|
Post by smithy1 on Aug 31, 2021 18:14:09 GMT -5
Issues: The oil pump isn’t producing stable pressure with hot oil. If I let it idle after startup for a minute or so it’s fine but any more than that and especially if I start throttling it up, the low oil pressure switch pulses the fuel pump relay on/off rapidly causing a loss of throttle control. (Like the switch is dancing around it’s set cutoff) You mentioned a while back John about the lack of suction baffle, it’s hard to tell if it’s sucking air even with the clear suction hose so I think it would be wise to fit one. Also on the short drive down the road I made the oil tank breather spewed out oil all over one side of the combustion chamber. The road was fairly bumpy and the breather port is only ~3” from the oil level. Oil may have sloshed over the port and pushed out by the positive pressure. Time to fab up a catch can I suspect your oil is "foaming" in the tank....hence the spillage/spewing. An aeration plate in the tank where the oil returns to tank will help greatly.....and as John has mentioned, inlet and outlet at opposite ends or as far away from each other as possible will also help with cold/hot circulation issues. A breather and catch can is well recommended too. Smithy.
|
|
|
Post by smithy1 on Aug 10, 2021 23:30:36 GMT -5
I think that is the route I will go, also planning to include an oil cooler so I shouldn't have to worry about heat. What temp is best for the fan thermostat? Then again I guess that is dependent on the type of oil too. I had looked at some of the Chinese gear transfer/turbo scavenge pumps on ebay, they don't seem to have too much information on pressures and flow rates at different pressures Oil pumps can be of many different configurations, on my Go-kart an old early Subaru oil pump driven by an electric motor is used to great effect, John designed and built the one I have....and it still works fine to this day with no modifications by me. It happily supplies plenty of 70psi + oil pressure to my GT6041 106mm inducered turbo...it has never given the slightest hint of trouble after all these years. Usually our engines don't really run long enough to cause the oil to heat up to any great degree....also, oil temps can be dependant on oil tank quantity. I have ~7 liters capacity and use a passive oil cooler on mine and it has been fine for years. Oil temps never rise above ~90C even after several back to back engine runs within an hour... which is fine for most oils. Smithy.
|
|
|
Post by smithy1 on Aug 10, 2021 22:58:00 GMT -5
In that case max consume is 12,5 gph and whit afterburn even 50 gph, is that all 37,5 gph going to afterburner or can I spray more to flametube when I use afterburner, example 20 to flametube and rest 30 to afterburner? I know it was quite an old post but still may help if relevant... You're better of using two separate fuel systems, one for the engine itself and one for the afterburner, it makes controlling flows etc much easier. Also, when using a single system for both, when you open the afterburner to main engine fuel pressure will drop and cause rather large rpm changes....not always ideal when trying to get the best out of an afterburner. I have 4 fuel pumps on my go kart....the first is a "real" helicopter turbine engine fuel pump for the Garrett GT6041 powered engine and 3 x bosch 044 pumps for the afterburner...one of the three pumps is used for the hot streak, the other two feed the afterburner itself. I use the spray ring and "falme holder" method for mine...but the "Step pipe" method also works well. My little 1/4 scale jet dragster also uses separate pumps for the A/B and also uses a hot streak method of A/B ignition. John will verify all here as he's seen them both in action in person. www.youtube.com/watch?v=1XqoYhSxKCgwww.youtube.com/watch?v=rd_m9fItlN0And here is the little car doing a run during an "RC speed meet" at my now local drag strip several thousand years ago...clocked at just shy of 235kmh..! www.youtube.com/watch?v=jzYxMccS66cSmithy.
|
|
|
Post by smithy1 on Aug 10, 2021 22:39:38 GMT -5
Thanks I plan on having the oil pump powered by the boost itself. I notice nobody else has done this so im keen to do that. If you wish to use boost pressure to pressurize an oil tank to feed the bearings, you may want to think twice. Max boost pressure will be quite small if you keep it to 15-18 psi as John suggestes I'd imagine which would be marginal..... and only ~4-5psi @ idle....you'll need more oil pressure than that methinks. Smithy.
|
|
|
Post by smithy1 on Aug 10, 2021 22:18:22 GMT -5
|
|
|
Post by smithy1 on Jul 28, 2021 0:33:40 GMT -5
Thanks for the reply. To be honest my leaf blower barely spins it over its only a cheap one. Maybe like 1000rpm. The turbocharger seems in good condition, i mean its a journal bearing turbo so there is a fair amount of resistance. Is there no chance it will just gradually get itself going? No, 1000rpm is nowhere near enough on an engine that size...it will also have a bit more resistance with oil pressure too, the faster you can spin it the easier it is to get running and "over the hump". If you try to start with the rpm too low, it will just get hot. My 106mm inducered engine needs ~10,000rpm even before I think about lighting it up...it will self sustain at ~20,000 and idles nicely at ~25,000-28,000. Smithy.
|
|
|
Post by smithy1 on Jul 14, 2021 18:37:08 GMT -5
Hi Smithy How's QLD treating you ?? Good to hear the old girl is still performing :-) The 12/118 is sitting quietly on its trolley now that I've started work on the new engine , only room for one engine at a time on the test stand . Stay Safe Cheers John QLD is OK....miss Sydney though. Christine doesn't much like it as all the kids and grandkids are in Sydney. Haven't had much chance to run the old girl with this Covid crap killing all the car shows etc...I have a nice new mancave built now so If you're ever up this way...be sure to drop in. Smithy.
|
|
|
Post by smithy1 on Jul 14, 2021 17:08:26 GMT -5
I don’t know if I actually need 60ah worth of battery either. Just thought yeh that’ll be plenty. I use several RC Li-po batteries to power my setup. Different voltages for different purposes. My kart only runs for ~4-5mins at a time so no need for big A/H batteries. I mainly do static engine runs at car shows and school fetes etc... certainly draws a small crowd at most venues. John and I attended a Go-kart track to show off our machines a few years back...John's engine was certainly a beast and it was a pleasure to see it run in person..! Here's a vid of my kart at a small car show not far from Sydney a couple of years ago. www.youtube.com/watch?v=rd_m9fItlN0Smithy.
|
|
|
Post by smithy1 on May 11, 2021 21:57:21 GMT -5
I realized that I had forgotten to turn the oil pump on I shut it down as fast as possible but it was to late the bearings are cooked. An easy way to avoid this is to fit a "Hobbs" switch in the oil pump/fuel pump electrical circuit. This system won't let the fuel pump run unless there is oil pressure.... and when the engine is running, it shuts the fuel pump off if the oil pressure drops below the set point...which you can set to a safe desired pressure. It's a very simple solution to a potentially costly error. Smithy.
|
|
|
Post by smithy1 on May 11, 2021 21:43:31 GMT -5
I'd be keen to see your kart lifter mate..??
Smithy.
|
|
|
Post by smithy1 on Apr 19, 2021 22:40:51 GMT -5
I’ve started building a kart lifter as I’ll end up doing my back in getting it in and out of the trailer. Then I’ll get onto making an accumulator and getting some performance numbers on paper. I’m in Atwell, WA Have my hot streak is located in the combustion case, a stainless hard line going in through the lower half of the outer case and up between the outer case and the flame tube, it then bends 180 dergrees and goes in through the "hat" of the flame tube a few mm and points straight at the turbine inlet...it's a 0.8mm nozzle...2mm will be way to big. I have it running off an old VL commodore fuel pump via a normally closed solenoid and filter. I have two buttons on the steering wheel, one activates the A/B pumps, (two Bosch 044 pumps in parallel) and the other button activates the hot streak. I can manually vary the flow rates to suit what I want...they're basically just taps in the lines so I have infinite adjustability of their flows etc.... I adjusted the hot streak flow so I "JUST" get a lick of flame out the tail pipe when I hit the button. not enough and she won't light the A/B...too much and it's not real good for the turbine wheel. My pipe was modelled off Andy M's design. but he uses a different flame holder method to mine...mine is more conventional aircraftish with a proper flame holder with the spray ring up towards the turbine and flame holder several inches downstream of the spray ring...a bit of position "experimenting" is required to get the best out of them...but the results are worth it. So I can basically do the big white cloud of unburnt fuel...or I can light it up...just like the real jet dragsters do. Pity you're in WA....I couldn't be further away, I'm ~55km north of Brisbane. www.youtube.com/watch?v=rd_m9fItlN0Cheers, Smithy.
|
|
|
Post by smithy1 on Apr 14, 2021 0:43:29 GMT -5
Inconel 617 and 718 are both very "tough"...however, they don't like to be twisted too far or stress fractures will appear at the blade roots...been there done that.
As you mention, 718 is the better of the two, but 617 is fine for our DIY stuff.
Smithy
|
|
|
Post by smithy1 on Apr 13, 2021 22:21:05 GMT -5
Great work...nice to see another Aussie jet powered Go kart. With your A/B igniter...I tried all sorts like yours and others.... and finally went for a "hot-streak" system....works every time and is basically idiot proof.
As John mentioned, an accumulator in the upstream line to the injection will help wit "flameouts"....I have the same trouble with mine. As you've found out, slowly back on the throttle and it stays lit.
Whereabouts are you..??
Smithy.
|
|
|
Post by smithy1 on Feb 24, 2021 19:58:30 GMT -5
Hi Keith, Nice looking kart you have there....Here's a pic of mine for reference.. John was instrumental in the building of this kart...all I did was fettle it a bit... Smithy. Cheers smithy, glad I’m not the only one with a turbo that close to the seat. No mullets allowed 😂 did you make the front fairing? Looks great. Do you take it out much? I think you said a while ago you took it to a few car shows doing demos? Front fairings came with it...I believe it used to be a "Shifter Kart" and has front brakes as well as the single rear brake. I only do car shows with it these days as all the race tracks etc...wont allow such a vehicle on their tracks as it doesn't meet their "safety standards". My local drag strip wants a roll cage, 5 point harness, parachute and manual fuel shut-off etc etc... Cheers, Smithy.
|
|
|
Post by smithy1 on Feb 18, 2021 0:45:45 GMT -5
Thats some extensive r&d! Thanks for that info John. Never thought the offsetting would make such a difference in distance sprayed👌🏻 sweet, safe as is. I’ll mount the thermocouple and spray ring as picture and aim for those flow/pressure numbers. Keith Hi Keith, Nice looking kart you have there....Here's a pic of mine for reference.. John was instrumental in the building of this kart...all I did was fettle it a bit... Smithy.
|
|