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HomeTurbine✈️Aircraft🚁HelicopterTurbine Helicopters › Anyone seen inside a Jetcat SPH5 gearbox???
08-23-2008 09:01 AM  12 years ago
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Sparkhead

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Melbourne Australia

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Anyone seen inside a Jetcat SPH5 gearbox???
I was looking at a few pictures of the different setups for the SPH5 turbine and noticed that some support the end of the shaft in a bearing and some don't. I just wanted to know if anyone has seen the inside of the right angle gearbox so see what bearing support is in there. Is there 2 bearings next to each other or more preferably is there a bearing at the top and the bottom to give really good support.

Hopefully someone has been a little more adventurous than me and had one apart.

Mick.

Robbe & Futaba.
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08-23-2008 09:47 AM  12 years ago
MattJen

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UK

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in the SPH5 that i had, there is just one big bearing at the base of the gear box for which the shaft goes into,and at the top of the cone/gear box lid there is a smaller bearing..

the end of the output shaft does not come with a bearing at the top, the support depends on what conversion you are using..

On the hobbyparts acrobatic conversion there is no bearing support as of yet, they did talk about making one, my only conccern with this is you end up putting a lot of side load on the output shaft as it utlises belts, so as you add pitch, and loop and roll ( which i never did) you really do add stress on that shaft..as the base plate can be seen flexing at extreme manouvers.

I had a premature failiure of that bearing, and it was sent back to Jetcat and they picked up on no support, but they still replaced the entire gear box under warranty, the new gear box has a very big bearing.

My opinion, on some of the conversions,the gear box output is is supported, so there is no side load forced upon it. On the predator it utlises the existing start shaft, so it is all kept 90o,which i like. I have seen a picture with the SPH5 being used..

There other conversions but i only know the acrobatic and zelouse..

Matt
All The Best
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08-23-2008 04:30 PM  12 years ago
Sparkhead

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Melbourne Australia

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Thanks Matt,

So there is a bearing in the base of the gearbox and then the black ring around where the shaft pops out the top must just be a seal? It'd be really nice if they could get a bearing in there to support the top of the shaft and keep the gear mesh nice and smooth. I was never 100% happy with the noise that came from my gearbox but it seemed to be working alright. I have installed it in a frame again and it still seems alright but I can change the noise of the gear mesh with different angles.

I'd love to see some pictures of the inside.

Mick.

Robbe & Futaba.
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08-24-2008 10:24 AM  12 years ago
MattJen

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UK

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So there is a bearing in the base of the gearbox and then the black ring around where the shaft pops out the top must just be a seal? It'd be really nice if they could get a bearing in there to support the top of the shaft and keep the gear mesh nice and smooth

Sorry mick, i misread your post,or gave you the wrong impression,

at the base of the gear box there is a large bearing, as the shaft protrudes through the gear box lid / cone, it goes through another bearing although smaller,

it is the actual end of the output shaft that you can see is unsupported... and this supports depends on what conversion you are using...

Sorry about that!

Matt
All The Best
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08-24-2008 12:26 PM  12 years ago
chopper jockey

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The SPH5 gearbox has two "chunky" bearings supporting the output shaft. The top one even "chunkier" than the bottom one. They are not ceramic. With regards to the hobbyparts conversion, you do not need to pull the drive belt so tight that you over stress the bearing, just tight enough to stop the toothed belt from jumping.
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08-24-2008 12:35 PM  12 years ago
Sparkhead

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Melbourne Australia

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Ah thanks guys, so there are 2 bearings. One at the very bottom of the shaft inside the gearbox and another at the top of the gearbox which is the black ring you can see. It seems strange that I could load up the gear mesh in that case considering the bearings are at the 2 extremes of the housing.
Mick.

Robbe & Futaba.
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08-24-2008 12:47 PM  12 years ago
chopper jockey

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The top bearing is huge and should easily take the required side load. The bottom bearing does not need to be so heavy, as it is just there to support the shaft.
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08-24-2008 02:35 PM  12 years ago
MattJen

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Phil

can u post a photo ?

Matt
All The Best
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08-24-2008 06:12 PM  12 years ago
chopper jockey

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Matt,
Hi, although I have one here in a box, it's not mine and I do not want to open the lid until the new owner says it's ok to do so. But you can tell by looking at the outer shape just how much chunkier the top bearing is.
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08-27-2008 10:46 PM  12 years ago
MattJen

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things must of changed, i did have the older version gear box, prior to sending mine back after the bearing failed..

mine were ceramic at the time, although i could have been mistaken..

The wrens if i recall when i opend up the gear box to see if it had been lubed were ceramic. and they were rock hard, we took one spare ceramic bearing apart it was a tiny spare one, and we hit the ball with a metal hammer, the ball pushed into the hammer head, no matter how hard we hit it we could not damage it...

Ross was showing me the differences between the two types metal and ceramic..

Matt
All The Best
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08-27-2008 11:24 PM  12 years ago
chopper jockey

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uk

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Matt,
Ceramic bearings are used on the input shaft, which is turning very fast and runs at a high temperature. The output shaft has a lot of torque on it and turns somewhat slower and does not get hot, so no ceramic bearings are required on the output shaft.
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08-28-2008 12:30 AM  12 years ago
helibeli

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wales.uk

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ceramic bearings
With these ceramic bearings,are the cages made of ceramic material as well(silicon nitride i believe)? I've seen the balls advertised on an american site from about 70 pence each.
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09-07-2008 09:42 PM  12 years ago
Coolrunnin

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Manchester U.K.

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The ceramics used in high rpm applications like model turbine shafts are cageless from what I have seen.

I have used caged hybrid ceramic bearings in piston engines however (steel races with ceramic balls) and these used steel cages rather than plastic or ceramic.
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