ThunderTiger
Hardcore RCTalk User
amen to that !!!!
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moe7404
Hardcore RCTalk User
Military Veteran
- Thread starter
- #42
well i dont reay like my supercharger fro R.B. it is hard to tune. i was already thinking about geting a 3 neddle carb. i was thinking of mixing high nitro % to make up for the SC. but then i thought about that old saying " change only one thing at a time"
ThunderTiger
Hardcore RCTalk User
therein is the problem. to get the performance from the SC, you have to buy other parts/products you would otherwise not need.
In short, remove the SC and just run a higher nitro content or fit a BB engine instead of wasting the money on an RBI SC.
I learnt the hard way, I will not be making the same mistake again.
In short, remove the SC and just run a higher nitro content or fit a BB engine instead of wasting the money on an RBI SC.
I learnt the hard way, I will not be making the same mistake again.
revo_rob_1984
OverMedicated
Supporter
As have i made the same mistake, if i could turn back time i would have just bought the engine instead of the supercharger
moe7404
Hardcore RCTalk User
Military Veteran
- Thread starter
- #45
well thunder iam glad you gave me some pointers, i may try them out. but like you said its a bitch to tune. i was just running it. i had to keep ajusting the fuel, finaly on the third tank when i ask for full power it just died. i have never have had one die asking for full power. my hi speed was 3 1/2 or 4 turns out. i allmost got the idle dead on. part of the time i had 0 % nitro 14% oil, and 40% nitro, could not tell much differance. then i fliped it, and bent the supercharger bracket. it just came to me real superchargers have the throttle plates ABOVE the supercharger.
No way! 5-6psi would be a substantial increase in power. I doubt you get ANY noticeable pressure with these systems. BTW,how much did you overdrive the sc?
They run them both ways. Draw through carbs to me seems like would be easier to tune.
Anyone want to sell me one cheap? I have a design started for a compressor and housing to make one that will make boost. I would like to have one of these for comparisson and fitment/modification purposes..
Lessen
Super Awesome!
Supporter
Yep, I was gonna say the same thing. We used to have a Volvo S60 which had a turbocharged 5-cylinder. I think the turbo was right around that pressure. I'm pretty confident about that number because I remember reading some literature on the S60R which had the same powerplant except with a high pressure turbo. I believe the "R" version of the car ran like 8psi or something around there. So yeah, 5-6 psi of boost is pretty freakin' significant.
ThunderTiger
Hardcore RCTalk User
Moe, Racer 7 lessen, the point i was making, which i seemed clearly to have missed, is that there is no visible OR audible power differential and that no boost is evident at all from the SC. Therefore, the figure quoted was of little importance (or accuracy) and merely a means to making a point.
As a point of interest, has anyone tested an RBI SC on a pressure gauge through the RPM range of a nitro engine both on the standard pulley and the overdrive pulley? (3 - 38,000rpm is the max i have so far seen)
Racer 1966: The best form of "compressor" type supercharger is that of a 5 fin 3/4 turn or 5 fin 1 turn screw (alternatively, 6 fin would be suffice). One male and one female screw (if i remember rightly the female has anti clock fins whilst the male screw has clock wise rotating fins). It is more than enough to create the boost so required. There is also the fact that you would need only one pulley to drive it due to the ability to gear the back end to run each screw in an opposing direction to the other by the simple fitment of two same tooth count gears (remembering of course to first set tolerances, and key the gears to the shaft for alignment of said clearance). Depending on the minimum required boost level and the maximum boost level so desired from the "compressor" supercharger would determine the overall size of the screw fins let alone the number required. the minimum/maximum size for the draught (air input) and exhaust (air output) throat size is one for experimentation or serious mathematical analysis. once those factors have been calculated, the rest is a case of design, trial manufacture, tolerence setting and trial application testing.
As an aside, there is a point at which more fins becomes less efficient due to the fin sizes encountered. This aspect would therefore need careful analysis and calculation for maximum air volume at maximum rpm, or to term it in compressor speak "Cubic feet per minute" (CFM) at maximium rpm.
Having looked at this myself some time ago, i became convinced that the screw type supercharger is the most efficient way to gain the boost, using the least componants whilst utilising the lightest, yet strongest material available for the task, especially having prior experience of working with compressors.
There is also the option of a vein type compressor that runs in an ovalised cylinder thereby acting to draw in air as the veins ride the oval side of the cylinder, pull it through with the veins (blades), compress it and throw it out the other side. (air tools are mainly run via vein type setups)
As to efficiency ? the screw compressor type supercharger would be the best all around option due to the nature of the design.
AS to which method is best, i am uncertain of whether a draught through supercharger (super charger under the carb) or a blower supercharger (supercharger over the carb) would be best. only application testing will confirm or disprove each theory. either way, i still remain convinced that some form of extra fuel pressure would be required to meet the demands placed on the fuel delivery system. I.E, lack of fuel delivery pressure would result in fuel starvation and lack of correct performance from the engine.
During the time i actually worked with compressors, the screw compressor was always proven to be the most efficient, the least hassle to maintain and the easiest to service purely by the nature of it's design.
Why a screw type over a vein type SC ?? a vein type SC requires more specific and certainly more regular service intervals to ensure peak performance form the unit itself because of the veins which in time wear considerable faster in comparison to a screw compressors fins.
As a point of interest, has anyone tested an RBI SC on a pressure gauge through the RPM range of a nitro engine both on the standard pulley and the overdrive pulley? (3 - 38,000rpm is the max i have so far seen)
Racer 1966: The best form of "compressor" type supercharger is that of a 5 fin 3/4 turn or 5 fin 1 turn screw (alternatively, 6 fin would be suffice). One male and one female screw (if i remember rightly the female has anti clock fins whilst the male screw has clock wise rotating fins). It is more than enough to create the boost so required. There is also the fact that you would need only one pulley to drive it due to the ability to gear the back end to run each screw in an opposing direction to the other by the simple fitment of two same tooth count gears (remembering of course to first set tolerances, and key the gears to the shaft for alignment of said clearance). Depending on the minimum required boost level and the maximum boost level so desired from the "compressor" supercharger would determine the overall size of the screw fins let alone the number required. the minimum/maximum size for the draught (air input) and exhaust (air output) throat size is one for experimentation or serious mathematical analysis. once those factors have been calculated, the rest is a case of design, trial manufacture, tolerence setting and trial application testing.
As an aside, there is a point at which more fins becomes less efficient due to the fin sizes encountered. This aspect would therefore need careful analysis and calculation for maximum air volume at maximum rpm, or to term it in compressor speak "Cubic feet per minute" (CFM) at maximium rpm.
Having looked at this myself some time ago, i became convinced that the screw type supercharger is the most efficient way to gain the boost, using the least componants whilst utilising the lightest, yet strongest material available for the task, especially having prior experience of working with compressors.
There is also the option of a vein type compressor that runs in an ovalised cylinder thereby acting to draw in air as the veins ride the oval side of the cylinder, pull it through with the veins (blades), compress it and throw it out the other side. (air tools are mainly run via vein type setups)
As to efficiency ? the screw compressor type supercharger would be the best all around option due to the nature of the design.
AS to which method is best, i am uncertain of whether a draught through supercharger (super charger under the carb) or a blower supercharger (supercharger over the carb) would be best. only application testing will confirm or disprove each theory. either way, i still remain convinced that some form of extra fuel pressure would be required to meet the demands placed on the fuel delivery system. I.E, lack of fuel delivery pressure would result in fuel starvation and lack of correct performance from the engine.
During the time i actually worked with compressors, the screw compressor was always proven to be the most efficient, the least hassle to maintain and the easiest to service purely by the nature of it's design.
Why a screw type over a vein type SC ?? a vein type SC requires more specific and certainly more regular service intervals to ensure peak performance form the unit itself because of the veins which in time wear considerable faster in comparison to a screw compressors fins.
Last edited:
moe7404
Hardcore RCTalk User
Military Veteran
- Thread starter
- #49
well i thank you all for your ideas. i havent started to repair the bracket yet. i was wandering if the sc could be "blue printed" like one does to a street engine. i havent yet decieded if ill keep the sc or not.
ThunderTiger
Hardcore RCTalk User
I never did understand the term "Blueprint" in relation to an engine.......................
As to the RBI SC, unless you are prepared to design and manufacture a housing to fit and tig weld INSIDE the RBI SC to enclose the outer diameter of the "fan" and direct the so called "compressed" air smoothly to the exhaust side of the unit, there really is little else to do but take it off.
Alternatively, blank of the exhaust side of the SC and utilise the pressure line from the SC to go to the fuel tank along with the pressure line from the exhaust, whilst also fitting non return valves in the line to stop pressure bleed off.
It will certainly give a more consistent fuel delivery through the RPM range and give more consistent throttle response and more equal power due to the boosted fuel delivery pressure, which is where a regularly aspirated fuel delivery system of a nitro engine falls flat.
That said, even the fitment of a Non return valve (alternatively known as a one way pressure valve) in the exhaust pressure line would stop pressure bleed off on releasing the throttle, which is where a nitro engine loses most of its consistency in fuel delivery.
As to the RBI SC, unless you are prepared to design and manufacture a housing to fit and tig weld INSIDE the RBI SC to enclose the outer diameter of the "fan" and direct the so called "compressed" air smoothly to the exhaust side of the unit, there really is little else to do but take it off.
Alternatively, blank of the exhaust side of the SC and utilise the pressure line from the SC to go to the fuel tank along with the pressure line from the exhaust, whilst also fitting non return valves in the line to stop pressure bleed off.
It will certainly give a more consistent fuel delivery through the RPM range and give more consistent throttle response and more equal power due to the boosted fuel delivery pressure, which is where a regularly aspirated fuel delivery system of a nitro engine falls flat.
That said, even the fitment of a Non return valve (alternatively known as a one way pressure valve) in the exhaust pressure line would stop pressure bleed off on releasing the throttle, which is where a nitro engine loses most of its consistency in fuel delivery.
Geesh TT, that was a bunch of typing.
Simply put, in this scale the twin screw compressors are too intricate to machine and set up as are the vein or "roots" stlye as we call them in the US. What I have in mind is a turbocharger style compressor and housing. The RBI is basically a turbo stlye, just not effective.
Simply put, in this scale the twin screw compressors are too intricate to machine and set up as are the vein or "roots" stlye as we call them in the US. What I have in mind is a turbocharger style compressor and housing. The RBI is basically a turbo stlye, just not effective.
ThunderTiger
Hardcore RCTalk User
CNC machining is the answer to the conundrum of a screw type SC. No matter what the size.
The compressor company over here that manufactures and sells screw compressors actually MAKES miniature versions of the screw head itself as a demonstration piece..............
The compressor company over here that manufactures and sells screw compressors actually MAKES miniature versions of the screw head itself as a demonstration piece..............
No offense but, DUH!!!!!!!!! I have a full machine shop to use.
ThunderTiger
Hardcore RCTalk User
how am i meant to know that you have a full machine shop ???
And why do take the attitude you have ? there was no need for the "DUH!!!!!!!!!" comment.
If you treat people with that attitude, i'm sure they wont be as forthcoming with information in the future. I simply pointed out that CNC machining is the answer to machining a screw, you come back with that attitude ??
This would have been more than adequate as a response >>> "No offense, but I have a full machine shop to use."
Don't get your panties in a wad,there was no attitude. If there was I was have said Duhh!! and left it at that. The "I have a full machine shop to use " was informational only.
Even if I didn't have a shop to use, most people know a cnc is how things are made. Nearly every custom part you buy says cnc on the box.
Even if I didn't have a shop to use, most people know a cnc is how things are made. Nearly every custom part you buy says cnc on the box.
moe7404
Hardcore RCTalk User
Military Veteran
- Thread starter
- #56
hey guys you both are my buds, i dont want to see an argument. i just wish i had a shop like racer. i was a machinist for 32 years, but never got to run a CNC. when i first went to Boeing in 1979, i ment a guy running a NC, he could NOT edit ANYTHING. if somethig was wrong all he could do was pull it off and send it back. i realy miss having a shop to do work for my self. blueprinting an engine is making to the dimentions that it should be. like making all the chambers the same, making the con rods/pistons weigh the same, make the deck higths the same. honeing the cylinders with a deck plate so the cyl is round as if the head was on it, sometimes they heat up the block with water so its just like it is all put to geather.
moe7404
Hardcore RCTalk User
Military Veteran
- Thread starter
- #57
well i just got the sc off my t-maxx. there was a couple things wrong. the ext pipe wasn't bolted to the engine good. the pully on the crank was rubbing driveshaft totaly messing up the grove for the belt, the throttle post was flooping around like a chevy valve train. i think its NOT going back on. iam fitting a 72 tooth gear on the trans input, may have to slot the frame again.
moe7404
Hardcore RCTalk User
Military Veteran
- Thread starter
- #58
told me so
ok ok ok you guys DID tell me so. the sc is history.
ok ok ok you guys DID tell me so. the sc is history.
Mickstix
RCTalk Champion
That was a pretty good read!! Too bad the SC didn't work out.. I'm total newbie to nitro rc, so I'm just reading a bunch of threads tryin to get a grip on whats what.. Thanks for the info!! :thumbup:
yup these guys r right the video on youtube the guy shows a motor with 3 tanks ran through after break in looked sweet good compression.. then he put a RB supercharger on it ran 3 tanks through it no compression and it ran no different and the temp was 300+F i was going to put one on my t-maxx but i wont now
