"Fat Boy" 12/118 thrust engine

[racket]

Hi Guys

Bit of an update

The starter solenoid has been replaced by a 24V 500 Amp unit , the old solenoid pulled apart and it didn't look good inside :-(

Whilst waiting for other bits to arrive I've been doing some work on the gearbox .

The piston ring holder for the input shaft has been made and fitted with a TV94 turb end piston ring


It fits into the stainless steel mounting for the freepower shroud/ducting, which is mounted over the original alloy cap that holds the input shaft bearings in place, there'll be a "thermal" gasket in between .

Then it was time to machine up the adapter that slips over the original input shaft and onto which the freepower wheel is installed , getting the "round" bits done was a bit fiddly with my old lathe but eventual it was done , which left the shitty job of machining the 8 mm keyway into the blind hole bore



Once the keyway was done , not the best job , but it'll do , the adapter was sliced off and the various surfaces "massaged" into some semblance of precision with use of plenty of emery cloth to lap out the bore .



With the adapter a nice sliding fit on the shaft , the freepower wheel was mounted onto its position for a rough mockup



I've still to machine some recesses for the curvic teeth to mate up with , the adapter is in the mill rotary table and ready for tomorrow .

Cheers
John

[Chuks]

Hi John,
Nice Job... I will just relax and copy your method when I get to the free stage build.

[racket]

Hi Chuks

LOL.......you're welcome to use it :-)

I had to bore out the coupling part of the turb wheel after mounting it onto a firm push fit mandril in the lathe , its tough material , very slow rpm and plenty of cooling fluid for small cuts

Cheers
John

[racket]

Hi Guys

The adapter's curvic recesses machined using a 5 mm endmill , the recesses are ~2 mm deep , theres 20 curvics on the wheel but I only machine 19 recesses as I remove one of the wheel's curvics to provide positive indexing of the wheel to adapter/shaft for balance maintenance.





With the adapter in place its possible to rotate the wheel a few degrees either way without the curvic touching the adapter , this verifies that the wheel is actually mounting against the middle shoulder on the adapter.

Just a thick washer required under the 6 mm securing screw to secure the wheel to the shaft, I'll try and incorporate a thin flange that can be bent into the curvic recess on the wheel for locking purposes

Cheers
John

[racket]

Hi Guys

The last couple of days have been taken up with getting the main mounting tube turned up and heat shrunk onto the mounting flange , used 4" Schedule 40 stainless 304 pipe for the mounting tube .

A slow job giving it a rough squaring up and machining to length , then around half the bore length needed machining out to ~109 mm for the mounting flange to have a squared shoulder to sit against.

After cooking the mounting tube in the kitchen oven for 30 minutes at 250 C, and freezing the flange in the fridge's freezer compartment , it was time to drop the flange into position and hold firmly for a few minutes until the two pieces became one , I'll run several small TIG welds around the joint just to be on the safe side .

A few pics


Theres a few millimetres clearance between tube ID and alloy casing for some ceramic blanket



Just enough space for the 6 X 6mm socket head screws that will hold everything to the gearbox



Turb wheel roughly in place , the gap between wheel and tube will be less once a gasket is under the mounting flange , possibly some bleed air fed into the tube to keep shaft bits and back of wheel cool



Cheers
John

[Deleted]

Hi John

Coming together nicely, that gear box is a very nice compact unit

Chat Soon
Andy

[azwood]

So is this going in a kart? If so i cant wait to see that.

[azwood]

youtu.be/Jm79PKoWY7M have you seen this kart not sure its real a vid of it actually driven would be good

[racket]

Hi Andy

Yep , nice and compact , unfortunately the "hot" parts are going to be a bit bulkier if we're going to get a few pounds of hot gases through it every second ;-)

Cheers
John

[racket]

That steam turbine is an interesting creature , don't know about that claimed horsepower though , it appears to be using some sort of airstart unit for the gearbox

[azwood]

Jul 8, 2018 4:31:52 GMT -5 racket said:

That steam turbine is an interesting creature , don't know about that claimed horsepower though , it appears to be using some sort of airstart unit for the gearbox

I thought it was a carbin monoxide rocket seen a few in karts

[azwood]

Jul 8, 2018 4:13:26 GMT -5 racket said:

Hi Andy

Yep , nice and compact , unfortunately the "hot" parts are going to be a bit bulkier if we're going to get a few pounds of hot gases through it every second ;-)

Cheers
John

Should be impressive to drive what power do you expect from it.

[racket]

Probably 200+ HP .

That steam turbine uses hydrogen peroxide decomposition to produce steam which is then fed to the turbine , but its 1,500 HP claim might be a tad exaggerated , it looks like the turb wheel was oversped and threw chunks off , possibly a transmission failure allowed the overspeed as the trans doesn't look up to the job for that sorta HP .

[azwood]

Yeah i call bs on the hoursepower they say

Jul 8, 2018 19:11:28 GMT -5 racket said:

Probably 200+ HP .

That steam turbine uses hydrogen peroxide decomposition to produce steam which is then fed to the turbine , but its 1,500 HP claim might be a tad exaggerated , it looks like the turb wheel was oversped and threw chunks off , possibly a transmission failure allowed the overspeed as the trans doesn't look up to the job for that sorta HP .

[racket]

Hi Guys

I've been doing a bit of thinking on my "jetpipes" and the possibilities that my original one is giving me problems even though the new "big" jetpipe won't allow me to even get a successful spoolup .

To test the "theory" I've added an extra sleeve into the new pipe so that the exducer shroud section is the same as the old pipe , which should allow me to get a spoolup with it fitted,

A coupla pics





The new pipe had been made with ~5 mm radial clearance over the exducer to increase flow area , this undoubtedly reduced the wheels power producing capability below what was required for a spoolup , reduced power was expected , but I'd hoped the starter would have got me "over the hump".

Now heres my reasoning for the old pipe giving me grief .

I've been looking at some of those colourful CFD pics of NGV flows and noticed a considerable low velocity wake downstream of the vanes .

My 111mm dia exducer vanes have been clipped considerably resulting in a fairly large flat end , ideal for producing a wake , also the hub has a nice big fat flat 36 mm dia end , again a potential wake producer.

Because of the clipping and the way I've got the turb stage configured for high flow through speeds , the "axial" exit velocity from the wheel is much greater than normal , again a contributor to increased wake producing potential .

The theoretical jet nozzle sizing for the engine is a 4" one , so I felt a 104 mm nozzle would be ample , the old jetpipe has a ~108 mm exit , plenty big enough I felt not to cause problems .

BUT ...........I love buts , if I subtract the downstream area of the wheel's exducer blades and hub , assuming they are producing a low velocity wake , then the 108 mm opening of the pipe is severely undersized , with an "effective" area equivalent to an 89 mm nozzle.

With the new pipe installed , hopefully theres no "restriction" downstream , the several mms of radial increase in diameter immediately downstream of the exducer should provide space for the flows to smooth out .................I guess I'll know as soon as it fires up , if the temps are lower its a success , if not , then back to the drawing board .

Cheers
John