Garrett GT6041 powered kart

[smithy]

Thanks for the kind wishes guys, I'll still be in close contact with John so he'll still have his fingers in things and I'll be asking questions as usual.

To be honest, there's not much work to do to the "Green Beast" GT6041 kart, mostly cosmetic, the seat requires mounting, a little bodywork to the front fairing and getting the A/B to sing nicely. I'll hopefully be able to spend a little time on it in the next few weekends......It's amazing how much our regular work gets in the way of our hobbies, is it not?..!

I'm even thinking of fitting an electric start to it using a brushless motor, I'm very surprised at how little torque is required to spin the rotor when the cold oil pressure is ~70psi. A quick flick of a finger gives several easy turns.

I'd like to make the engine "startable" from the drivers seat if possible, John has made things quite simple yet elegant in it's design and I believe it shouldn't be too hard to do.

Cheers,
Smithy.

[stoffe64]

perfect Smithy!
you came up with a fantastic name for that "beast"
cheers/stephan

[racket]

Hi Smithy

Heh heh , having seen "inside" your 1/4 scale afterburning jet dragster and the degree of sophistication needed to have it operate at the levels it does , I can't wait to see what you'll be doing with the kart ................I'm excited :-)

It looks like the 6041 has the more modern "floating/balanced" thrust bearing www.turbomaster.info/despieces_garrett/731377-0001.php that produces less drag at start of spoolup than the "one sided" TV94 thrust bearing we used in the 10/98 engine , so should be a reasonable candidate for an electric start system , the "bull nosed" comp hub is just asking to be used for a "micro style" starter to lock onto , ....... using that big electric motor in your "speed machine" maybe ??

Cheers
John

[Johansson]

So the 6041 only has a 270° thrust bearing and it still survives?

Do you by chance know the shaft diameter where the bearing sits? It would be interesting to know if it can be used on the TV94 rotor without any heavier modifications, there will most certainly be a 02 version of the JU engine and electrical start would be nice to have.

[racket]

Hi Anders

The thread in the back of the comp is 1/2" left hand , I'd imagine that the rotating parts of the thrust bearing would have a 1/2" bore whereas our TV94 turb shaft quill is only 7/16" dia :-( ..........a precision bush maybe ??

It'd be a better arrangement than our current thrust bearing , with all its side loads from the lube pressure ....................is your setup as stiff to turn as the 10/98 engine was with lube pressure ??

Cheers
John

[Johansson]

Not impossible to make such a bush, how large is the thrust area compared to the TV94 bearing?

My JU-01 gets very difficult to turn with oil pressure over the bearings, it is even noticable with 200bar impingement where the shaft slowly starts to rotate and picks up speed the faster the shaft is revving.

It should be possible to source a similar bearing with the right hole diameter for the shaft, I might need to do some research.

[racket]

Hi Anders

Don't know very much about the 6041 thrust bearing size but you might be able to get an idea from here www.worldturbocharger.com/Product.asp?BigClassName=REPAIR%20KITS the 6041 is a "heavy duty" turbo so you'd imagine it would have a decent sized thrust bearing

It might be possible to configure our TV94 thrust bearing with pressure lube coming in from the bush bearing side to help "balance" the lube force .

Cheers
John

[Johansson]

It should be possible to make a sandwich type rear thrust bearing where an extra oil passage is made into the side of it with holes similar to the front bearing in the side facing forward.

The problem would be that the front brass bearing would have to be moved backwards a couple of mm´s to make room for it, no idea what that would do to the rotor dynamics.

[racket]

Hi Anders

Mmmm , probably best not to change the rotor dynamics , whats your thoughts on modifying the original "thrust washer" on the bearing side to provide some balancing force ??

I don't have bearing parts here to look at , sent them all off with the 10/98 engine :-(

Cheers
John

[Johansson]

You mean by drilling lube holes through it?

I don´t know if there is any oil pressure to speak of between the rear thrust washer and the front brass bearing, and the star shaped slots in it that feeds oil to the rotating part of the bearing should already route all the oil there is to the bearing.

Difficult thing to better something made by Garrett engineers.

[racket]

Yeh , there'd be lots of unknowns :-(

[Johansson]

Guess I´ll have to live with impingement starting as long as I play with the TV94 rotor, it works fine so I am the last to complain.

[racket]

Hi Anders

Yeh , theres some tradeoffs with using the TV94 bits , but their cost helps to ease the pain :-)

Cheers
John

[Johansson]

Is there any reasonable priced level above the GT rotary parts or is it the end of the line for us broke bastards?

I have seen Allison 250 radial comps for sale but it would be difficult to find a single stage turbine that matches it, perhaps best to not even think the thought....

[racket]

Hi Anders

Theres not a lot of choice between turbo sized and fairly large commercial GT units , I've looked all over the place for something in the 3-4 lbs/sec range but not a lot around.

I have considered the something in the 6 lbs/sec range like the first stage comp off the TPE331 engine , just looks like an overgrown turbo comp , the TPE has 3 turb stages so the second stage to drive the comp and the third for a freepower , but once we start to get into these sizes its probably easier to purchased an old engine .

For a bike you'd be better off using two of your current engines, they'd be smaller and lighter than a larger engine , just need a large freepower , lots of those around :-)

Cheers
John