Garrett GT6041 powered kart

[smithy]

Hey All,
As promised, I've uploaded a vid to Youtube to show the new electric starter "Mock-up" mounting system on the big 6041. As you can see, the Castle 1717 1580kv motor turns it easily.

www.youtube.com/watch?v=qi47QKtXKk8

Mark, the 1717 is substantially larger than the 2650kv motor you have, it's 50mm dia and has some serious torque. Your 2650kv motor should turn your T30 ok though but it will be marginal.

Cheers,
Smithy.

[Johansson]

Good job there Smithy with the starter, it connects really smooth and should have it running in no time once you start feeding her some diesel.

[racket]

Hi Mark

The GT 60 has a "balanced" thrust bearing , so much freer running than the "unidirectional" TV94 thrust bearing that the 2650Kv motor was trying to turn , .........is the T30 thrust bearing a modern "balanced" one ??

Cheers
John

[racket]

Hi Smithy

BLOODY BEAUTIFUL :-)

What else can I say "Dr Doolittle " , she's going to be a sophisticated lady by the time you're finished with her .

Such sweet acceleration of the rotor , I love it .

Cheers
John

[racket]

Hi Mark

I'll PM you some info on working out torque for "Kv " motors

Cheers
John

[pitciblackscotland]

Hi Smithy,
Awesome work mate I think you might get a lot of people interested in your set up and how you machine up that bendix clutch. I was going to scale up one two i got types of bendix clutches see pics the one on the right has a spring inside it but other than that they are basically the same. I may not use it for the t30 having seconds
thoughts on it. I'll stick with the leaf blower for now.

Cheers,
Mark

Attachments:

[pitciblackscotland]

Pic # 2

Attachments:

[turbochris]

are you using vton o-rings? think a silicon o-ring would work better? They're pretty tough and the ones i have seem like they have a little more "traction"

[smithy]

Dec 23, 2011 17:06:46 GMT -5 turbochris said:

are you using vton o-rings? think a silicon o-ring would work better? They're pretty tough and the ones i have seem like they have a little more "traction"

Hi Chris,

Yes, I'm using Viton "O" rings but I'm having a little drama with the compressor nut itself, there is a "balancing" cut-out on one side of the leading edge and it is causing the bendix drive to sit a little off-centre and hence there's a little vibration.... so I'm not happy with that aspect and am experimenting with some different "O" ring sizes etc...to try and eliminate the vibes.

I don't seem to have any problem with traction of the "O" ring on the nut, the bendix pushes harder as more torque is applied.

Cheers,
Smithy.

[wolfdragon]

what about a screw on rubber foot? then you can just bump on the center and not have the unbalanced engagement

[smithy]

Dec 27, 2011 17:29:57 GMT -5 wolfdragon said:

what about a screw on rubber foot? then you can just bump on the center and not have the unbalanced engagement

Hey Wolf,
That would be nice but the GT6041 doesn't have a "screw on nut" as such..... the "nut" is actually part of the impeller, it's a solid "boreless" impeller and the turbine quill screws into the rear side of the impeller, very strong and rugged indeed. 1/2" LH thread if I remember correctly.

Cheers,
Smithy.

[wolfdragon]

yeah but if the bendix were to advance a rubber cone or cylinder rather than the o-ring, wouldn't that get around the balance cuts?

something like these: www.mcmaster.com/#threaded-sundry-bumpers/=fjuhq3

[smithy]

Dec 27, 2011 19:41:00 GMT -5 wolfdragon said:

yeah but if the bendix were to advance a rubber cone or cylinder rather than the o-ring, wouldn't that get around the balance cuts?

something like these: www.mcmaster.com/#threaded-sundry-bumpers/=fjuhq3

Yes Wolf, that could possibly work, I might investigate more...thankyou..!

Smithy.

[ashpowers]

Forgive me for the simple observation, but doesn't a bendix assmebly make things more complicated? If you were putting this on an aircraft and needed a completely hands-free startup mechanism I can see reason, but in this case wouldn't it be easier to put a socket on the end of the starter shaft which matches the integral comp nut and mount the starter on a push-slide mechanism to engage it by hand - using a return spring to pull the starter back when you release it? You could even automate this arrangement and use a dampened solenoid to actuate the starter. With just a little bit of carbide burr massaging of the starter's socket you can profile it such that there will never be an engagement bind.

Relying on a bendix assembly requires torque to be applied to the mechanism in order for it to extend and engage, which requires you to use a soft engagement material to prevent significant wear on the comp wheel's nut. The low durometer you'll have to use to prevent damage will inherently create instabilities..... especially with the spherical profile the front of that nut has...

That's a nice bendix assembly you've made and I know you have a good bit of time in it. Only other alternative I can see is to machine the end of compressor nut to a conical profile and machine a matching rubber cone insert for your bendix. A conical shape vs. spherical shape will self-center and eliminate the positive feedback de-centering.


...... /ramble off

[racket]

Hi Ash

I was down at Smithy's place on Friday discussing the starter and it looks like the next approach is to do what Luc did with his start system ( PJ Site > Forum > gas turbines > My Turbine ( GT4708R) ) and machine a tapered bore in the bull nosed snout of the comp wheel for the bendix to engage the O'rings into , this won't disturb the balance machining on the comp snout thats currently causing the problems , also with 2 Orings there will be even more self alignment .

Smithy has a huge amount of experience with micro turbine starters of all sizes so will get this one sorted without too much trouble , the end result should be a kart that can be started with the driver in the seat :-) ....................can't wait to hear that big girl spoolup without the noise of a two stroke blower in the background .

Cheers
John