Hi was wondering what people are using for easy access to make flame tube and combustion chambers out of, so far all i could think of is fire extiguisher bottles, accetylin/oxygen/propane bottle tanks, 5" to 6" muffler pipe which seems rare at most auto places, and plumbing pipe but thats super heavy. Anyone else know any other things that are easy to access and not to pricey. Dont feel like rolling and welding any sheet steel for the tubes. Seems like i need to find 6" to 7" due to the fact people on here are saying 3 times the inducer area is better than twice the inducer, which means i have to use a smaller turbo around only 2" diameter to acheive the 3 times bigger rule everyone is talking about, seems like i cant go bigger than 2", i wantes to use a 3" inducer sized turbo but 3 times bigger than that means i need 9" flame tube which is huge and without rolling the tubes myself, it will be hard to find premade tubes thatbare easy to find that are that big, would be nice to do the 2 times bigger rule so i can use a 3 inch inducer turbo and get away with a 6" diameter flame tube.
I guess you haven't read my reply of yesterday giving you a Link to data here on JATO.
When we talk about ratio of inducer to flametube AREAS its a lot different to DIAMETER ratios .
If you use Jetspecs it'll use diameters so that guys don't need to do the maths working out areas, and theres a 3X for small turbos because they don't use high pressures whereas larger turbos it uses 2X because they can .
Post by adamrenwald on Aug 12, 2022 3:10:20 GMT -5
Oh ok, thanks for clearing that up, i spent like 3 hrs yesterday skimming through all the posts and found someone who mentioned about that too that for the small engines to use a 3 times bigger than inducer size but i kept hereing allot of other people to say stick with 3 times rule, wasnt sure how it is for the bigger engines, well than that is allot better than for me because i was hoping to find a turbo that has a inducer diameter of 2 1/2 or 3" :]
Hey racket, so it nice that it seem like once you get a little bigger on the turbo inducer size that it doesnt even got to be quiet the 2x the size rule anymore because in that last paragraph you stated that you can use a 3" inducer size and get away with a 5.2" diameter flame tube which is less than the 2x rule, im still lost on all the area times area mumbo jumbo, my brain is bad at that kinda math sometimes, i like the simple induser size rule better, i know its probably not as good but for me its better as of now :] so would it be better thow if i used a 6" diameter for a 3" inducer size, or since its bigger it doesnt need to and maybe overkill? I like the 5" diameter size better anyway because i found a perfect 5" diameter fire extinguisher that also is a little longer than the 6 times the inducer size for the lentgh, so that will be easy accessable, and im not sure where to get a 7" diameter fire extinguisher. That seems huge, maybe gotta order it online or maybe see if i can get a hold of a oxygen tank thats not to thick on the casing. So i think 5" for flame tube is perfect and 7 inch for outcase which leaves a 1" space inbetween which would seem fine. I beleive i read on here that 1/2 to 3/4 spacing is preffered but 1 inch shouldnt be that bad for something that big im guessing, so now i need to be on the hunt for a turbo and wondering if i should go with a 3" inducer or 2 1/2", 2 1/2" would keep me at the 2x as large rule but like i said im not sure if that matters anymore since you said that for a 3" you can go smaller than 2x rule, i guess thats why i need learn that mathmatical area equation but ill save that for another day. So not sure if at that size it benefits keeping that rule or is just over kill and id be better off using the 3" size turbo. I do like the bigger size because i want more thrust and to beable to blow more air out of the exhuast but the only thing i wanna factor in before i pick is that i also want to get a good amount of run time out of my 20lb propane tank, i know they both will probably consume fast but is there a big difference? Im hoping to get at least 20 mins at different power settings from the 2 1/2" size turbo,probably will run it to full power for short bursts and come back down to idle and back and fortg ,probably wont be pinning it full power for long periods of time, so hoping to get 20 mins at least out of that kind of running. Im lookin at turbos now, you think id be better of with the 3"?
Combustors are a "complex" issue , lotsa variable , thats why Jetspecs was conceived to "simplify ?? " the process , its a crude device that should produce a working engine , whereas if more thought and consideration to fuel and air presentation the size can be reduced considerably , as an example , my 12/128 engine has a flametube only as long as the inducer is wide , BUT , its crossectional area is 3X inducer area , its hard to skimp on the crossection without lotsa problems unless we use higher pressure ratios from the comp .
A flametube can be grossly oversized without causing any big problems, but even the smallest amount undersized and we're in trouble .
If using a 20 lb propane tank for "gasious" fueling the engine , you'll have problems with anything bigger than an ~2" inducer, the vapour pressure in the cylinder drops too quickly as it starts to "freeze up" as fuel "boils off" .
The 7" fire extinguishers are "air over water" types used on wood/paper fires, very lightweight but safety tested for 100psi , so make great outer cans .
20 minutes is a long run time , it won't be possible unless you use a pretty small turbo if using propane .......................what do you want to use the engine for ??
If for a mobile unit then you'll need the mass flow of a largish turbo , but then your fuel burn is higher ................so I'd suggest getting this sorted first before looking at turbos .
Hi john, thanks for the advice, well that was a big mystery question, so with knowing that about the fuel consumption rate, maybe ill just search for a 2" diameter turbo. My goal as of now is just to make a working jet engine that makes a good amount of air blowing out the exhuast so when i run it and show it to people i can use it like a leafblower on steriods :] just want it to run and not melt tge turbine, i allready built a working one that went to power pretty good but the life was very very short,turbine blades melted, so i feel like redoing the flame tube is what will fix it, as long as it runs and doesnt melt, im happy. I can watch it run all day as i just like the science of how things work and thats what makes me interested, im sure later on once im hooked ill probably want to do more with it like put it on a gocart, i use to hava 80lb thrust valveless pulse jet on one but it ate the fuel supper fast, i kinda want a engine with more run time even if i gotta sacrifice thrust, only thing im wodering now is if a 2" turbo has way skinnier turbine blades than say 2 1/2 or 3" inducer size one, because that was originally why i thought mine melted because i was using a 1.5 size one, it was really tiny but maybe it was all just because of the flame tube being wrong, bjt i have heard the little ones are more fineky, so 2" size would kinda be in the "medium sizeed" engines?, i guess ill look for a 2 1/4 sized one or somethin than idk.
Im looking at some t3 t4 turbos on amazon but after some reading on here im assuming its not good since people are saying the turbine shoukd be same or 15 to 20% bigger than compressor, i think from what i gathered t3 t4 turbo means the turbine is smaller than compressor so i got that oyt if the way in my search but im wondering about the turbos with the extra hokes around the fromt of the intake for surge protection, im not sure if that would be a problem but im assuming its better to have all the air directlt conpressed into the comubustion chamber so having those surge holes in there would not be good? Just my guess, should i not get one with that on the turbo, i just want a oil cooled journel bearing one woth no kinda waste gate, just not sure about surge protection holes
Yea i was looking a that exact turbo, i like iy because it looks simple, i like how it has the 4 bolt pattern on the end so you can easiky weld a tube to a flange that will bolt right on and bo wastegate thingy majig, well for some reason i cant down load jet specs on my phone so im jjst going to stick with the 2.5" inducer sixe because i found a allready filled out jetspecs sheet that has all the sizes of drill bits to use and for how many holes it req on the flame tube and its for a 2.5 size inducer. My only problem is that on somenof the amazon turbochargers specs, it only say a/r ratio and not the size of the inducer, some have it and some dont, if im looking for a 2.5" inducer size and all i see for the specs on the turbo charger is the a/r ratios so i dont know how to figure out what inducer size it is if it doesnt allready show the size under the specs.
This engine self sustained great, ran up to what seemed like allot of power and than after about 8 seconds it sput out sparks and flamed out, i noticed there was some lining inside the shroud that started melting off like it was a different material than the cast of the turbine shroud, it started pealing towards the turbine like skin pealing of the metal but it was like a metal skin and i beleive that rubbed against the turbine and cause the blades to get shredded