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Post by racket on May 31, 2018 18:21:32 GMT -5
The fastest was ~70 MPH -120kph , this was over a measured distance using a stop watch for timing , the road I used was the access road to the local dam during its construction , generally used by big dump trucks , so not very flat , I was restricted by the roughness , the kart was bouncing all over the place at that speed , but still accelerating hard and wanting to go faster.
The freepower shaft ran a standard 10 tooth tapered bore kart sprocket back to an 81 tooth axial sprocket for an 8.1 :1 ratio , this gave an ~60 mph-100kph speed at ~15,000 rpm N2 , the karting chain I used was the best available and was supposedly good for 22,000 rpm at the "engine" which would have given ~90 mph-140 kph kart speed .
Cheers John
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Post by racket on May 31, 2018 19:28:49 GMT -5
And a bit more info from my Files .............I did a "drawbar" test back in May 2005 , and with a P2 of 15 psi I had 60 lbs of "pull", the large spring balance was connected to the kart chassis , at 25 psi P2 it was 80 lbs, 110 lbs at 30 psi , 130 lbs at 35 psi and 160 lbs at 40 psi P2.
Some video showed 0-50 metres took 5.1 seconds 50-100 metres 2.4 secs , 0-100 metres 7.5 seconds , a flying 100 metres in 3 seconds .
Initial acceleration was "slow" as with all single gear turbines ,they really need some sort of centrif clutch , but once the freepower is starting to get some rpm the power comes on quicker , there was a strong "push in the back" once past ~10,000 rpm
Cheers John
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Post by azwood on May 31, 2018 19:55:22 GMT -5
Ive watched your vid of the jetkart a few times its pretty awsome.i agree a cintrivical clutch would be nice and maybe some sort of flywheel to help get going And a bit more info from my Files .............I did a "drawbar" test back in May 2005 , and with a P2 of 15 psi I had 60 lbs of "pull", the large spring balance was connected to the kart chassis , at 25 psi P2 it was 80 lbs, 110 lbs at 30 psi , 130 lbs at 35 psi and 160 lbs at 40 psi P2. Some video showed 0-50 metres took 5.1 seconds 50-100 metres 2.4 secs , 0-100 metres 7.5 seconds , a flying 100 metres in 3 seconds . Initial acceleration was "slow" as with all single gear turbines ,they really need some sort of centrif clutch , but once the freepower is starting to get some rpm the power comes on quicker , there was a strong "push in the back" once past ~10,000 rpm Cheers John
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Post by racket on May 31, 2018 20:49:01 GMT -5
We need horsepower to accelerate , a stalled freepower turbine wheel produces torque , lots of it if the gas producer is at full throttle , but torque has to have a "distance in unit time" for there to be horsepower , once the turb wheel starts to rotate we get that "distance " , and the rpm start to give us both distance in time .
The stalled freepower produces roughly twice the torque that it does at max rpm , the torque line on a dyno map is roughly a straight line, thats why we only need a single gear .
I'll see if I can find a dyno map and post it .
Cheers John
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Post by racket on May 31, 2018 20:53:28 GMT -5
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Post by azwood on May 31, 2018 21:26:40 GMT -5
So if it had a cintrivical clutch it should get going better ? that would remove the stall at the start and then just move it to a higher rpm i guess We need horsepower to accelerate , a stalled freepower turbine wheel produces torque , lots of it if the gas producer is at full throttle , but torque has to have a "distance in unit time" for there to be horsepower , once the turb wheel starts to rotate we get that "distance " , and the rpm start to give us both distance in time . The stalled freepower produces roughly twice the torque that it does at max rpm , the torque line on a dyno map is roughly a straight line, thats why we only need a single gear . I'll see if I can find a dyno map and post it . Cheers John
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Post by azwood on May 31, 2018 21:27:38 GMT -5
Thats a steep torq curve nice
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Post by azwood on May 31, 2018 21:29:40 GMT -5
I see what you mean about 80 percent at half throttle
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Post by racket on May 31, 2018 22:40:05 GMT -5
Yep , we end up with a very "FAT" power curve . The guy doing the dyno didn't know that you could give the engine full throttle whilst it was sitting still ( stalled) hence the graphs only starting at his "normal" 75 kph. If he'd started from stall ( 0 kph) with the throttle wide open then the torque would have registered ~620 ft lbs , but with nil horsepower. This dyno run was done with part throttle at a P2 of ~25 psi , hence the lowish 93 horsepower figure at ~180 kph with only ~28,000 N2 rpm , with full power the horsepower should have maxed out at ~32,000 ( 100% N2) the torque figure at stall would be close to 1,000 ft lbs. The dyno was on Andrews bike build in Melbourne jetandturbineowners.proboards.com/thread/34/motorcycle-projectCheers John
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Post by azwood on May 31, 2018 23:40:09 GMT -5
Just got the kart i has loads of spairs including an engine so should recoup some cash back from them
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Post by azwood on Jun 1, 2018 1:47:09 GMT -5
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CH3NO2
Senior Member
Joined: March 2017
Posts: 455
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Post by CH3NO2 on Jun 1, 2018 12:42:46 GMT -5
Nice cart. Take it for a ride before you part it out.
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Post by azwood on Jun 1, 2018 17:22:30 GMT -5
Yep i will 😁 Nice cart. Take it for a ride before you part it out.
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Post by azwood on Jun 2, 2018 20:23:39 GMT -5
Just makeing a jet nozzle for this thing for testing racket suggested a 4in tube for my 89mm exducer im a liitle confused why it needs to be bigger than 89mm if its just getting brought back down at the nozzle to 77mm
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Post by racket on Jun 2, 2018 21:33:09 GMT -5
LOL...............if you can find an 89 mm ID tube ( ~92 mm OD ) by all means use it , I suggested 4" OD ~98 mm ID because of ready availability , we can always go bigger but never smaller than the exducer shrouds ID , we ideally want a smooth transition between shroud and jetpipe , the ~4.5 mm radial step for the 4" OD pipe won't make any difference
I'd suggest you try spooling her up without a jetnozzle until you get a feel for whats going on, the spoolup will be easier/quicker with less chance of a hung start and temps will be lower as well .
Cheers John
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