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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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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 smithy1 on Aug 20, 2014 19:30:39 GMT -5
Hi Smithy, These are 6901 size bearings: 12mm X24mm X6mm. Even though it is a "standard" bearing, it isn't as common as others. -Ash Thanks Ash..I'll have a look at the ones I have at home, (am at work atm), I repaired an old AMT Olympus engine some time ago and have some bearings for it, but can't recall the exact size of them....they were larger than the normal 608 type which are 8 x 22 x 7 used in most mid-large size RC turbines these days. No promises though.... but it can't hurt to have a look. Cheers, Smithy.
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Post by smithy1 on Aug 20, 2014 16:18:15 GMT -5
Hi Ash, Can you give me the dimensions of your bearings?....I "may" have a couple of full compliment ceramic ball items here which could be of use to you.
Cheers, Smithy.
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Post by smithy1 on Aug 20, 2014 16:06:57 GMT -5
Hi Anders, Impressive looking steam turbine..!
I watched your bike videos last night....excellent work indeed...!
You like Top Fuel Dragsters eh??...I crewed on several of them here in Sydney for ~7-8 years on & off...They're silly machines really, ~7000hp+ & drinking ~8 liters of nitro per second..! Listen closely when they go into the first stage light, you'll hear them go onto full fuel delivery, the sound changes significantly. Also listen closely to them as they go down the track you can just tell when each phase of the hydro-pneumatic/centrifugal clutch is engaged as the rpm fluctuates slightly..they "should" be on full clutch lock-up by around 1/2 track if running the full 1/4 mile.
When standing behind them on the start line, we used to get "rained on" by all the unburnt nitro from the exhaust...how they run with an air/fuel ratio of just 1.8:1 is beyond me..! I guess running twin spark plugs at 44amps in each cylinder helps..!
Cheers, Smithy.
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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 20, 2014 3:35:40 GMT -5
Thanks Anders, All understood....more photos won't be necessary, I just needed an idea of what's required.....I plan to do the something similar to the GT6041 powered "Green Beast"..! It's an ideal way to read rpms for our machines with an "off the shelf" item...a cheap tacho like the one you have from fleabay can be had for less than $15..!
Excellent work Sir.
Cheers, Smithy.
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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 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 smithy1 on Aug 19, 2014 20:17:50 GMT -5
Hi Anders, Great work..! A question if I may....I see you're using one of the reflective type tachometers, can you please tell me how you have the pick-up mounted in the compressor housing, or have you just got it pointing at the wheel?? A photo or two would be greatly appreciated.
I'm thinking of using a similar method for the 6041 "Beast".
Cheers, Brett.
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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 smithy1 on Aug 19, 2014 17:01:40 GMT -5
Hey Patty, John is spot on here.....I play with miniature RC turbines all the time and they do indeed spool up very easily....and as John mentions, they have nice free running full compliment ceramic bearings.....they essentially have no drag compared to a turbo type oil pressure reliant floating bushing setup. I have one propane start 8kg thrust engine which spools up to idle in ~8-10 seconds after start initiation, the engine in my 1/4 scale after-burning dragster is now a full kerosene start engine and needs ~7-8 seconds just to heat the ceramic glow element for ignition, then it's a smooth spool-up to an idle of 33k from there, the whole process takes ~30seconds.
As John mentions, keep just enough fuel going to keep the flames at bay and plenty of starter into it until she gets "over the hump". If this fails then there's obviously something amis inside.
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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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 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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