frema

found an other adress for bearings .
these are full ceramic.
http://www.vxb.com/page/bearings/PROD/Kit7781

frema

just heard these bearings are not suiteble for turbines.

frema

Hi There.
I have now cageless bearings in my sophia .
but i can tell you all , its very hard to take the vibration out of the engine.
i noticed that the shaft tunnel is not in line ,and that makes it very difficult to balance it .
the shaft tunnel is made out two separate parts , and thats the problem.

But now the positive part, it runs much better.
the anoying sound of the cages at low rpm is gone [sm=teeth_smile.gif], and also the vibration is much less then before.
i think i succeed in it ,but i still need to run more with it.
It is not a matter of just putting new bearings in , no you have to change a lot before you can run it , but in my opinion its the only way , and cheapest way.
here are some pictures of the changed parts ,and one of the sophia after the last run .

Regards,

Martin.

frema

here is the link for the bearings.
They are from JM PRECISION.

http://www.jmprecision.co.uk/shoppin...&=SID#MOREINFO

F86_SABRE

Good to know.....thank you!

Reuben

frema

well Finaly i did it , the sophia is now running on cageless bearings.
i have to tell you all that the JM precision bearings where not suiteble for the sophia.
they are great bearings , but there is to much noise from them when i ran with the sophia, and also when you spun the turbine ,you heard balls tikking in the bearings, even with high preload.
i did my best ,but i just couldnt get it right , and if you wanna know , i spent a lot of time running and testing with it.
i even tryed different preloads , and tryed to aline the bearings ,but it was no use , there was a lot of vibration .
I balanced it very good , you did not feel anything when i spun up the engine over 10.000 rpm, but after the run , it was very bad.

But what i did was the following :
i took the old bearings ,and delete the brass rings .
there are 10 balls in the bearings , and i needed 2 more.
so i notice the balls are the same as the 608 ceramic bearings.
so i put the balls back, and made the bearing without the cage , and add 2 balls more in it (12 )
when i attached the shaft and compressor ,i notice the difference inmediatly.
No balls falling or tikking , and very nice running,even with less preload
also the balancing was a lot more easy to do.
i have to tell you , there will always be vibration in the engine , because there are more parts that runs with the shaft , you cant get out .
but you can make it almost perfect.
today i ran with it , and the engine is like new.
the starting is good , the acceleration is quicker , and the temp is lower.
I think i will leave it this way.
i also found another pump for it , but i have to test it first .

Regards,

Martin.

John Casey

My Feedback: (4)

Would that be the oil pump or the fuel pump?
And I would like to thank you for all your R&D work
on finding the right bearings and bearing modifications(add 2) to help make
keeping these fine fuel sipping engines running and operational.

frema

Oh sorry ,i didnt told you that, but its the feulpump.
i will search for a suiteble oilpump as well.

frema

Today i tested the sophia again.
de results where very good.
with an outside temp of 15 deg , the combuster worked very well .
yesterday i ran with no more then 5 % panel whipe , and that also worked, only the starting was a little more difficult , but no high temps.
i also did a test with the oilpump.
i wanted to run on half oil and half kerosine , but the pump stopped pumping( to thin) so that doesnt work.

when i have time i will make a few video's of the sophia running.

i also will show how i balans the engine.

Regards,

Martin.

gmwelch

I just had to reply on the subject of the Sophia J850 as I too own one. I have been following this forum for some time now and have just recently been able to get my j850 running again partly due to the valuable information contained here. My j850 also had poor starting issues and I have been succesful in correctiong the problem. There is so little info about these engines that thanks to the forums I don't know how I would have fixed it. The j850 I have is now converted to electric motor full auto start. The bearings are lubricated via fuel feed with approx 5% bled off. I am running the engine on 50%coleman 50% Kero and 5% turbine oil. The starting issues were corrected by repairing the leaking fuel ring and although I have not added any new holes to the combustor, I did angle a single ring of holes to increase the swirl. I had to make some changes to pump settings to accommodate the electric motor starting. The starting and running temps are almost identical to the air start version except I no longer have tobe a Scuba diver too.I so far have 2 extremely successful full runs on this engine so far and planning to run it againmaybe this week. I hope to shoot a video of this engine running at this time.If any one is interestedI would be happy to share this info in this forum. I will try topost some still shots also.

Thanks again for the information,

Gary

F86_SABRE

Hello Gary,
It would be nice to find out how you managed to convert it to full auto start. Did you change the ECU as well?

Regards

Reuben

gmwelch

Reuben,

I am still using the origional ecu as supplied from Sophia. The Jet-Tronic ecu ver 2.01b. This ecu already does support full auto start you just have to turn it on. The connector that goes from the ecu to the engine that turns on the glow plug is where you can attach the wire to run the motor. On the connector the middle connection is used for the glow plug, one end connection is used for common and the oppisiteend connectionis the motor. I then made a bendix to fit a Graupner speed 300 motor and fabricated the mount from ply, balsa and aluminum. I will try to get some pics posted when I get some time. For the ecu, you have to be in boss mode to make the changes. under the "basic menu" the is a menu selection for " protected startup" I changed this to "sequence". when you do this additional menu selections will appear in the "basic menu" settings such as "a-starter" , "a-starter2", "m-starter" and "start ramp dn". I am using "m-starter" right now set to 4.0 and "start ramp dn" set to 1.000. All this has been done through experimentation as I have no doc's on these settings. I stil am not sure what "start ramp dn" means. If this is a time setting, voltage setting or rpm setting?? I think it is an rpm setting. Also I enabled the start temp checking. I have experimented with the "a-starter" but could not get that function to work properly. One other thing, this ecu also now supports cool down after the run. I have set "cool down min rpm to 4000 and "cool down max" to 7000 rpm. I am at work right now and writing this down from memory so there may be some typo errors. Let me know if this helps or you need more info.


Gary

gmwelch

Reuben,

Here are some pics

Gary

F86_SABRE

Thanks for the information Gary. Unfortunately I had removed the engine from the plane and packed it away until I have some time to play with it around. I would very much love to see what alterations have been made to the internals to do away with the oil pump as that could be an issue with the engine should the oil pump hiccups.
Thanks again.

Reuben

gmwelch

Reuben

Here is a pic of the oil distribution system. The manifold which contains the 2 capillary tubes have been constructed from 1/32" K&S Brass tube with steel rods inserted into them. the steel rods are about .1mm smaller than the internal diameter of the capillary. the length of the steel rods is about 16mm. This gives approx 5% to6% bleed off between the 2 capillarys. I constructed this system based on Kurt Schrecklings book "The Model Turbo Prop" I had to make some adjustments to fit the whole system inside the blue cover. It is important to calibrate this system to ensure proper lubrication. Basically the system is calibrated at 1bar manifold pressure then comparing the weights of fuel quantity compared to weight of fuel bled off. You can adjust the length of the steel rods to give more or less fuel/oil mix. The steel rods are tapered on the ends so that when they are forced against the loops in the capillary tubes they dont plug the output. Let me know if this helps or if you need more clarification.

Gary

F86_SABRE

Hello Gary,
Thanks for the information. I will have to discuss the matter with an engineer friend in order to see whether we can make the necessary modifications. Unfortunately, I do not have the capacity to make such alterations myself. However I may have the brass and steel rod in my garage so it may not be all that difficult (theoretically at least!!!)
Thanks again Gary
Reuben

gmwelch

Reuben,

As I had promised. I have posted a video of my Sophia J850 running on youtube.

http://youtu.be/nM7yV8hvXSo Gary

F86_SABRE

Hi Gary,
That is most impressive. The start-up transmission is excellent. I am VERY impressed! Unfortunately my friend does not have the time to do any work on the engine so for the time being so I have to stay put. We will see what will happen in the future. Thanks for the video. Impressive indeed!

dribbe

Like the Vid... always loved the start of the ophia! I think I still have two normal J850's... and one engine core mounted on and experimental Sophia helicopter... Have not run them in some years.... but am fond of the engine... Nothing had the fuel economy vs thrust of the Sophia.... This one was written off... met a bad end in my balsa Bandit.... asphalt about 260mph...


David

F86_SABRE

Hi Gary, are you still using the 50% Coleman fuel in the fuel mix with the new set-up?
Reuben

F86_SABRE

Dave, pity on that turbine. After a stripdown wasn't there anything salvageable? Of all the turbines I have I still really love the Sophia sound and wish to maintain it as far as possible. Gary's results are really wonderful as it helps saving a bit of carrying weight around!
Reuben.

gmwelch

Reuben, For the run in the video I had 60% Coleman with 40% Kero and 5% oil, I believe that 50/50 would work fine, But I had just installed new flame fences (Made from Inconel wire to replace the oem burnt fences) and the air temp was getting cooler outside. However since Coleman is actually less cost per gallon than Kero (unless you by 5 gal or more of Kero) then running more Coleman than Kero is Thriftier. The Sophia's seem to like Coleman fuel alot. I did have problems with the origional starter motor I was using in that it was a Graupner speed 300 6V motor and one of the brush holders broke off rendering the motor useless. The Graupner speed 300 6V motor is no longer available so I struggled for a replacement. I found an excellent replacement at Tower Hobbies, the T-370 Motor. It is the same size as the speed 300 but can operate to 9V instead of 6V and since I am using a 7cell Nicad pack It works out very well. By the way these motors sell for about 9 bucks.

Gary

F86_SABRE

Gary if you have not located a Graupner 300, I just purchased one from GLIDERS Distributions, here:
http://www.gliders.uk.com/prodinfo.asp?number=G3306
I understand that the Graupner 300 is a re-badged Mabuchi RK-370 motor.

Reuben

dribbe

I stripped it down... virtually every part was fatally damaged.... Was a rattle can....
My engines are US/Japan spec... I ran one of them in my Silver Mig for 6 years... never came out of the aircraft... zero maintenance.

David

F86_SABRE

That's bad Dave. Sorry for the mishap
I can imagine on its reliability. Very difficult to throw a blade I suppose. I bought mine from Germany. For now its still runnning although I hibernated it until I can get it convert it to auto start. I do not wish to render it a door stopper.

Reuben