Cool machine :-)

I wonder how much a splatered mosquito on the compressor puts it out of balbance in numbers [8D]

Sonnich,
I was thinking EXACTLY the same thing

Well with my Schenck I could probably measure that ....but little knicks on the compressor blades do make reasonable adjustments to the balance of up to 3 to 5 gram/mm. We balanced my Simjet 700 to .04 gram/mm on both ends just to see if it could be done...this was done by just scraping the dull casting on the compressor with a exacto blade to make it shiny a couple of scrapes at a time..this was measurable so that sort of measurement is actually achievable.

Mark Kyle

Hey Mark,
You're quite right, our old Schenck CAB-690 can do ridiculous measurements too. We do RR Allison C20 and C30 rotatives here and use 28mg/in as the spec. however, it's able to do dramatically better than that, as an experiment we tried to get it to zero, we found it's very difficult for the machine to measure this though, the spot seems to travel around the "dart board" like it's drunk when we use the 50mg scale, even when reasonably heavy trucks pass by our workshop the the poor thing goes nuts!!

Cheers,
Smithy.

Hi Brett

We dont see anything like that on the HT0B because it is all digital not analogue. The balancer has special software (dsp I would think) that can take all the noise from the bearings and any outside interference from affecting the measurements. As you can see on the pics our lowest scale is 5mg fsd. The mass that you guys are measuring is large but my balancer the max weight I can put in the balancer is 3kg. I am still amazed by how good it is. My mates at Qantas tell me they only use Schenck balancers and so do most of the airlines for all their turbine maintenance


Regards


Mark Kyle

Yes, would be nice to have the latest digital gear, but Rolls-Royce use the same machine we have to do their RR-250 stuff and swear by them.

We also have a Heinz FM-AP250 soft bed, but find it only good for larger tolerances and seems to never do the same thing twice!!

Cheers,
Smithy.

Hi Brett

Well that is always the big test to make sure that the machine is ok. We have done exactly that when I first got the balancer. Did a measurement then did it again a few times by taking the unit out and replacing it in the holder each time...and every time we put it back in it came up with the same measurements...then make a adjustment and sure enough that adjustment then changes the reading. Because this balancer can measure such fine tolerances it did take us a little while to start to trust its readings. But we did so many tests that it proved that it was super consistant and very accurate. I must say though that I will get it calibrated each year as per spec to make sure it maintains its accuracy. Don Baily at Schenck here in Australia is a very switched on guy and knows his stuff.

Regards


Mark Kyle

Mark, many many thanks for your postings, you have got me so interested I am wondering how much your service would cost on my three motors (JJ-1800 - PST - Wren 44) do you just do the balancing or full service, bearings and what not?

None are my motors are at the given 'service time' but I am interesting in giving them the service, I, as my name states am up in Taiwan.

Cheers.

Gw

Hi GW

Contact me off the forum for further as I dont like doing business on here just the tech talk and idea swapping as I dont think this sort of pricing is allowed in the rules...but maybe the moderator can tell me this you can email me [email protected] or [email protected] My website has some details on it http://www.kyle.com.au/Balancing/pricing.htm bearings are basically supplied at just a little over cost and I keep both sizes in stock all the time

Regards


Mark Kyle

Cheers Mark, will do!

Gw

Hey All,
Just letting all the Jet-Joe turbine owners out there know of a new website for sales, support and forum. It's based in Australia and we hope we can be of service to all JJ owners out there. The new website is owned and run by Rob Orrock. Please feel free to drop by and let us know about yourself and your engines, good, bad or indifferent.

If you're interested, go here: http://www.ausjets.com/

Cheers,
Smithy.

Hello Mark !

I´am a bit confused about the figures of unbalance.
You are talking of gr/mm in the text and I can read mg on the Cab720 display is this value mg/mm or what ??
You say you set a limit under 1 gr/mm as to balance all turbines.
But on the Cab 720 it show 0.85 to 0.76 mg/????

Please make this clear to me

Regards / Christer

Hi Christer

The display shows mg but the actual measurement is said as grams per mm...I dont know why maybe its a german thing...I asked the Schenck guy here about it and he basically said the same thing.... my balancer can go to .02grams per mm thats 2 hundreths of 1 gram per mm thats good enough for me.


Regards


Mark Kyle

Hello Mark !

I´am asking therefore I´am doing service to the Swedish Jet pilots turbine and i particular SimJet turbine. And have a great interest in balancing. I´ll do the balancing down to max 10mgr/mm all and under this is bonus if bearing condition is good .

Regards / Christer

Hi Christer

I can of course balance to those measurements easily as well but Simjet set the spec to be under 1gram/mm..Lars deems this to be the lowest level required for turbine balance and lets face it if you have the balancer capable to do this you know what I am talking about when I say even the slightest knick on the compressor will change this super low reading..we do a fine balance by scraping the dull metal on the compressor with a exacto blade to make is a shiney surface and this makes a big measurement when balacing at under 1 gram. My greatest reason for spending the amount of money to buy this particular Schenck was the ability to be able to core balance a engine. Doing a dumbell type of balance then taking the compressor off to reassemble the engine destroys the balance you just had. Core balancing is the only true way of balancing a turbine...when you have done it this way and done it the dumb bell way and can actually measure the major difference between both methods the core balance way is the only way to make sure the engine is balanced in a running mode. I dont know what type of balancer you have but all I can say from testing both methods of balancing quite a lot when we got the Schenck there is NO comparison between core and dumb bell balancing.

Regards


Mark Kyle

It's very important that you start and run the turbine several times before final balancing in order to let the components settle correctly and achieve a stable balance. This effectively precludes dumb-bell final balancing.

Best regards

vfr750r

You are correct about running the engine first. It does make a difference to the balance due to all the metal having to go through temperature shock and for the bearings in the shaft tunnel to settle etc. But this is usually only needed when you change bearings or from a brand new turbine. Simjet do the same thing at the factory. Once the engine is assembled from new it is balanced then test run then balanced again. From new the engine balance does change after the first run. There doesnt seem to be a lot of difference when doing this on a engine that has had a bit of running and you do a bearing change. But I can assure you that there is a big difference when you do a dumb bell balance and you take the compressor off to reassemble the engine. I would say 9 times out of 10 that you will have at least a 10 to 20 gram per mm difference from the original. There is no way you can get that compressor and nut in the exact same spot as it was when you did the dumbell balance. We can prove it and have done so many times. The only real way to get a good running balance is to core balance. Remember that before I got the Schenck we used to only do dumbell balancing. I can do both with the Schenck and also test and quantify the results between both methods. I am not trying to be a smarta*se at all and I might seem to be pontificating but I am not....as I have said previuosly after getting this balancer I found out a lot of misconceptions about balancing and I was surprised by the results, the difference is now we can actually see and measure the difference between both methods.

Regards

Mark Kyle

What type batteries are you guys using to power your fuel pump/ ECU? I have a JJ1800 that can only reach 105,000 rpms. I'm almost certain that it is the battery. I'm using an 8.4V 3000ma NiCad battery that is brand new. While the engine is running , full throttle voltage indicates 6.5V on the HDT. What are some of the readings you guys are getting while your engines(1800) are running. I have the Regal ECU and Flightworks fuel pump.
Thanks,
Steve

Hey Steve,
Which FlightWorks pump do you have? I assume the 400? My 1800 runs fine just using a 7.2v 4600mah battery and a slightly "modified" JJ pump. 6.5v at full throttle seems too high to me as mine rarely goes beyond 3.5v at full noise, be sure that all your plumbing is clean and clear and filters are clean, you may even have some blocked or partially blocked fuel nozzles restricting flow, hence the high voltage/current seen.
Do you have a flow regulator in the fuel line? The FADEC is trying to get the pump to deliver more fuel but it's just not getting through for some reason. Are you able to swap the pump with a known good one? A simple process of elimination may be required.

Cheers,
Smithy.

I have the 400. I'm going to check my lines again. I just got it back from JJ(Gabe). Gabe ran it and he told me that he was able to get it up to full rpms. They upgraded it with the new parts they have to make it run cooler. I believe they replaced the shaft tunnel and something else.
If your voltage is indicating 3.5V at full throttle, then there is something definitely wrong with my lines or maybe even the fuel pump. I'll try some more playing and I'll let you know. Thanks for all of your suggestions.
Steve

rumor is that JJ will be relising a 8lb turbine along with a 35 lb !!! and a smoke system[:-] dont know if its true


just imagine 800.00 for a small turbine and 1,200.00 for a 35lb

Steve,
Did Gabe use your pump or his own "test unit", It's not uncommon for the same type pump to display quite different voltages at the same engine rpms, I guess it all comes down to how "good" the pump itself is.
The later model 1800's all seem to run reasonably cool, temps in the mid 500's @ idle are the norm.

Cheers,
Smithy.

littlepiston, where did you read about the 8# turbine ? the 35# is mentioned on Gabe's site...

cant realy say....



i spoke to Mr. Brown the other day i will be picking up one of his turbine in about 3 weeks i live about 120miles away from him i think i will take a trip up there and visit his shop

I spoke to Joe ealier this month about larger turbines and he confirmed that have a 35 pound unit for release later this year.
Looking forward to it, as one of these will go nicely in a flight eagle jet..

Rob