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Post by smithy1 on Aug 17, 2014 22:30:02 GMT -5
Hi Guys, I'm returning after a bit of a Hiatus..  As some of you may know....I'm the lucky one who was blessed with John's GT6041 powered afterburning go kart, I did about 0.01% of the work on it, John did the other 99.99%  Thanks a bunch John..! You're a wonderful asset to this forum and to people who play with turbines in general. I've had the "Green Beast" sitting in my shed for quite some time and whilst I've always had it in my thoughts, I never did anything about getting it back up and running, my missus was giving me some grief just the other week saying "you'll never get it going"....well...I finally bit the bullet and ran it a couple of weekends ago. All I did was check all the fuel lines and connections for signs of deterioration etc...all I found was a few fuel lines a bit perished and the battery needed top-up charging, so I replaced the fuel lines, charged the battery and took the kart to my friend's place, with a nervous twitch in my eye I attached all the necessary gubbins to make it run, topped up the fuel, connected the propane start line, hit it with the blower, held my tongue in the right place  and she just fired up straight away, I only ran the single tank ~8-9 liters of fuel through it....I don't know what all the fuss was about  . Idle is set at ~4.5-5psi P2 and I'm seeing ~460c egt..... I suspect it'll run, (self sustain), at a slightly lower P2 but John and I have discussed it a few times and it's a nice round number! I've restricted the max P2 to 35psi for the moment until I get my head around all the nuances of the setup, then I might push her a tad harder, the comp map says she can handle quite a bit more so I've got plenty of squirming room to play with in case of an A/B flame-out resulting in a bit of an overspeed. I'm planning to do a bit of car/hot-rod show work with this beast, I'm going to replace the tyres during the next week or two as the originals are a bit perished and may be unsafe, it will be my first attempt at a car show with the go kart, (just a static exhibition), this next coming weekend, Sunday 24th, I'll also have my little 1/4 scale turbine powered dragster there....it's just a small local car show but I'll be quite nervous just the same.!! Cheers and wish me luck, Smithy. |
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Post by enginewhisperer on Aug 18, 2014 0:47:47 GMT -5
good luck! keep us posted - I'll try to come and have a look / lend a hand when you run it |
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Post by racket on Aug 18, 2014 4:13:52 GMT -5
Hi Smithy
LOL........you'll have fun at the show letting kids sit in the seat and "dream" about driving her, whilst their old man takes some pics for their Facebook page :-)
I'll be looking forward to hearing about some extended afterburning tests, mine we're far to short at the time in deference to my long suffering neighbour's.
Cheers
John
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Post by smithy1 on Aug 18, 2014 15:29:00 GMT -5
good luck! keep us posted - I'll try to come and have a look / lend a hand when you run it Really..?? That'd be cool...whereabouts are you? |
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Post by smithy1 on Aug 18, 2014 16:06:19 GMT -5
Hi Smithy LOL........you'll have fun at the show letting kids sit in the seat and "dream" about driving her, whilst their old man takes some pics for their Facebook page :-) I'll be looking forward to hearing about some extended afterburning tests, mine we're far to short at the time in deference to my long suffering neighbour's. Cheers John Hi John, Great to be back and talking with you all.....I did play with the A/B whilst at Cameron's place a couple of weekends ago, I was only able to get the occasional pop and fart out of the A/B during a solid acceleration, methinks a small amount of combustion flame during accel was enabling the occasional pop/fart. Apart from that the engine is as sweet as a nut, oil pressure is excellent @ ~50-55psi when warm, egt's are spot on ~460c @ 5psi P2 and ~630c @ 35psi P2 which leaves plenty of temp margin wiggle room, throttle response is superb and not even a hint of surge during full throttle hits... I'm impressed with your combustion chamber and fueling work....well done Sir..! As mentioned earlier, I have limited the P2 to ~35psi until I do some more engine and A/B test running. I'm hoping to get an rpm sensor fitted in the near future, I'm just curious as to self sustain rpms for reference etc...I'm going to try and cannibalize one of those cheap reflective rpm sensors and fit the "eyeball" to the inlet housing and see about extending the wiring so I can have the readout somewhere on the dash..! I'll use either the reflective tape or just polish one flat of the comp nut and paint the rest black and see what happens, ....should hopefully work either way. I have "rewired" the P2 pressure safety-A/B enable switch so I can run the A/B at any rpm/P2 pressure, good for big fluffy flame shows  ....I suspect the Jacob's ladder just doesn't have enough grunt to light her up so I have now made and fitted a full stainless "hot streak" system with a 1.0mm nozzle poking through one of the large tertiary CC holes and lined it up with the turbine inlet. I have it running through a nice big robust solenoid via a second switch on the steering wheel....which means I can have the nice big white smoke and also light her up via the momentary hot-streak.....  Hopefully the weather will be kind to us this coming weekend so I can at least get a couple of engine runs in whilst at the car show. As mentioned earlier, I have new wheels and tyres coming this week, the only issue I might have is the original rear wheels are actually 6" diameter "super-kart" wheels, not the normal 5" diameter wheels fitted to most karts....this may mean I loose ~1/2" of ground clearance at the rear....hopefully it'll be ok..! I'm also thinking of fitting a "fourth" rear axle bearing and retainer sleeve via another bearing support next to the original center bearing support, I can then cut the axle between them which should enable the kart to actually turn.....as you're well aware, a solid rear axle tends to make the poor thing understeer terribly unless you're lifting a wheel through the corner like a normal go kart would. Should make it easier to maneuver the beast around at car shows and even in my shed too..! Cheers, Smithy. |
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Post by racket on Aug 18, 2014 17:45:48 GMT -5
Hi Smithy
You'll probably need ~25,000 rpm for self sustain and maybe a bit over 30,000 for an idle.............when I was testing the 10/98 engine with a same diametered 141mm comp I needed ~35,000 rpm for a decent idle , one of the unknowns is where on the map we are flowing , at the bottom of the map if we flow a bit to the high flow choke side the rpm line curves over pretty quickly for the pressure developed.
Good idea to get the hot streak fitted, you've a well sorted setup on the 1/4 scale engine, no point reinventing the wheel :-)
The 6" dia afterburner is right on the lower limit for diameter , I'd have preferred a more accommodating 7" inch one but that size didn't come "off the shelf" , the 8" would be a bit large with extra losses ...............I found I needed to light the A/B at fairly low P2 pressures/flows where the gas velocities at the flameholder were more conducive to ignition .................one other point was the fuel flow rate from the single A/B fuel pump wasn't enough to give a rich mixture at full mass flow , she'd be running rather lean and perhaps outside ignition range, the lower air flow at lower P2 pressures would have produced a richer mixture , maybe a combination of a couple of things , I'm certain you'll have no problems getting the A/B sorted and running as sweet as the 1/4 scaler .
Because we run a fixed A/B nozzle area prior to igniting the A/B , the "dry" mass flow rate could be well into the high flow side of the map as theres less downstream restriction making it necessary to ignite the A/B at lower P2s and "lower" flows which might not be a lot lower than at high P2s with the A/B alight and putting the design back pressure on the engine and keeping compressor flows under control .
Heh heh .....lotsa things for you to play with :-)
Cheers
John
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Post by enginewhisperer on Aug 18, 2014 18:05:12 GMT -5
good luck! keep us posted - I'll try to come and have a look / lend a hand when you run it Really..?? That'd be cool...whereabouts are you? I'm in Sydney. I seem to recall you are too? It'd be good to get some extra motivation to get my 6041 turbine up and running just a couple of other projects to get out of the way first.... |
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Post by pitciblackscotland on Aug 18, 2014 18:39:06 GMT -5
Hi Brett,
Good to see you back on here mate. Are you still going to test the Mamba Monster motor to start the engine??
CHeers,
Mark..
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Post by smithy1 on Aug 18, 2014 20:03:04 GMT -5
Really..?? That'd be cool...whereabouts are you? I'm in Sydney. I seem to recall you are too? It'd be good to get some extra motivation to get my 6041 turbine up and running just a couple of other projects to get out of the way first.... Excellent....I live at Campbelltown. I'll be at a car show at Minchinbury on Sunday if you'd like to pop out for a looksee, weather permitting of course, (you can get me at smith.brett2@gmail.com). I could definitely use the help too. Not entirely sure if I'll have the kart running on Sunday but will definitely have the 1/4 scale jet dragster running. I usually get my 21yo son to give me a hand to run the kart but he can't always come out to play. He usually holds the blower on the inlet while I fiddle with the rest of the gubbins during start. On a side note...my new Dunlop SL1A go kart slicks just arrived ~ten mins ago  Bonus....just need the new wheels to turn up in the next day or so and I'll be good to go..! Cheers, Smithy. |
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Post by smithy1 on Aug 18, 2014 20:32:34 GMT -5
Hi Smithy You'll probably need ~25,000 rpm for self sustain and maybe a bit over 30,000 for an idle.............when I was testing the 10/98 engine with a same diametered 141mm comp I needed ~35,000 rpm for a decent idle , one of the unknowns is where on the map we are flowing , at the bottom of the map if we flow a bit to the high flow choke side the rpm line curves over pretty quickly for the pressure developed. Good idea to get the hot streak fitted, you've a well sorted setup on the 1/4 scale engine, no point reinventing the wheel :-) The 6" dia afterburner is right on the lower limit for diameter , I'd have preferred a more accommodating 7" inch one but that size didn't come "off the shelf" , the 8" would be a bit large with extra losses ...............I found I needed to light the A/B at fairly low P2 pressures/flows where the gas velocities at the flameholder were more conducive to ignition .................one other point was the fuel flow rate from the single A/B fuel pump wasn't enough to give a rich mixture at full mass flow , she'd be running rather lean and perhaps outside ignition range, the lower air flow at lower P2 pressures would have produced a richer mixture , maybe a combination of a couple of things , I'm certain you'll have no problems getting the A/B sorted and running as sweet as the 1/4 scaler . Because we run a fixed A/B nozzle area prior to igniting the A/B , the "dry" mass flow rate could be well into the high flow side of the map as theres less downstream restriction making it necessary to ignite the A/B at lower P2s and "lower" flows which might not be a lot lower than at high P2s with the A/B alight and putting the design back pressure on the engine and keeping compressor flows under control . Heh heh .....lotsa things for you to play with :-) Cheers John Hmmm....25k for self sustain seems a tad high, my little 1/4 scale engine will happily spin along at ~19-20k, I have the starter coming off @ 18k and it will happily run up to the 33k idle I have set without drama, I have the top end set to 125k so there's a nice big rpm range with that engine. The hot streak is really a no brainer, it's the only effectively 100% reliable way to do it, just a matter of sorting nozzle sizes and flow rates.... and aiming it in the right direction. You're right about the A/B pipe diameter, could do with another inch...(I guess we could all do with an extra inch , it is winter here after all), to try and keep velocities under control..... as long as I light it up at a reasonably low rpm/P2 it "should" stay lit...I have the same issue with my little dragster...she won't light up after ~70-75%.....eflux speed is getting a bit high or close to the limit I suspect....too much wind in there..! Still get some nice burner "pops" at 50-60% though.. Regarding the lean A/B fuel flows at higher P2 pressures, I'm contemplating fitting a higher capacity pump, (pressure and flow rate). At this stage the original item will suffice for now. One thing at a time..! Cheers, Smithy. |
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Post by smithy1 on Aug 18, 2014 20:51:13 GMT -5
Hi Brett, Good to see you back on here mate. Are you still going to test the Mamba Monster motor to start the engine?? CHeers, Mark.. Hey Mark, I did actually get the Castle 1717 motor fitted and running on the GT6041, I had difficulties getting the starter bendix to disengage when up to self sustain speed though, the 1717 motor is good for 45k and it had plenty of grunt to play with.....just got a bit complicated to set up etc....the petrol powered blower John supplied with the kart works fine and is pretty idiot proof, I'm proof of that ....I may look into the electric start side of things again soon, but it's not a necessity, just a luxury. I do like the idea of just flicking a switch and turning a propane valve to light the engine off though. Cheers, Smithy. |
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Post by racket on Aug 18, 2014 21:11:28 GMT -5
Hi Smithy
Yeh , those RC engines have very low idle rpm percentages , gotta have them to reduce idle thrust to an absolute minimum for landing at reasonable speeds , but then they can have longer ramp up times to get to max throttle and rpm settings , we can idle a bit higher and not worry about banging the throttle wide open, most of the auto gas turbines had idle rpms at >50% N1,..... even at 30,000 we're at less than 50% , I did notice the 9/94 and FM-1 engines we're able to idle a bit lower due to the ball bearings, but with the brass bushes and cold thick oil we need more fuel during a spoolup to get to a "safe" idle , once warmed up with thinned out lube its possible to drop idling back to 3-3.5 psi P2 , possibly even lower if we didn't mind some rotor acceleration "lag" time .
The bottom line on the GT60 comp map is at ~29,000 rpm for a PR of ~1.3 or ~5psi P2 which is at ~40% N1 , doesn't the good old Allison C20 ground idles at ~65% N1.
You could say the RC engines idling at ~25% are a bit of an odd man out when it comes to idling percentages, the fact that their rotors are so light, both actual and relative to mass flow , means they can get away with those low idle rpm and still be able to accelerate the rotor within a reasonable time frame .
Yep , more fuel for the A/B :-)
Cheers
John
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Post by Richard OConnell on Aug 18, 2014 21:18:34 GMT -5
Hi Smithy, welcome back! Did ya lose the keys to your other account? |
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Post by smithy1 on Aug 18, 2014 22:41:51 GMT -5
Hi Smithy, welcome back! Did ya lose the keys to your other account? Hey Richard, Thanks for the kind welcome back..! Yeah, has been so long I've forgotten my old passwords and log-ins etc....not to worry...all good now. Must be close to two years or so I suspect. Cheers, Smithy. |
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Post by smithy1 on Aug 19, 2014 16:15:08 GMT -5
Morning Gents, John...The nice new magnesium wheels for the "Green Beast" arrived late yesterday , these ones: www.cutpriceracing.com.au/store/Complete-Magnesium-Rims-Set-Bolt-On-Type-Fronts-Brand-New/Along with the new Dunlop SL1A slicks she should be "just like a new one"..I checked the ground clearance and I should be ok, the fronts are the same as the old but the original rear tyres are 12"x8"x6", the new ones are 11"x7.1"x5"....I'm only loosing 1" in overall diameter so 1/2" of radius, with ~40psi in the tyres I should be good to go. Max pressure is 4.0 bar (~58psi) so plenty to play with. I've also ordered a Bosch 044 fuel pump to sit alongside the original A/B pump, I believe they're good for ~4.5-5 bar @ 285l/h...so that should cure the "lean A/B" issue..! I've ordered up a "twin" pump clamp assembly to make it all look nice...this one: www.ebay.com.au/itm/271577932513?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649 I plan to have an adjustable fuel flow valve in the line downstream of the pumps so I can actually vary the fuel flow/pressure to the A/B to give the best performance....or to give the best flame show.....whichever is applicable on the day..! Hopefully I can get the wheels & tyres fitted up in the next day or so and I'll take a photo for the lads and post it here..! I'm actually getting quite excited about getting the beast up and running as it should....and for it to be drivable and as safe as possible.... Cheers, Smithy. |
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Thanks a bunch John..! You're a wonderful asset to this forum and to people who play with turbines in general.
and she just fired up straight away, I only ran the single tank ~8-9 liters of fuel through it....I don't know what all the fuss was about 
. Idle is set at ~4.5-5psi P2 and I'm seeing ~460c egt..... I suspect it'll run, (self sustain), at a slightly lower P2 but John and I have discussed it a few times and it's a nice round number! I've restricted the max P2 to 35psi for the moment until I get my head around all the nuances of the setup, then I might push her a tad harder, the comp map says she can handle quite a bit more so I've got plenty of squirming room to play with in case of an A/B flame-out resulting in a bit of an overspeed.
....I suspect the Jacob's ladder just doesn't have enough grunt to light her up so I have now made and fitted a full stainless "hot streak" system with a 1.0mm nozzle poking through one of the large tertiary CC holes and lined it up with the turbine inlet. I have it running through a nice big robust solenoid via a second switch on the steering wheel....which means I can have the nice big white smoke and also light her up via the momentary hot-streak..... 
Hopefully the weather will be kind to us this coming weekend so I can at least get a couple of engine runs in whilst at the car show.
Bonus....just need the new wheels to turn up in the next day or so and I'll be good to go..!
