Vettster

Hey guys... Im asking everyone with knowledge how to rebuild Turbines to help me with this project.

For starters.. Im not just some guy that picked up a cheap engine and wants to fly. I have 4 Turbine years under my belt and 3 working turbines.

I work as a Welder/Fitter so Im very mechanically inclined.

BUT! I have never attempted to do this kind of thing before and would appreciate all the help I can get.

2 years ago I was having fuel problems and I did manage to make it as far at to re and re the motor as far as taking the fuel wicks out and cleaning them. The engine has run since then..but the bearing are now making noise. I can hear a faint grinding noise and hear the ball bearing clicking over which says to me that one is missing.(I could be wrong) The last time I ran it...The engine was spooling up and all of a sudden she just locked up. This prompted me to shelf it. I now have to many planes and not enough engines, so I figured why not rebuild this one for my Sprint Jet.

The photos where as far as I got.

Whats next?

NUNU

http://www.youtube.com/watch?v=yeOt4z3rtio

This is a video I shot a while back..its a TJT eagle...same set up as yours... there is a part 2 also.

Vettster

Thanks Nunu...that should help me get it down to the bearings.

Vettster

Ok.. so Im down to the bearings. The rear ones actually feel pretty darn good and the shaft spins very freely without any grinding at all. The front ones on the other hand are very gritty.

The front bearings inner raceway fell out before I could observe which direction it sits on the shaft. From the pictures..could someone please tell me what is the correct way.

Does anyone know the type of bearing it is and where to get a replacement.

Do I have to remove the 4 screws holding the shaft tunnel on? There a SOB to get out. Can I leave the shaft tunnel on and just heat the hole thing and knock the raceway out.

Geoff_H

My Feedback: (2)

The 1st picture of the shaft with the lip of the inner race to the front is correct. Like wise the rear bearing should have the lip to the back. If they are GRW bearings the outer race will have a faint arrow etteched onto the outer diameter of the bigger race. The arrorws should face away from each other when installed on the shaft. The preload system forces the outer races towards the end of the shaft so the inner races need to have the lips away from each other to capture the balls. The compressor and turbine should force the inner race into the balls which will load the balls against the outer races and compress the preload. To install the balls cover them in vaseline put them into the outer race and then the inner race should press into the balls with a slight click and then turn free when fully installed. Clean the bearings and apply a little oil before installing. I think thats a kj66 engine and would have 608 bearings. The Grw 608 bearings have 11 balls. With all the balls installed there will be a slight gap just smaller then the diameter of a ball. They can make a clinking sound at low speed beacuse with no race to seperate the balls one can fall and fill the gap as they spin.

You should be able to leave the diffuser attached to the tunnel. The race should be very close but free fit in the tunnel for the preload to work. Am not sure it that engine uses coil spring or wave washers for preload and if it is front or rear preload.

Xicoy in spain is the best place I could find to get bearings. http://www.xicoy.com/catalog/index.php?cPath=1_7 Even with shipping and conversion they where cheaper then the others. They ship fast and the customer support is the best.

Geoff

Vettster

Thanks a ton Geoff.

The preload is a wave washer. But now I have to ask you what is the diff between front preload and back. How will this effect me and how should I do it.

Much appreciative of the link. That was my next question..lol

Trevor

Geoff_H

My Feedback: (2)

Front or rear preload refers to the location of the springs. If they are at the compressor end then it is front preload. The rotors are preloaded so the spring is moving the bearing in the direction that the rotor is trying to go with the most force. On my 1st turbine the rotor wants to go aft at low rpm and at about 75k rpm and above the compressor trys to move the entire rotor fowards. I blew up a front bearing and compressor while I was trouble shooting this. The rotor moved forward enough to overcome the rear preload and unloaded the balls in the front bearing races.

Geoff

Ruizmilton

My Feedback: (29)

Trevor:

You should be able to get the bearings from BocaBearings in Florida, for orientation, the thick outer race is the side that goes to the inside (should go first on the shaft) these are angular contact bearings, if you put them in incorrectly the shaft rotation will open the bearings

Vettster

Ok..Thanks for your help guys! I ordered the bearing from xicoy. Nothing to do now but wait.

So when its time to preload all this..(BTW..its a front preload) How much torque is enough.


I have to admit..I was a bit intimidated by these engines having not really worked on one before..but once you get into it..its just sooo simple. Im sure there are many things I could have screwed up.. but with you guys helping, it pretty simple isnt it..lol

Thanks for your help guys!

Trevor

Ruizmilton

My Feedback: (29)

Trevor:

Did you mark your shaft, compressor and turbine wheel for location index? if not, once you assemble it back you should have the turbine balanced to avoid damaging vibrations. The shaft has travel limits for the bearings, tightening torque has no effect on pre-loading, while I cannot tell you what is the correct tightening torque, every time I assembled an engine I used my own feel about what should be enough torque to ensure that the nuts do not come loose at high RPM.

Geoff_H

My Feedback: (2)

I dont have an exact torque. With the shaft in the lathe chuck I put the turbine on first and fairly tight by hand. The left hand threads should become tighter against the rotation of the rotor. You can use a T-socket or T-bar to reduce the bending force put on the shaft.

The engines in principal are simple but the devil is in the details.

Geoff

jason

My Feedback: (1)

Vettster

I have a Ram750 in bits here at the moment.

To get the preload working I needed to fit new O rings as the originals seemed to have swelled which stopped the bearing from returning forward when push back against the wavy washer, just some else to check while you have it in bits.

I found the inner wrap of the chamber had almost almost eroded away to nothing allowing the tunnel to heat up. This caused the rear bearing to fail due to the lube burning on the hot tunnel before it got to the bearing. Again worth a check.

I ended up buying a few 12 stick chambers so if you need one contact me.

When it goes back together you will need to balance the shaft with the wheel first, then with the compressor on with the same torque as it will be when assembled in the engine. Mine has some original factory marks on the nut and compressor which when lined up puts the compressor in the same radial position as it came off. You will need to use the rocking method to balance it and with a little persistence you can get very good results.

Found this link which describes how to balance it [link]http://www.jmaireland.com/hand%20static%20balancing.pdf[/link]

Jason

Vettster

Ruizmilton... I did mark everything to make sure that they go back the same way. But I did not mare the rear fan in relation with the Compressor[]

Geoff... I see the devil is knocking.. Good tip about using T bars.. makes sense. Will do.

Thanks Jason.. At First glance everything seems to be in pretty pristein condition. Ill double check though.

I will also take a look for those marks you have mentioned. Hope their there.. Sure would make things easier. Will also check the wave washer.

Thanks guys

Vettster

Jason..i never removed the Wheel from the shaft. No need as the rear bearing are good. So at least Im that far ahead of the game.

Vettster

Ok... The Burner can looks 100% ok. I pulled the outer raceway out without to much trouble. The Wave washer was by no means jammed at all, so thats good. I found the arrows on the bearing, so Im getting a better understanding of how they work.

Only problem is..there was no alignment marks for the compressor to match with the rear wheel[]

Guess Im going to have to balance that myself.

Thanks for the link Jason.. That will be a big help.

Trevor

Vettster

I had to tap into my EDF experience to balance the shaft but got her done.

I leveled a level and then added a bar of styrene that was polished as smooth as glass. Since I never removed the wheel from the shaft, really all I had to do was match the compressor to the wheel, and since the compressor is already balanced, it wasnt that hard to do. I got is so that no matter what fin is pointed up, the shaft will not rotate.

RCISFUN

My Feedback: (44)

Trevor,
When I first got into Turbines my first Turbine was a used RAM 500 which worked great for the first 50 flights, then it started with problems, like you I had never had a Turbine opened up and was intimidated by the mystical complexities of it....

But then I said what the heck, it’s an obsolete engine, why not tear into it.

I am glad I did as it was an educational experience and now I know what makes the Turbine tick!

On the RAM 500 the preload was set with shim washers, I believe that the 750 is also set with shim washers.

I took a photo of my 500 when taking it apart

Good luck on you re-assembly

Vettster

Thanks Rich. Yes I have all the shims ready for re-installation. Just waiting on the Bearing to arrive now.

Trev

BobbyMcGee

You realize that you are saving yourself about $800.00 by doing this!

So much for the "need" to send it back to the factory, huh!

Good job!!

Geoff_H

My Feedback: (2)

Somthing to try if the compressor is a tight fit on the shaft is to warm it up with a heat gun. Get it to the point you can just hold onto it with a bare hand and it will slide on or off no problem.

Geoff

Vettster

Yes Bob. That was the idea The last time I sent this motor in, it cost a fortune. Well about $800 Hardly worth spending that kind of money on a motor thats only worth well...about $800

Geoff..thats a good tip for those who may do work on their own in the future. Mine was a perfect fit. Not to tight and not to loose..(insert jokes here)

I just painted the casing. I picked up some header paint good for 1020C Its not just your regular spray on header paint that you watch burn off when you start the engine .lol This paint has a whole process. First you bake it in the oven at 250F and then 400F and finally 600F. Looks much better now.[8D]

TimD.

My Feedback: (207)

Excellent thread for DIY.

I have an old Ram 500 that needs the bearings replaced but havent due to what the cost is. I would like to fix it, anyone done this themselves and any tips ??

Tim

Geoff_H

My Feedback: (2)

Vettster Is the case stainless, aluminium or steel?

Geoff

Vettster

Start at the first post Tim...Its all here

Vettster

Its in the oven right now Geoff... but my money is on Steel