RunRyder RC Helicopter Topic - Maybe have got to the Bottom Of My JETCAT SPH5 Turbine problem -

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Got Jet Fuel? Turbine Helicopters > Maybe have got to the Bottom Of My JETCAT SPH5 Turbine problem -

MattJen
Elite Veteran
Location: UK

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i had an interesting email from JETCAT

it looks as if there is a fault on the HOBBYPARTS CONVERSION,
as it doesnt come with this bearing,
For those that don't know i have had an ongoing problem with the SPH5 see thread "Problem with SPH5 Really Annoying"

Hello Mr.Jenner,
my collegue Roman just tested your SPH5 and was astonished to see, that your Belt-pinion doesn't seem to be with an upper bearing! As you can see on the 16.000RPM drive-shaft of the SPH5 we have a diameter for a small bearing to take the radial Forces of the Belt-tension.
In the constructions/mechanics we are using, there is a bearing to take these Forces.
Hope you understand what we mean.

Mit freundlichen Grüßen
Best regards
Max Reinhardt
Produktionsleiter Turbinen

that is how these machines come from Hobbyparts AFIK, the fact both have gone the same way leads me to think an upgrade is needed from Hobbyparts to prevent this from happening,

Maybe PeterRob could shed some light on this?????As i bought both machines from you and there are a lot of other Hobbyparts conversions out there, this could have implications on all SPH5 conversions out there.

Matt

12-06-2007 06:45 PM

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chopper jockey
Senior Heliman
Location: uk

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Matt,
it should be obvious if you over tension the belt it could strain the output bearing. Only tighten the belt enough to avoid the teeth from jumping. Your problem was on the input side of the gearbox seizing up, not the output..

12-06-2007 07:14 PM

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Dave Hollins
Senior Heliman
Location: UK

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For potential SPH5 / Vario users.... The Vario mechanics that are designed for this turbine have this bearing fitted as standard, it supports the 'free' side of the output shaft.

http://gallery.vario-helicopter.org/gallery/Dave_Hollins

12-06-2007 09:01 PM

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MattJen
Elite Veteran
Location: UK

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ChopperJockey

thanks for post, but my belt was so loose i could take it off with my hand and for this to happen on two machines and also one other XLV with the same conversion has had the same problem, a bearing fialing prematurely.

my question is why is the shaft not supported in a bearing ? as this would cause it to flex which is something that Peter Aluded to sometime ago, if it is indeed flexing then this bearing would prevent that and stop the internals from coming out of align due to flexing - which is what has happened to mine and thus caused the spider castings to catch the internal casing thus locking up the head.

The fact that vario and jetcat see the need to have this output shaft supported in a bearing seems to say to me it will flex and cause problems internal if it doesnt.

it seems an easy upgrade to make, maybe when i come down next week me and Peter will knock up something that we could slot a bearing in to suport it.

THIS IS NOT KNOCK ON THE HOBBYPARTS CONVERSION my turbine flew lovely and was looped and rolled and held inverted with no problem at all.

Dave
Thanks for the post, on the zelous i also notice it is supported as well.
Matt

12-06-2007 09:47 PM

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chopper jockey
Senior Heliman
Location: uk

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Matt,
If your belt was so loose you could take it off "easily"with your hand, then it would not likely be stressing the output bearing. We fully tested this configuration for over a year with no problems found. I might add that even if you did stress the output shaft to such an extent that the bearing became worn, this in itself should not cause a problem on the input shaft due to plenty of "backlash". You had a seized input shaft, and the output shaft was still free to rotate with no bearing slop. Did Jetcat explain why this happened? And did Jetcat have to replace the output bearing?

Or as I suspect they were just commenting on why the output shaft was not supported the way they do.

12-06-2007 10:30 PM

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MattJen
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Location: UK

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that is good to know

But what is coincidental is that both of my turbines within an hour of each other and set up exactly the same except the acrobatic is forward facing and XLV is rear facing, both within a 30 hr period of have gone, also i know of one other XLV with low hours also where the bearing was doing the same thing catching...

From your expert opinion what would you say it was ?

I Know Peter has managed to flex the base plate on the aluminum plate, obviously on my Acrobatic which is carbon it is not gonna flex much, but would this cause a problem with the turbine where it is situated on the front of the base plate ?
if half was being unduly stressed due to a flexing plate?

MAYBE PETER WHO FLEW JETCAT SETUP FROM PROTO TYPE COULD ANSWER ?

PETER DID YOU EXPERIENCE ANY FLEXING THAT COULD CAUSE THIS TO HAPPEN?

i am very keen to get to the bottom of this, and as JETCAT support the shaft with a bearing whihc they obviously see a need to,

out of interest the Wren conversion how is that different to the JETCAT setup ?

This is not a put down of the conversion, i am just keen to eliminate any possible cause mechanically that would cause my bearing 20hrs to go until a service, to fail prematurely..

Also in regards to your comments you tested them for a year, remeber i have the 2 original machines that you and peter used, so could it take longer than a year ( 30 hrs in this case) for the fault to present itself if indeed their is a fault with the unsupported output shaft..?

12-06-2007 11:20 PM

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Coolrunnin
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Location: Manchester U.K.

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Thanks for posting that information Matt (and Chopper Jockey), it's all very interesting.

From looking at my own XLV, it doesn't look like it would take a great deal of extra work to add a support for the free end of the gearbox output shaft as JetCat seem to prefer. There are plenty of pre-drilled holes in the baseplate after all to take additional support mounts.

Oh, and it would mean changing the tank mounting system to allow the belt to be moved upward a bit to expose the end of the shaft...

12-06-2007 11:33 PM

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MattJen
Elite Veteran
Location: UK

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[quote] I might add that even if you did stress the output shaft to such an extent that the bearing became worn, this in itself should not cause a problem on the input shaft due to plenty of "backlash".

i am not quite sure what you mean, cos the way i noticed the bearing had failed was by trying to turn the head backwards, it was then that it jammed, turning the head ( in this case LHR) in forward motion it moved fine, it was when i tried to turn the head backwards it jammed up and i could hear a scratching, chinking sound - as seen on my video in the prev thread... so your comments above i dont understand.. cos if there was plenty of backlash as you say there should be then it would not jam up.. when if you watch my video you can clearly see the output shaft jamming..

I am not trying to argue or stir up anything, i am trying to get to the bottom of my problem... as to have it happen on 2 machines within hours of each other is just too coincidental for my liking.

Matt

12-06-2007 11:34 PM

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Peter Wales
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Location: Orlando Fl

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It doesn't matter how loose the belt is when the engine isn't running. When its got lots of pitch on it, one side of the belt has the full load on it and if it doesn't have a support bearing somethings gonna give.

Peter Wales
http://scalehelicopters.org

12-06-2007 11:49 PM

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chopper jockey
Senior Heliman
Location: uk

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Matt,
If you recall, I was with you when your acrobat showed this problem. The second stage was seized, the turbine wheel had jammed solid in the spider housing, presumably due to the input bearing failing. This usually occurs due to either overheating or lack of lube in the tunnel. But the output shaft was free to rotate a tiny bit in the backlash, and there was no lateral slop in the bearing or shaft.

As it happens, the Wren version has a specially designed transmission with a much shorter shaft protrusion and is therefore less likely to suffer from this situation.

12-06-2007 11:51 PM

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MattJen
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Location: UK

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Thanks Again PHil

So what in your expert opinion is the way round this ?

Matt

12-07-2007 07:32 AM

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chopper jockey
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Location: uk

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Matt,

In my opinion, your problem was likely to be the fuel pump not delivering lube to the tunnel. Let me explain...

I believe you were experimenting with the fuel pump start voltage settings, (either because you were trying another type of fuel pump, or you had a sticking pump,I don't remember which) now if you have a fuel pump not working properly, this is what can happen...

You ask the ECU for a start, the propane lights off and the exhaust temp climbs to about 250 + deg C and waits for the kero to be introduced. If the fuel pump is incorrectly set (or not working properly), this kero may not be forthcoming ( or even too much fuel for that matter) and so the start, after a period of time will be aborted. However, during this hot phase of the start, there is no lube to the bearings, anywhere.

This should not normally be a problem on it's own, however if you have a succession of aborted starts, ( because the pump is still not adjusted properly yet) the dry bearings in the tunnel can not cope with the constant heat stresses and will pack up.

I think this was the exact problem that you had. If you want to avoid this happening in the future, I suggest if you have a failed start then don't try to keep re starting until you either test the pump or find the fault. Or better still, upgrade to kero start.

With regards to an extra support for the output shaft on the Jetcat, I will look at it again, however I do not think this is a problem.

12-07-2007 09:25 AM

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MattJen
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Location: UK

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Phil

thanks for your post,

But i reliterate the explanation you have given may answer the problem for the Acrobatic, yes we were trying to get KERO start to work, but int he end i went back to gas..

i sent all my settings to JETCAT, and they came back with the answer we need to see the turbine, they did not see any problem with the pump voltage fluctuating, i even sent the info the SARA at wren, and according to their technical dept everything seemed normal and nothing out of the ordinary, surely if the pump was the problem then i would see the pumnp voltage going up and down like a whores draws,
something that JECAT wold easily pick up, as they have done before on the HOTCAT when PEter sent the stats over to them cos it flamed out

But in my case this is not happening as is shown by the stats i downloaded and put in the other thread, so i don't think it is the problem...
also your post
does NOT explainhow or why i have the same problem on the XLV SPH5 which we were not messing around with!

Your thoughts ?

12-07-2007 12:07 PM

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chopper jockey
Senior Heliman
Location: uk

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Matt,
I can't remember now, but did you change the pump from one machine to the other to help diagnose the problem??? Or was it the ecu ?

I really can not see how a stressed output shaft with plenty of gear backlash can cause the input shaft bearing to seize up.

12-07-2007 12:50 PM

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dazzaster
Key Veteran
Location: right next door to hell

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this may be a shot in the dark as i dont know what mix your useing,
but as phil sudjested it could be a lube problem so if its not the pump then perhaps your not mixing enough oil with fuel or theres a problem with the type of oil your useing?.
Darren

A.K.A 509

12-07-2007 04:07 PM

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MattJen
Elite Veteran
Location: UK

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I am mixing the 5% which is recommended, and i am using the same oil that Chopperjockey told me to use, and he mixed it at 5%

As regards pumps no, we did not change a pump, we tried a wren pump in the Acrobatic, but it was not compatable with the JETCAT.

I am really surpised PeterRob has not come on board with is comments

Matt

12-07-2007 04:39 PM

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MattJen
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Location: UK

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Also

to add,
if there was aproblem with the lubrication ie not enough oil, or the wrong type of oil etc this would show up in the flight stats, which i downloaded and sent to JETCAT,

there was nothing unusual, no average high temp - which i would assume there would be if there was a lube problem,

Peter Wales' comments are interesting,

[quote]I really can not see how a stressed output shaft with plenty of gear backlash can cause the input shaft bearing to seize up.

without being synical, you wouldn't, cos if you did, you would have to supply an upgrade

The turbine will be coming back, and it will be in as new condition,
so it will be interesting now i have gone back to MObile JETOIL, as recommended by Dave wilshire it will be good to see how long the bearings last this time.

Matt

12-07-2007 04:49 PM

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chopper jockey
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Location: uk

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Matt,

I'm not sure how downloaded flight stats would reveal if not enough or the wrong type of oil was used?

It would not show a high temp if you had a lube problem, the temp probe only monitors the turbine outlet temp (TOT), which is not very dependent on the type or quantity of lube oil in the mix.

12-07-2007 05:05 PM

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MattJen
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Location: UK

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thanks Phil

I umderstand what you mean,

as said i am not decrying your product in anyway shape or form, i am trying to get to the bottom,of why 2 of my bearings fialed prematurely.

I really do hope all it is, is a lack of oil or the wrong oil used,
hence the reason i have gone back to Mobil jet oil which is what i was using on the pHT3,

Really time will tell, but i can only confirm this once the turbine comes back and do some flying again

Look forward to meeting up with you guys again next week

Matt

12-07-2007 05:11 PM

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chopper jockey
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Location: uk

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Are you going to bring some good weather with you?

12-07-2007 05:21 PM

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Got Jet Fuel? Turbine Helicopters > Maybe have got to the Bottom Of My JETCAT SPH5 Turbine problem -

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