"Fat Boy" 12/118 thrust engine

[racket]

Hi Guys

A bit more progress






Time to cut some "legs" for the "spider", 7 required to prevent "phasing" as theres 36 wheel blades, 3 X 30 mm stainless flat for the legs, hopefully they won't buckle due to their higher expansion rate than the steel at each end , I'm counting on the bleed cooling to the root mount to even things out .

Cheers
John

[turboron]

John, tangential struts are a better solution. The radial struts usually start cracking after a few hours of service.

Thanks, Ron

[racket]

Hi Ron

Good suggestion :-)

I'll see if I can work something , I've used tangential struts in my jetpipes at times to support a central tube .

LOL.............a few hours might be many times what this will see ;-)

Cheers
John

[racket]

Hi Ron

I had to go with radials , the tangentials would have perhaps created torsional stresses in the scroll housing , I can live with a few hours life :-)

A bit of video youtu.be/DLEEj7wUnUU , amazingly the wheel span without binding, LOL....musta got things right .

And a few pics









Horrible job turning down the "spider legs" to fit the shroud , slow rpm and things caught with the chuck being unable to hold the thin tube , fast and the tool burnt out requiring innumerable sharpenings even though only taking a few thou at a time , but eventually got it done .

I normally leave a small "step" at the inner end of the legs, only a half millimeter, but it allows for easy alignment of shroud and legs in all planes , the small projections are handy to weld over.

Cheers
John

[turboron]

John, I am surprised to see the struts set with such an angle to the flow. Are you expecting a lot of residual swirl off of the wheel. Most radial struts are axial with the centerline of the engine since the turbine designer shoots for no swirl at the turbine wheel exit.

Thanks, Ron

[racket]

Hi Ron

LOL.....the struts are on the inlet side of the wheel , they're "guide vanes" out of the scroll .................it'll become more clear as I make the tin work.

Cheers
John

[racket]

Hi Ron

This might explain things .

The gases will be fed into the side of an Achemedian Screw , and then "augered" into the wheel through those 7 struts which are set at the same "pitch angle?? of ~20 degrees, it worked on my TV84 bike and seems to work on the freepower stage I made for Andrews bike jetandturbineowners.proboards.com/thread/34/motorcycle-project ......... www.youtube.com/watch?v=mWt9Pf3oY8s

Currently trying to get "the screw" cardboard pattern right , minor changes to the ID and OD seem to have mixed results , I'm on my 4th one at present , similar to my first try, which I subsequently stuffed around with to "improve" it , only to make a complete mess of it ..............ah well , cardboard is easier to work with than metal , so I'll keep trying .







Cheers
John

[turboron]

John, Achemedian Screw is an interesting approach. It seem simpler than the common industrial practice of "pair of pants" (one leg on each side of the shaft) stainless steel fabrication with laser cut cooling holes. The "pants" are difficult to manufacture with a lot of cracking during fab and use. Have you seen the screw used elsewhere or is it your idea. Patent?

Thanks, Ron

[racket]

Hi Ron

I sorta pinched the idea after checking out a WW2 aircraft turbo supercharger, like this... www.google.com.au/search?q=B-31+aircraft+turbo+supercharger&hl=en&tbm=isch&source=lnms&sa=X&ved=0ahUKEwib5O-JrZfkAhXFPI8KHVwwA1EQ_AUICigB&biw=1904&bih=920&dpr=1#imgrc=h_TnHb_ugS5fKM: that Andrew had in his shed , it was nice and "compact" in the axial direction which is something I needed when trying to fit an axial freepower wheel into a bike scenario, where the orientation of parts wasn't the best .

Theres undoubtedly more losses than a conventional NGV , but it does produce a nice clean uncluttered exhaust from the wheel which should offset the inlet side losses to some degree especially if a diffusing exhaust is fitted.

On my TV84 bike I made the "scroll" more like a conventional type with reducing cross sectional size as it curled around the central tube , but on Andrews setup I went to the "screw" fitted inside a simpler shaped outer "container" that was easier to manufacture, the screw didn't need to be "sealed" as it was only a guide mounted inside the outer pressure vessel, the throat of the scroll was at the start of the screw , this created the design(LOL) gas speed which then continued on around the scroll as the gases were hopefully screwed through the wheel .

I guess my torque tests will soon show up any flaws in my design ............stay tuned :-)

Cheers
John

[turboron]

John, some of the WWII turbo stuff is very interesting. We had a pile of B17 turbochargers that we use to for test equipment. We removed the compressor and used the turbine part as a steam turbine. Very robust construction with integral blades and wheels.

Thanks, Ron

[racket]

Hi Ron

It seems those surplus turbos were used for quite a few uses besides their original one , there was even a turbojet conversion by GE of their B-31 turbo as an engine for their JB-1A missile in 1944 , but it was a failure due to the engines only producing half of the expected 400 lbs of thrust each was hoped to produce , their being two engines on the missile , it seems they changed both the NGV and wheel blades to a less "restrictive" pattern for the "jet" .

As a steam turbine they'd have been very handy as a high speed , high power driver for testing gas turbine "bits" .

Cheers
John

[racket]

Hi Guys

A few pics of the "metal bits" , I ended up using stainless as I already had the material and as this'll be my last build I thought I might as well use it up .







Cheers
John

[turboron]

John, how many degrees of circumference are open to the inlet?

Thanks, Ron

[racket]

Hi Ron

Mmmm...........now that might vary depening on how I'm able to manufacture the inlet ..........LOL, haven't thought too much about it yet ............its an "organic" construction , if it looks right , then I'll go with it .

Went and purchased the 114mm wide strip of stainless for the outer circumferential wall this morning , so will need to figure out how to blend a 5" diameter interstage duct into it and create the required "throat" area ............sheet metal work isn't one of my favourite jobs :-( .............but it'll eventually get done :-)

Cheers
John

[racket]

Hi Ron

Some more pics of the freepower scroll, slowly getting there , trying to align the slipjoint inlet was a bit of a hassle but its kinda "true??" and roughly where I want it , the 5" jetpipe from the gas producer simply slips in with several thou clearance.











Just gotta cut couple of side panels now and tack in place , then check everything before doing the final welds , weight ~7 kgs/15 lbs .

Cheers
John