... others suffered in the crash along with the usual attrition... So I can't be sure why I lost aileron. Will have to load test servos when rebuilt I suppose? Jammed swash that freed itself on impact? Canopy shifted and jammed the cyclic? I don't know. What I do know is that it's £250 and 20 hrs work :cry:

Easy after the event.. throttle hold, spin it round and glide,auto back towards myself or fly the wide circle until it's better postioned and auto... but by the time I'd faught aileron and given up on it it was a good 100yds out...

Just call me lucky! I had the throttle servo short internally on my 600N last week and failsafe cut the engine... that auto was good - just broke the skid bows on a slightly hard touchdown in the rough

pgk

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01-26-2009 05:39 PM  9 years agoPost 17
Fixit

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Dam that’s bad news, you don’t seem to have much luck with your Predator I have to say.

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01-26-2009 05:58 PM  9 years agoPost 18
pgkevet

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Wales

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Dam that’s bad news, you don’t seem to have much luck with your Predator I have to say.
..Lots of luck... just mostly bad...

...shows me up for considering my good fortune at spotting the clutch failure in flight and landing last week..

pgk

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01-26-2009 11:43 PM  9 years agoPost 19
Rainmaster

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England

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dont forget to check reciever crystal My Spectra did the same thing last week but hit throttle hold and it worked found a failed reciever crystal "VIBRATION"

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01-26-2009 11:55 PM  9 years agoPost 20
pgkevet

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Wales

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dont forget to check reciever crystal
Futaba 2.4...

But interesting that a glitch would affect just one channel?

pgk

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