2 shaft turbine kart build

[Richard OConnell]

Me, Ernie, and Chris talked about building a kart. Chris made one a while back, but we were thinking of experimenting some with using free turbines rather than thrust. Chris has some experience since his van's rear axle is driven by a nimbus helicopter engine that produces ~800 shaft horsepower if I'm not mistaken... I think the weight would be a bit excessive for a go kart, but I might be looking into other free turbines that were designed for smaller applications.
Chris's Kart: www.youtube.com/user/krugtech#p/u/20/6Waf2ycyKWY
Chris's Van: www.youtube.com/user/krugtech#p/u/19/wQM_TyyRye4

[racket]

Hi Richard

Chris' kart was a great inspiration for me when I was still developing my turbine bike , over several years I'd gotten it up to maximum thrust potential as a pure jet , but was having a lot of trouble sourcing a freepower turbine wheel , so ended up fitting a rather long jetpipe and nozzle on the side of the bike with the intention of running under her ~110 lbs of thrust , the only "road test" was around the backyard , it did move under its own power , but rather disappointingly .

Before I had a chance to give her a decent test on a piece of straight road I was able to source a freepower wheel from an Alco turbo off a locomotive, it was a little large at ~10" dia , but it was better than nothing so started designing up for it , in the mean time my mate Andrew sourced a third stage wheel from a C20 engine and I eventually used it for the bikes freepower , it worked OK :-)
www.youtube.com/watch?v=q_MRUxWEOZ0
www.youtube.com/watch?v=P-5PgWqgIJo
www.youtube.com/watch?v=CplnY9TG7NE with 115 rear wheel hp.

I was in contact with Chris when he was constructing the van and we had some discussions about the power transmition drive line , chains and sprockets vs gears , having had a lot of experience with bikes over 40 years I felt the sprockets would be OK , not sure what he ended up using , but whatever it was .......that van mooooves :-)

Theres not a lot of freeturbine equiped small engines out there , unfortunately most small APU sized turbines are single shaft engines , maybe a small Boeing 502 would do the job ,
www.youtube.com/watch?v=Ezrf9veTMkk
and theres always the JFS units as in www.youtube.com/watch?v=sWUxI08C4dk

I'd certainly like to see some more turbine karts out there , theres really no comparison between a shaft powered kart and a thrust one , ideally we need a centrifical clutch on the output shaft to get some instant horsepower from a rotating freepower wheel

All food for thought, I hope something eventuates for you guys :-)

Cheers
John

[Richard OConnell]

I might be mistaken, but the Boeing 502 looks a little big for a turbine kart, unless you are looking for a long-body build. I think something smaller like an APU would be more appealing.
Theres a pretty neat looking Lycoming T-53 on EBay that looks comparable in size to the 502 and If you were looking to make a longbody shaft driven dragster it would be perfect. The price is a bit steep though right now.

[Richard OConnell]

Lycoming T53-L-13B Turboshaft Engine


Type: Dual spool, free shaft turbine
Inlet: Axial, with variable geometry inlet guide vanes
Compressor: Mixed flow; 5 stage axial, 1 stage centrifugal
Burner: Reverse flow annular with 22 fuel nozzles
Turbine: Dual spool, two stage axial gas producer turbine, two stage power turbine
Exhaust: Rearward facing, single exit axial flow diffuser
Power Rating: 1,400 shaft horsepower @ 6,640 rpm
Rated Torque Output at full power: 1,200 lb/ft @ 6,640 rpm
Peak Torque Output: 1,700 lb/ft @ 1,800 rpm
Weight: 540 lbs.
Power/weight: 2.6 lb/shp
Compression Ratio: 7.2:1 at 25,600 rpm
Specific Fuel Consumption: .58 lb/shp/hr

[racket]

Hi Richard

Mmmm, interesting numbers on the T53 , especially that max torque limitation , the gearbox could be a bit fragile if it can only handle 1,700 ft/lbs at 1,800 rpm , normally a freepower produces twice peak rpm torque at nil rpm or ~2,400 ft lbs in this case , aero engine can have torque limitations due to the fact they"can't" stall their freepower wheels , as soon as the gas producer starts turning at any sort of decent rpm the freepower starts to slowly turn effectively lowering its potential max torque , therefore no need for a "stronger" gearbox . .................I've been told the Allison C20 engines have torque limitations on their redux units .

LOL....the T53 is a bit too large for me , I like to be able to lift my engines , ready made engines are beautiful bits of engineering that I love to inspect/steal ideas from , but I like to make my own , heh heh ...I get more of a kick out of the creation than the use of them , after a few uses I get bored with the vehicle they're in , whereas the building can be spread over several months of creativity..................you could say I'm more of a metal working "artist" than a driver/rider of turbine powered vehicles ..........................been the same since I was a kid , I'd be the one making/repairing the machines whilst other kids used/abused them , 50 years later I'm still doing it ............sometimes nothin' changes in life :-)

Cheers
John

[racket]

Then it was time for getting a 12 volt lube pump sorted .

Biggest problem was finding a powerful enough 12 volt motor , I eventually used one from a large air compressor of ~1/4 hp .

Actual lube pump was a little more complicated , I needed one with filter attached and internal relief valves etc , Subaru automotive pumps were ideal as they were externally mounted and lightweight alloy construction , just needing a mounting pad machined up and some method of transmitting power between 12 volt motor and pump.

Sprockets and chain were decided up so that easy ratio changes could be made to "tune" the pumps output to the turbo's requirement .

Initially started with a 43 tooth on the oil pump , 4.3 :1 ratio , but flow was restricted to ~5 litres/minute at 40 psi with 10W-30 oil .

The Garrett TV84 turbo , being the largest in the "4 inch range" suffers from a fragile thrust bearing at high pressure ratios ( lotsa boost) , something I found out through bitter experience with my jet bike's development using this turbo , after replacing a few thrust bearings I eventually took the necessary step of running lube pressures of ~90-100psi , so this Subaru pump needed its pressure relief valve spring upgrading to something a bit stronger , that would produce the desired ~90 psi lube pressure .

During latter motor run testing it was found that pump flow was insufficient and a 35 tooth sprocket was fitted (3.5 :1 ratio) , this also proved inadequate and eventually a 25 tooth sprocket was used (2.5:1 ratio) along with heavier 15W-50 semi synthetic oil to maintain pressure at higher running temperatures .

Some 6 years latter I'm still using Subaru oilpumps (EA71 model) for my experiments , but now directly mounted to 500W 36 Volt motors being run on 12 Volts at ~900 rpm .

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[racket]

With a reasonable lube system fitted to the kart I could turn my attention to the flametube and combustion systems.

Evaporative fueling was decided up to simplify fuel pump requirements , a relatively "low pressure" (100psi) out of tank- inline Bosch EFI pump was sourced from the auto wreckers , upon testing it was found to produce >2 litres/min of flow , plenty of fuel .

Because the TV84 turbine wheel has tip height of 17mm it was decided that 19mm-3/4" diameter evaporators would be used in case anything came loose it couldn't enter the turbine scroll "slot" and wheel .

Tubing used for the evaporators was 19mm diameter by 1.2mm wall thickness 304 stainless , the "legs" of the evaporators were 95mm for the first leg then 50mm for the radial leg then 55mm for the return leg , mitre joints naturally reduced inner lengths .

A jig was used to hold the various pieces in position for tack welding before removal from the jig and final TIG welding of joints

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With each of the 4 evaporators welded together , it was time to workout how they needed fitting into the ~140mm dia flametube cap and how to mount/orientate/construct the fuel injection .

It was decided that fitting the 4 evaporators " back to back" in a cross configuration would provide the best coverage of the flametube crossectional area and allow a single fuel injector tube to be used

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Prior to welding the evaporators into the endcap , each evaporator required machining at its inlet end to provide "indexing" for the injector tube and a clearance slot for the fuel spray

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The indexing of the injector was achieved by means of a screw in square headed bolt at the end of the injector tube , with fuel being delivered via 4 X 0.7mm diameter holes axially displaced above each of the bolts 4 flats .

The fuel injection holes were drilled with some axial angle so as to squirt the fuel across and down the evaporator opening to prevent any "sprayback" .

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[racket]

The injector tube was a length of 3/8" OD heavy walled alloy tubing , it allowed the injector to be fitted in any of the 4 possible positions dictated by the square indexing head at its end , the fuel delivery holes all being in the same position relative to a "flat" allowed the injector tube to be fitted anywhere , just a matter of pushing the tube home as far as possible and tightening the "nut and olive" that secured and sealed it in position within the hollow flametube securing tube at the end of the flametube .

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[racket]

Once the evaporators were welded into position it was possible to fit the flametube securing tube and "top" of the displacement/stand off ring that held the flametube away from the outer can end whilst allowing air into the evaporators .

The flametube securing tube was fitted thru the outer can end cap and was secured in place with a locknut on the threaded portion of the tube , the fuel injector securing/sealing fittings were screwed onto the end of the flametube securing tube .

Preheat propane was fed coaxially down the securing tube, around the fuel injection tube , and into the "standoff" chamber and mixed with evaporator air before passing thru the evaporators and into the flametube where it was ignited by a suitably positioned spark plug where it then heated the evaporators prior to the kero being injected during spoolup .

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[racket]

With the evaporators and endcap made it was time to construct the rest of the flametube .

The 4 evaporator outlets needed air to be blown across them along with intermediate turbulance holes provided in the primary zone .

Rows of small cooling air holes to keep the sheet of 0.5mm thick 304 stainless insulated from the hot gases were provided along with secondary and tertiary holes for dilution .

Total area of all holes including the evaporators was a little greater than the comps 3.5" inducer area , ~30% for primary , 20% secondary and 50% tertiary

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Closeup of the flametube wall holes surrounding the evaporators , the 2 X 6mm dia holes close together at the very top of the FT wall forced air to mix with the vapourised fuel/air mix exiting the evaporators as well as providing turbulance .

The two lower 6mm dia holes were between the evaporator legs and had their hole shape bent, using a tapered steel rod( centre punch) , so as to produce a stream of air flowing back towards the FT cap rather than a purely radial entry , this manipulation of the hole orientation helped produce more turbulance and hopefully some recirculation of flames/hot gases to improve combustion times ,

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Connecting the combustor to the turbo comp housing .

A diffusing cone was silver soldered onto the outer can wall over the entry holes thru the outer can wall , a web of outer can wall was left in place to strengthen the arrangement

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