For Sale: J-85 PRICED REDUCED TO $7,500

[ernie wrenn]

Engine is in excellent condition and is complete less tail pipe. spins nice and smooth and includes side doors with actuation mech.

Includes complete EGT leads for tail pipe.

Stored indoors only.

No paperwork and no FAA cert. This is a ground pounder for your next project.

Will pallet and wrap at no charge... freight is on you.

$15,000 obo.... NOW $7,500 WIH EXTRA PARTS. Extra Bishops hat and tail pipe.

Ernie
803-442-9206

[cnctech]

HI ERINE JUST WONDERING IF YOU MIGHT HAVE A PART AND SERVICE MANUAL FOR A ORENDA J85-CAN-40 . ( OVERHAULED BUY BRISTOL AEROSPACE IN 1969 ENGINE HAS A TAG THAT STATES DO NOT USE ON TUDOR FOR DRONE USE ONLY ) NOT FOR EXPORT. LEN

[turbochris]

Drone motor? There's a version of the j85 thats used on missiles I hear they like to blow apart after a few hours..... If the warhead doesn't kill it.

[ernie wrenn]

That myth was debunked several years ago. Basically 2 types of J-85..... with starter or air start. The air start can be switched over by adding the starer to the gear box.

Sorry no manuals.. I'll check around, I know several people with 85's.

ernie

[cnitrofumes]

Hi Ernie..I was told the J85-7 was a non afterburning version built for drones only. I was also told the -7 could not be used with an afterburner whether factory or custom built as they had a lighter duty turbine section and can't take the heat....
Thanks

[cnitrofumes]

Ernie I'm assuming your "debunked" comment meant this info on the -7 is incorrect... thanks

[finiteparts]

Hi cnitrofumes,

That is not true. The turbine is not "lighter duty" (except for the 1st stage blades size ((due to the higher mass flow of the -5), J85-GE-5/5A are the same and they run afterburners) and the addition of an afterburner doesn't cause the turbine to operate at a higher temperature if you are controlling to T5 (EGT). The problem is that the -7 was built for the GAM-72 and the Firebee applications. Due to the lack of an original afterburner, there is no T5 amplifier like you would see on the manned versions of the engine. The T5 amplifier compares the target EGT to what it is seeing averaged by the EGT probe assembly and amplifies the error to move the variable exhaust nozzle open or closed. Changing the exhaust nozzle area changes the pressure ratio across the turbine section and thus the EGT,flow function, compressor op line, etc., etc..

So here is where you run into issues...most people making their own afterburners are making a fixed area nozzle. If the nozzle cross sectional area is too small, then the pressure ratio across the turbine stage is reduced and the only way to get the power needed to drive the compressor is to increase the turbine inlet temperature. If this occurred and you had installed a set of EGT probes, you might not see an increase in EGT, but you are overtemping the 1st stage...likely causing it to let go. Now if you were not aware of the systems trades that you made by installing the afterburner on that engine, you might blame the turbine and say it is somehow "lighter-duty".

Now, I am not saying that the -7 is the same as running a "manned" version. There are some very specific issues with the -7 (or the -3). The first one is that people often say that you can add an electric starter to the gearbox, which is very inaccurate. The -7 has a dual pad gearbox that runs the oil pump on the aft side and the fuel control on the forward pad...that's it...there are no other free pads. So then, they say that you can just swap the gearbox from another manned J85 or CJ610 to get all the accessories you need. This one may be possible, but the mid-frames are completely different drawing numbers, which suggests that you can't just rotate the -7 midframe to position the gearbox at the bottom so that you can use the -5/etc or CJ610 gearboxes. If it was a simple rotation of the midframe, GE likely would have just made it a part difference in the same drawing, not an entirely new drawing (eg. the turbine blades for the -7 is a 634E579P1 while the -5/5A uses a 634E579P3...notice it is the same drawing number, just a different P number).

No big deal, right...just use the airstart system to start it. OK, the second big thing is that there are no records of hours or starts for most of these engines that end up for sale. These engines are lifed based on starts and time. The number of starts basically controls the low cycle fatigue life. The hours can control high cycle fatigue and creep lives. If you look at the -3 manuals for example, the starting EGT should be at 1195 F. IF you exceed this, then you are starting to get time limits on how long you can run over-temp'ed. So let's say that you have a leaky fuel injector and you get a hot spot such that your average EGT rises by 100 F to 1300 F. If you look at the table, you can only operate at that temperature for 16 seconds before you have to shut down. If you overtemp 10 times, your turbine has exceeded it'd design life and you need to replace the hot section parts.

So here's the question...if someone gets a used engine and adds an afterburner, they might not see the hot streak and try to crank the engine for 25 or 30 seconds. They don't realize that they just consumed a huge chunk of the turbine's stress-life. When they re-run the engine and it explodes, do you think they will blame themselves or the fact that it is a "drone" engine?

You have to remember that these -7( and -5's) engines were originally designed in 1957 and first ran in 1958. The turbine materials were not stellar and they need to be respected.

Feel free to contact me directly if you have any other -7 questions.

Thanks,

Chris

[cnitrofumes]

Chris ... thanks for the very in-depth description of the differences.
You are correct in assuming my homebuilt afterburner would be fixed nozzle.
It's kind of comical how an assumption ( lighter duty turbine ) can become "fact" once repeated enough times.
I guess the -7 is less desirable in the jet car applications due to air start only setup,the drives and oil tank being mounted to the top of the engine and the assumption they can't run an AB....
Thanks for the info....

[ctgspecialist]

Thank you for that write-up as well! It provided much needed information, I have been watching a J85-7 on eBay for over a year, but could never pull the trigger on buying it. Glad I didn't- it's not as easy as they make it out to be to put electric start on.

Spenser

[finiteparts]

Hi Spenser,

I am glad that I could help to illuminate some of the challenges with the -7 for you. I have two of those engines that I bought from the guy selling them on eBay. The good news is that the money I spent helped to support his museum. I think they are an excellent buy and the two engines that I have are in very good shape for their age. But, I did want people to be aware that they are not just something that you can slap into an old Pinto and go out annoying the neighbors with.

Now that being said...the aviation industry as a whole is moving to reclamation of the high cost alloys in the engines and as such, it will get harder and harder to find decent engines in the future...so that played into my decision making too.

My purpose for these engines is more historical preservation. I am hoping to get them restored to functional condition and run them for fun...these engines are a work of art. The guys designing these engines back in the late 1950s did the design by hand, no computer stress analysis, etc...and yet the J85 is still running in service aircraft today! I think it would be a real shame for today's generation to loose touch with what was done in the past and how elegantly the system design was achieved. That is why I have most of the engines that I do...the T700 engines are some of the most amazing engineering out there and it is no wonder the military loves that engine.

Thanks,

Chris

[turbochris]

i guess you better be right on top of that TIT when you go to run one of these.

[ctgspecialist]

Those are the exact engines I was referring to. I was looking at them for a possible jet car, but am leaning more towards a Boeing with a power turbine now.

Spenser

[jim2000]

Hi, I was just wondering on your J85, do you still have it?