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Post by racket on Aug 19, 2014 17:35:43 GMT -5
Hi Smithy
Heh , she'll be looking pretty sharp with those new wheels and rubber :-)
With a couple of 044 pumps mounted in that twin clamp and delivering fuel, her thirst will be more than satisfied , she's only a bit bigger unit to the 1/4 scale engine and your setup on her A/B is a joy to watch and "feel" when in action, ...........LOL, the "pops" will be a tad louder though ...........I'll be looking forward to seeing some video of her "smokin' and popping" and you with a big grin on your face loving every minute of it as you scare the little kids .
Cheers
John
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Post by smithy1 on Aug 19, 2014 17:56:19 GMT -5
Hi Smithy Heh , she'll be looking pretty sharp with those new wheels and rubber :-) With a couple of 044 pumps mounted in that twin clamp and delivering fuel, her thirst will be more than satisfied , she's only a bit bigger unit to the 1/4 scale engine and your setup on her A/B is a joy to watch and "feel" when in action, ...........LOL, the "pops" will be a tad louder though ...........I'll be looking forward to seeing some video of her "smokin' and popping" and you with a big grin on your face loving every minute of it as you scare the little kids . Cheers John Yup...LOL...looking forward to making a bit of smoke, fire, noise and corruption. You said... "only a bit bigger unit to the 1/4 scale engine"....Pffttt... hardly  The 6041 and it's mass airflow is huge in comparison, can't wait to make some "music" with it..! I find it's the "big" kids who get scared as well as the little ones..! Nothing better than scaring the crap out of some nucklehead who thinks my little dragster is a "toy"..!  The new rear axle center bearing and mount just arrived this morning too, I'll see if I have enough time to fit it and get the rear axle cut and sorted by the weekend, time might be a bit tight though..! Progress is happening..! |
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Post by racket on Aug 19, 2014 20:10:02 GMT -5
Hi Smithy
Yeh , the older guys take the "mandatory" step or two backwards whilst still trying to look "cool" about the whole business.
I did some "numbers" for the engine using your TOT of 630 deg C at 35 psi P2 - 3.38 PR , efficiency of the comp should be 75% according to the map , so a temp rise of ~160 deg C , this'll need ~140 drop through the turb , so a T I T of ~770 C , nice and cool.
The turbine map gives a corrected max flow through the turb stage of ~95 lbs/min at ~3:1 PR , there will hopefully be a PR of ~3.2 :1 going in if theres a 5% pressure drop across the combustor , the turb map is pretty flat once past a 2.5 :1 PR , if we do the maths to find an actual flow at your temps and pressures going into the stage the actual flow comes in at ~160 lbs/min - 2.66 lbs/sec, virtually spot on the best flow at 35 psi P2 ...........lookin' good :-)
I had a few problems trying to workout what was happening once the gases were in the "jetpipe" because of the large A/B jetnozzle , theoretically there should have been a PR across the turb stage of ~2.1:1 to power the comp leaving an ~1.52 PR - 7 psit in the jetpipe which should have produced a velocity of ~1450 ft/sec and ~120 lbs of thrust with a correctly sized jet nozzle , but with that big afterburning sized jet nozzle I'm not sure what the velocity/thrust would have been, maybe the A/B nozzle has a large velocity gradient across it, don't know :-( ..............at least the "choking" turbine stage is keeping mass flow under control.
It'll be interesting to see what numbers you get with the A/B alight and burning a full load of fuel, ......I'll make a guess at 10 psit in the A/B at a TOT of 750 C .
Cheers
John
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Post by smithy1 on Aug 19, 2014 21:13:54 GMT -5
Hi Smithy Yeh , the older guys take the "mandatory" step or two backwards whilst still trying to look "cool" about the whole business. I did some "numbers" for the engine using your TOT of 630 deg C at 35 psi P2 - 3.38 PR , efficiency of the comp should be 75% according to the map , so a temp rise of ~160 deg C , this'll need ~140 drop through the turb , so a T I T of ~770 C , nice and cool. The turbine map gives a corrected max flow through the turb stage of ~95 lbs/min at ~3:1 PR , there will hopefully be a PR of ~3.2 :1 going in if theres a 5% pressure drop across the combustor , the turb map is pretty flat once past a 2.5 :1 PR , if we do the maths to find an actual flow at your temps and pressures going into the stage the actual flow comes in at ~160 lbs/min - 2.66 lbs/sec, virtually spot on the best flow at 35 psi P2 ...........lookin' good :-) I had a few problems trying to workout what was happening once the gases were in the "jetpipe" because of the large A/B jetnozzle , theoretically there should have been a PR across the turb stage of ~2.1:1 to power the comp leaving an ~1.52 PR - 7 psit in the jetpipe which should have produced a velocity of ~1450 ft/sec and ~120 lbs of thrust with a correctly sized jet nozzle , but with that big afterburning sized jet nozzle I'm not sure what the velocity/thrust would have been, maybe the A/B nozzle has a large velocity gradient across it, don't know :-( ..............at least the "choking" turbine stage is keeping mass flow under control. It'll be interesting to see what numbers you get with the A/B alight and burning a full load of fuel, ......I'll make a guess at 10 psit in the A/B at a TOT of 750 C . Cheers John Yep, those numbers look pretty close to mine  , (give or take my errors), although I'd trust yours before anyone else's. Assuming the temps will remain fairly constant above that, (within reason), I'm suspecting going to a P2 of ~38psi will see the PR at ~3.58 and efficiency will start dropping off significantly after that??, Your thoughts??....I suspect we'll essentially be beating the air to death for very little or no gain, although the comp map suggests we can go significantly higher and still be ok...I'm guessing the rpm will be significantly higher than 77k by the top of the map  , that's a lot of rpm for such a big impeller of 141mm exducer. The turbine map is indeed fairly flat after 2.5-2.6PR and only goes to 3 so I'm guessing the efficiency of ~78% slowly falls off after that. By my numbers and with the theoretical number of 1.52PR after the comp has taken what it needs we should be seeing ~7.6psit in the pipe, not too bad to be honest, but I suspect there will be losses I haven't factored in. 1450ft/sec velocity from the jet pipe is indeed getting pretty high....hopefully the flame holder can do exactly that....hold a flame, I have no doubt it will at much lower P2's and velocities but when those velocities get up ~400ft/sec+ she's getting a little windy through there..! I doubt holding a lit match in there will help much! . Hopefully the hot-streak I've made and your flame holder will do their job. Assuming ~30% increase in thrust during A/B, I'm guessing a wet pressure of~9.88psit..! We'll soon find out..! Cheers, Smithy. |
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Post by racket on Aug 19, 2014 23:11:24 GMT -5
I once did some calcs for higher rpm, and yes, the thrust levels don't increase much , the comp efficiency does start dropping off but the small increases in thrust are mainly because the mass flow hardly increase due to the inducer choking from excessive tip speeds, theres sonic shock problems at the inducer tips once past ~60,000 rpm because of the 56 Trim wheel , at 60,000 rpm the inducer tip is going at ~1310 ft/sec , add on some extra relative velocity for the ingoing air and those tips are going supersonic by a big margin .
The wheel has a lot of exducer swept back compared to our TV94 wheels , ~60 degrees vs ~75 degrees so the peak pressure is less for a given rpm but it makes up for it with better efficiency , its best performance is probably in that 63 -68,000 rpm range , which leave an ~10,000 rpm buffer before reaching the map top rpm line at ~78K where the tip is going at just under 1,900 ft/sec , though the wheel is probably still "safe" to well over 2,000 ft/sec ............heh heh , that comp housing has very thick walls for good reason :-)
You should only have ~400 ft/sec gas velocity at the flameholder , I think I calculated an exducer exit axial velocity of ~700 ft/sec , the diffusing cone downstream of the exducer should slow it down to the 400 , hot streak should work just fine :-)
I've read that turbine efficiency gets better with blade speed, .... but a point is reached where the gas velocity comes into it and there needs to be a "balance" , the GT6041 turb wheel is of the "modern" high pressure ratio type designed for going fast , we can probably use the 78% for our calcs without being far wrong .
Cheers
John
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Post by smithy1 on Aug 20, 2014 3:18:45 GMT -5
Thanks for the confirmation John...really appreciate the time you take to help all of us...I hope I don't ask too much of you..??
On a side note....I fitted the new Dunlops to the new magnesium rims this arvo, after a bit of arguing they went on fairly easily with the right "technique".... all good so far and the new fronts are actually on the kart. I currently have the solid rear axle out of the kart so I can modify it to fit the new bearing assy.... so it'll essentially have a pair of free wheeling wheels..! It should turn easily now rather than "understeer"...all the weight over the rear end doesn't help either.... Should work fine, I hope.!
I'm also in the process of making a couple of "Y" pieces to connect two A/B pumps, both upstream and downstream of the pumps. I think there may be a small restriction with the single feed line but I can do some testing to see if it causes any drama. I believe the original hose is 3/8" ID so it should be enough, if not I'll just go up a size to 7/16"...just a 40% increase in ID will give me double the area so maybe the next size up hoses will suffice if the 3/8" isn't enough.
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Post by racket on Aug 20, 2014 4:36:11 GMT -5
LOL.....no trouble at all :-)
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Post by madpatty on Aug 20, 2014 13:21:07 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. Hi Smithy, mind if you can give me some details on the motor you are using or have used to spool your engine at some point of the time...obviously its a castle creations 1717 but as far as i have come to know from the internet it is no longer available...some new models have taken its place.... i wanted to know how much rpm it was able to reach while spooling the rotor and what power it used to run at...some details on the battery voltage you used... actually i will also be considering electric start if that blower thing doesn't settle out...some motors with comparable specs were available at 1/3rd the price at hobby king....see the link(http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=21969).....is the one in the link close to your motor spec wise?? thanks, Patty |
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Post by smithy1 on Aug 20, 2014 15:24:23 GMT -5
Hi Smithy, mind if you can give me some details on the motor you are using or have used to spool your engine at some point of the time...obviously its a castle creations 1717 but as far as i have come to know from the internet it is no longer available...some new models have taken its place.... i wanted to know how much rpm it was able to reach while spooling the rotor and what power it used to run at...some details on the battery voltage you used... actually i will also be considering electric start if that blower thing doesn't settle out...some motors with comparable specs were available at 1/3rd the price at hobby king....see the link(http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=21969).....is the one in the link close to your motor spec wise?? thanks, Patty Hi Patty, I still have the Castle 1717 motor... and yes, I believe it has long ago been discontinued by Castle, the one you link to at HobbyKing is actually a larger capacity motor than the 1717. It's max rating of ~6kw should be plenty, although I think they may be a tad optimistic..! The 1717 is rated at a tad over 3kw, but I've heard of guys running them much harder than that. I ran the 1717 (which is 1580kv) on a 4 cell 5000mah 45c Li-Po, (14.8v nominal), giving a no load RPM of over 23,000rpm, When testing the 6041 setup I was able to get a loaded rpm of just shy of ~8000rpm which is plenty to get the 6041 up and running even with 70psi oil pressure.....when she lights up the load reduces significantly and getting over the hump should be easy. If I recall correctly the 1717 was pulling a maximum of ~100amps on the "hit" during my testing, the current draw quickly tapered off as the rotor rpm increased and the load dropped off, this equates to a maximum of just 1.480kw, which I believe was plenty at the time. The 6041 will actually self sustain at quite a low rpm, well below 20k but as John suggests, is happier idling @ ~29-30k or ~4.5-5psi P2 or a PR of ~1.33-1.34 and flowing ~70lbs/min. With your setup being quite a bit smaller than the 6041, I doubt you'll need such a big brushless motor but it will certainly do what you need. The 6041 also is a very free running turbo compared to most... even with plenty of oil pressure. The same can't be said of many other turbos. The motor you are suggesting has a rating of 1740kv and will be more than enough for your requirements. Experimenting with different battery voltages is probably the way to go, but given the kv of the motor and with a no load rpm of 25,752rpm on just a 4 cell Li-Po, I'd suggest starting with that....these brushless motors can be quite hungry during a hard pull.... and will pull plenty of current so be sure to allow for that with your setup. Over-engineer your speed control current capacity, battery current capacity & wiring by ~30% and you should be good to go. Cheers, Smithy. |
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Post by smithy1 on Aug 21, 2014 3:24:51 GMT -5
Hi All, Just finished the rear axle mod and fitting of the new wheels & tyres, also the "Hot-Streak" solenoid and activation switch installation.... here's a couple of photos: Nice new wheels and tyres.  Hot streak solenoid & plumbing.  Hot streak line going into tertiary area of CC.  A/B activation button on left, hot streak on the right, I've wired it so they can be activated independently of each other. Which means lots of white smoke if I choose.  |
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Post by racket on Aug 21, 2014 4:12:39 GMT -5
Hi Smithy
Lookin' good :-)
Cheers
John
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Post by enginewhisperer on Aug 21, 2014 4:43:51 GMT -5
good stuff! I should be there on Sunday  |
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Post by pitciblackscotland on Aug 21, 2014 7:36:49 GMT -5
Hi Brett,
Thanks for the photos, good to see this beast again :-) Hope you have a good run on Sunday.
Cheers,
Mark.
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Post by Richard OConnell on Aug 21, 2014 8:36:16 GMT -5
Nice setup, what are you using as a hot streak timer?
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Post by smithy1 on Aug 21, 2014 14:40:13 GMT -5
good stuff! I should be there on Sunday Excellent...I look forward to seeing you there....hopefully the weather will be kind to us, (if it's raining I wouldn't bother). I won't be doing any "driving" of the kart, will only be doing some static engine runs and a few A/B pops etc, will actually be the maiden run of the hot-streak system . The car show is in the car park of a small-ish shopping center so not a lot of room to play.... Cheers, Smithy. |
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The 6041 and it's mass airflow is huge in comparison, can't wait to make some "music" with it..! I find it's the "big" kids who get scared as well as the little ones..! Nothing better than scaring the crap out of some nucklehead who thinks my little dragster is a "toy"..! 
, (give or take my errors), although I'd trust yours before anyone else's. Assuming the temps will remain fairly constant above that, (within reason), I'm suspecting going to a P2 of ~38psi will see the PR at ~3.58 and efficiency will start dropping off significantly after that??, Your thoughts??....I suspect we'll essentially be beating the air to death for very little or no gain, although the comp map suggests we can go significantly higher and still be ok...I'm guessing the rpm will be significantly higher than 77k by the top of the map 
, that's a lot of rpm for such a big impeller of 141mm exducer. 
