"Fat Boy" 12/118 thrust engine

[madpatty]

Hi John,



After looking at the pics i am in a bit of doubt...maybe pics are not explaining to me that much...








How is the axial movement of the turbine shroud restricted.??



From what i have understood is:-



As the turbine shroud is bolted below the evaporator wall of the flametube......lets say if the turbine shroud wants to move axially towards the turbine end....It will exert a force on the evaporator wall through the bolts..



Now the evaporator wall(which will be welded to the outer flametube wall) wants to move forward which in return is restricted due to the inner wall of the inner flametube(which in turn exerts the force on NGV through those cuts on inner wall of inner flametube that are aligned with the NGV).





Now if you weld the Turbine shroud to the NGV then how will you disassemble the engine in future(because I think then you will not be able to take out the turbine and on firsthand how are you going to assemble the turbine after welding the shroud).



And the last thing is this setup all in a packed locked assemble without any need in the future to dissasseble it completely.



Cheers,

Patty

[racket]

Hi Patty

LOL...............its for me to know, and for you to work out ;-)

Theres no axial forces on anything , and it will be able to be disassembled.

Unfortunately its a rather "messy" solution compared to my previous engines , but thats R and D , I'd design things differently in future .............heh heh , I didn't do much design work at all on this engine, preferring to take the more "interesting" journey .

Cheers
John

[racket]

Hi Patty

If you have a look at the 10/98 engine build jetandturbineowners.proboards.com/thread/19/10-98-engine you'll understand the differences and how things go together.

Cheers
John

[madpatty]

Hi Racket,

Now till now i was thinking that the exhaust stub you welded to the NGV is acting as the turbine shroud(following the turbine blade geometry from inducer till exducer)

I am referring to this:-

postimg.org/image/e4yyb4szh/full/

But if it would have been acting as turbine shroud then you would NOT have been able to remove the turbine without removing the shroud.

So there must be something which i am missing.
I am missing the part which acts as the turbine shroud.(which is the last part in your assemble process i guess)

As this picture shows there is enough space between turbine and stub that turbine can be easily removed without removing anything else.

jetandturbineowners.proboards.com/attachment/download/16

Cheers,
Patty

[racket]

Hi Patty

You got it :-)

The turb exducer shroud , is at one end of the "jet pipe" , theres a flange welded to that "tube" , the flange is held in place against the end of the NGV exhaust stub with a Vband clamp , note the groove in the end of the exhaust stub on the NGV that the Vband fits into .

The NGV exhaust stub has an ID of ~130mm , the turb wheel has an inducer diameter of 129mm , so the turb and shaft slips into place with the NGV and flametube mounted to the shaft tunnel , the turbine shaft can be easily removed with minimal disassembly .

The flametube outer wall is only welded to the front wall , not to the back wall , there will be 6 "pins" holding the flametube in position in the rear endwall containing the evaporators , I'd prefer the flametube to be a complete unit , but have been forced to have its rear wall removable with the current design .

Cheers
John

[racket]

Hi Patty

Heres a pics of the flametube with the securing pins in place holding the outer wall to the rear wall .



When the engine is running the pressure difference between inside and outside the flametube will tend to force the outer wall into the rear wall rebate , the pins only need to hold it together until the engine is running .

Cheers
John

[madpatty]

Hi Racket,

This thing is perfect.

I dont know if it is the disassembly reason that you are following this route??

Once closely analyzing the pics i thought you can disassemble even if you have welded the external flametube.

Cheers,
Patty

[racket]

Hi Patty

LOL.......It'll do the job hopefully :-)

With my previous engines the rear wall is welded to the outer side wall and the entire flametube is fastened to the "front" of the NGV rear wall , but with this engine the removable rear wall is fastened to the rear of the NGV rear wall which leave a 4mm thick projection of the NGV wall inside the flametube rather than a flush fitting wall as previously,..........its untidy .

To be able to construct a flametube as previously, I'd need to increase the diameters of both the front and rear walls of the NGV , and this would require changes to the evaporator position to a greater radius which then makes positions it less favorably in the flametube at the evap outlet ...............compromises and more compromises :-(

Cheers
John

[racket]

As the engine build is up to the stage where its time to think about getting oil in and out of the engine I felt I needed to do some flow testing of supply tubing sizes to determine the smallest size that I can use, ............ space is limited in the engine and the smaller the tubing the easier it will be to fit .

But not having an oil pump on my test stand ...........it was fitted to the GT6041 kart build jetandturbineowners.proboards.com/thread/78/garrett-gt6041-powered-kart?page=4 , it was time to construct another pump .

As I like the Subaru oil pumps with their inbuilt relief valves and oil filter housing I decided to use the same pump again but this time I'd construct it with a chain drive in case I wanted to drive a second pump, possibly a scavenge pump , from the one 24V 500W electric motor, which I'll be running on 12 volts to reduce rpm and flow from the pump to ~10 litres/minute .

A couple of "progress pics" whilst trying to get an idea of "where and how" to position things






The final design is somewhat more complicated than previous pump builds as this one requires a couple of ball bearings to support the drive shaft that couples to the pump tang .

Cheers
John

[smithy1]

Hmmmm....why does this look very familiar to me..?? LOL.. ;-)

John, do you have a source for the electric motor kind sir..??

Cheers,
Smithy.

[racket]

Hi Smithy

Yeh , same motor just this one is a 24 V motor and I think yours is a 36V one, could be wrong there , its been a while :-)

I use to get my motors from secure.oatleyelectronics.com//index.php?cPath=53 but it looks like they only have a limited range these days , my current motor has been sitting around for at least 4 years, there doesn't seem to be many suppliers here in Oz .

These guys have a huge range www.electricscooterparts.com/motors.html

The manufacturer www.unitemotor.com/en/productmin.htm , you might need to enquire about a local supplier .

Cheers
John

[enginewhisperer]

These guys have all the scooter motors

www.motiondynamics.com.au/

[racket]

Thanks Andrew

I've saved the Link to my Favorites :-)

Cheers
John

[racket]

Hi Guys

Oil pump finally together , just need to mount on test stand and hook up a 3/4" copper pipe suction line to the oiltank and some 1/2" copper pipe pressure line to do some flow testing .









Cheers
John

[smithy1]

That's "oil pump porn" John...excellent work indeed. Love the chain-sprocket setup..

Like the "Suzuki" headed bolt too..!

Cheers,
Smithy