Airplane Guy Has Question?
12-15-2002, 06:33 AM
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Airplane Guy Has Question?
Hi guys... gotta question for you all:
We all know that displacement usually = more HP
In R/C Drag Racing (nitro), why don't (or do they?) they use rediculously large engines, such as a .40 or .60 Heli engines??? I understand that cooling is an issue, and R/C car engines have large heat sink heads to help with heat dissipation, but that is a problem that a fan or something can easily solve.
What gives?
We all know that displacement usually = more HP
In R/C Drag Racing (nitro), why don't (or do they?) they use rediculously large engines, such as a .40 or .60 Heli engines??? I understand that cooling is an issue, and R/C car engines have large heat sink heads to help with heat dissipation, but that is a problem that a fan or something can easily solve.
What gives?
12-15-2002, 05:21 PM
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Don't quote me on this....since I have never drag raced nitros....but perhaps it's due to what is sanctioned approved? I'm taking a guess here so if anyone else reads this who does know....I'm sure my education will grow...once again. 
12-15-2002, 07:22 PM
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Airplane Guy Has Question?
It is for 2 reasons.
1. A top of the line 21 has more Hp. than a heli engine (some close to 3Hp and more.)
2. The car version 21's as opposed to the airplane or heli will turn many many more rpm's. Look at the specs on any airplane engine you will find 15,000 max and heli engines you will find around 20,000 rpm's while a good car 21 will turn 40,000 rpm's. The rpm difference will make your gearing go much higher, more top speed.
Hope this helps.
1. A top of the line 21 has more Hp. than a heli engine (some close to 3Hp and more.)
2. The car version 21's as opposed to the airplane or heli will turn many many more rpm's. Look at the specs on any airplane engine you will find 15,000 max and heli engines you will find around 20,000 rpm's while a good car 21 will turn 40,000 rpm's. The rpm difference will make your gearing go much higher, more top speed.
Hope this helps.
12-15-2002, 09:55 PM
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Just used my buddies Thunder Tiger EK4S. With A .70 Helli motor. More power that any .21 I have had. And I have had some very high end Rossi's. Now I am waiting for Thunder Tiger to release the Unlimited version with the .90 helli motor in it. When this happens I will order it. Since I do not drag race either I cannot see a real reason except for the reason CRASH had. Contrary to what 3MAXXMAN said, Lack of RPM can be made up with gearing. Look at a motor cycle. The reason that they make them spin so fast is to create higher torque and HP with small displacement engines. With this faster spinning comes lots of conditions like much more wear and tear on the components. Thus the reason for he turbocharger and the supercharger. Forcing more air in a smaller space (giving the effect of a larger displacement engine) will release more power from the internal combustion engine. Now the smaller engine can make more power at the cost of wear and tear on the parts as a whole. See it still has to turn at a faster RPM to do this. The reason that aircraft have a lower RPM range is to avoid several problems such as... vibrations, weight of gearboxes, and the problem of prop tip travel into supersonic speeds, among others. I at least know this to be true in 1/1 aircraft. I have just started (3 days ago) to do model aircraft. Now all this said the .21 motors are amazing little power plants. I want to put one into my Micro RS4. Is that over kill??????
I wonder.
I wonder.
12-15-2002, 10:56 PM
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RURC, you can't make up for gearing that is not made, unless you want to custom make gears. The other problem you have are the clutches they will not and don't last. Clutch bell temps of 300+ are not uncommon with stock gearing. There are companies that are trying to find a material that will take that kind of abuse and still last. Bigger gearing will only make the problem worse. Companies like MSJ Racing and Triple H racing make lots of parts for the lack of design work by TTR, the EK4 unlimited (90 version) will only make all the problems of the 70 worse. So if you buy one Good Luck!
Here are the specs for the TTR pro70 bx how are you going to make up for that?
MANUFACTURER'S SPECIFICATIONS
Displacement: 11.49cc (.70ci)
Bore: 0.984 in. (25mm)
Stroke: 0.921 in. (23.4mm)
Practical rpm range: 2,000 to 18,000
Power output: 2.25hp @ 16,000rpm
Weight: 20.1 oz. (570g)
Here are the specs for the TTR pro70 bx how are you going to make up for that?
MANUFACTURER'S SPECIFICATIONS
Displacement: 11.49cc (.70ci)
Bore: 0.984 in. (25mm)
Stroke: 0.921 in. (23.4mm)
Practical rpm range: 2,000 to 18,000
Power output: 2.25hp @ 16,000rpm
Weight: 20.1 oz. (570g)
12-16-2002, 02:44 PM
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Airplane Guy Has Question?
I'm indifferent on the motor size/gearing issue here... but I do have a comment in regard to manufacturer's specifications -
HP is a measurement of POWER, not torque, or turning force, but a measurement of how much work can be done in a period of time. This is just slightly deceiving, if the manufacturer's were to publish ft/lbs torque specs, you could see where the actual turning force is the greatest (at what rmp). Those Rossi .21 engines approach 3 hp because they maintain a certain crankshaft torque at an extreme high rpm (approaching 40k rpm). This means they are doing more work (thus they have more hp). A .70 heli engine, for instance, may not rev as high, but exerts a greater cranshaft torque at a lower rpm. So, one could use this power plant and afford more longevity and reliability since the engine isn't working itself to death screaming at 40k. Ever heard the old saying that you should always buy big engines???
HP is a measurement of POWER, not torque, or turning force, but a measurement of how much work can be done in a period of time. This is just slightly deceiving, if the manufacturer's were to publish ft/lbs torque specs, you could see where the actual turning force is the greatest (at what rmp). Those Rossi .21 engines approach 3 hp because they maintain a certain crankshaft torque at an extreme high rpm (approaching 40k rpm). This means they are doing more work (thus they have more hp). A .70 heli engine, for instance, may not rev as high, but exerts a greater cranshaft torque at a lower rpm. So, one could use this power plant and afford more longevity and reliability since the engine isn't working itself to death screaming at 40k. Ever heard the old saying that you should always buy big engines???
12-16-2002, 03:38 PM
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Airplane Guy Has Question?
You are correct, power is equal to the torque (ft-lb) times the rpm and divided by 4900 or something near that.
So if you need 16000 rpm to make the same power as another engine at 40000, you are making a lot more torque throughout the powerband.
However, it's still not a lot of torque, roughy .07ft-lbs at max power for the TTR .7. It could have peaked much higher than that at lower revs, but with out stats or a torque curve it is impossible to know.
With that said, I'd still rather put a .21 in any dragster I might have in mind for the simple facts of cooling and gearing. I like the idea that these engines were made to run on the ground, so they stay cooler there, and the large rpm range will mean I don't need multiple speed gearing.
What do these things run normally, 132ft in 3 seconds or so?
Wouldn't shifting loose power for a fraction of a second, and maybe cost you the race?
So if you need 16000 rpm to make the same power as another engine at 40000, you are making a lot more torque throughout the powerband.
However, it's still not a lot of torque, roughy .07ft-lbs at max power for the TTR .7. It could have peaked much higher than that at lower revs, but with out stats or a torque curve it is impossible to know.
With that said, I'd still rather put a .21 in any dragster I might have in mind for the simple facts of cooling and gearing. I like the idea that these engines were made to run on the ground, so they stay cooler there, and the large rpm range will mean I don't need multiple speed gearing.
What do these things run normally, 132ft in 3 seconds or so?
Wouldn't shifting loose power for a fraction of a second, and maybe cost you the race?
12-16-2002, 03:44 PM
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Very good and valueable points from both 3MAXXMAN and LUCKYSTRYKE1
3MAXXMAN I understand what you are saying, however cogging gears sets is not hard at all. Also I am not talking about using a single speed transmission. Now the point that you say for the clutch is extremely valid. These little systems do exactly what you say. I have burned up many clutch and bell housings running off road and trucks.I am sure that the problem only gets worse with drag racing (having never done it my self). The guys (2 of them) I know who own the EK4S's to the best of my knowledge have not had any more problems than the ones I have had with nitro cars. I am unaware of serious problems in the " lack of design" areas you speak of. Not being sarcastic but please inform me as to some of the problems so I can see what can be done and if I even want this beast. I am more concerned with torque than the hp range anyhow. Torque will get you to the necessary speed faster. Now LUCKYSTRYKE1 has a real idea of the power situation. Personally hp ratings are, for the most part, BS (Barbara Streisand). When working with these measurements I like to convert them to "draw-bar HP". This dose exactly what LUCKY was talking about. Specific weight a specific distance. The wear and tear on high revving equipment is not avoidable.
For a last thought I have a question.
Is there a set standard as to horse power measurement? I mean how the number is attained? What are the specific conditions for the test? Or is it like wattage for audio amps, NO set requirements for claiming what ever? For example my 50 watt RMS Threshold amp is like a small refrigerator. It is around 18"wx14"hx22"d and weighs about 200 pounds. Now I just put a JVC receiver with amp in my hobby room. It claims 150 watts per channel rms x 5 channels. Now this all in one unit weighs maybe 12 pounds. I really think that there is a major discrepancy here. The JVC will barely run my main speakers that I run with the Threshold. The Threshold will make them bounce across the floor.
3MAXXMAN I understand what you are saying, however cogging gears sets is not hard at all. Also I am not talking about using a single speed transmission. Now the point that you say for the clutch is extremely valid. These little systems do exactly what you say. I have burned up many clutch and bell housings running off road and trucks.I am sure that the problem only gets worse with drag racing (having never done it my self). The guys (2 of them) I know who own the EK4S's to the best of my knowledge have not had any more problems than the ones I have had with nitro cars. I am unaware of serious problems in the " lack of design" areas you speak of. Not being sarcastic but please inform me as to some of the problems so I can see what can be done and if I even want this beast. I am more concerned with torque than the hp range anyhow. Torque will get you to the necessary speed faster. Now LUCKYSTRYKE1 has a real idea of the power situation. Personally hp ratings are, for the most part, BS (Barbara Streisand). When working with these measurements I like to convert them to "draw-bar HP". This dose exactly what LUCKY was talking about. Specific weight a specific distance. The wear and tear on high revving equipment is not avoidable.
For a last thought I have a question.
Is there a set standard as to horse power measurement? I mean how the number is attained? What are the specific conditions for the test? Or is it like wattage for audio amps, NO set requirements for claiming what ever? For example my 50 watt RMS Threshold amp is like a small refrigerator. It is around 18"wx14"hx22"d and weighs about 200 pounds. Now I just put a JVC receiver with amp in my hobby room. It claims 150 watts per channel rms x 5 channels. Now this all in one unit weighs maybe 12 pounds. I really think that there is a major discrepancy here. The JVC will barely run my main speakers that I run with the Threshold. The Threshold will make them bounce across the floor.
12-16-2002, 11:20 PM
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HORSEPOWERS vs HORSEPOWERS
Hi there RURC. You wondered is there a set standard to horsepower measurement?
It is. Several. Ho hum.
The two most used standards (well at least one of them is...) is DIN (Deutsche Industri Normen, Gemany ) and SAE (Society of Automotive Engineers, USA). They are very different. And then there's the British variant BHP. No, not British HorsePower, it's Brake HorsePower. Very close (almost identical) to DIN.
In your amplifier-world, Threshold would be DIN-rated, and that JVC expressed with SAE. Just to paint the picture for you.
I'm not going to thoroughly elaborate HOW they measure HP, cause everyone would fall asleep before finishing, but I'll tell you a little story about the differences.
Different ways of measuring will give different readouts on the same engine. In the late sixties/early seventies, American Muscle Cars were battling eachother with engines bursting with horsepowers. Those were SAE-gross-horsepowers.
A friend of mine has a Chevrolet with a 400 cid small-block. According to him that's 6,6 litres, and it pumps out 180 Hp (DIN). The year prior to his model, it had a little higher compression ratio, and 330 Hp. WOW !! ...err...SAE gross horsepowers.
It is. Several. Ho hum.
The two most used standards (well at least one of them is...) is DIN (Deutsche Industri Normen, Gemany ) and SAE (Society of Automotive Engineers, USA). They are very different. And then there's the British variant BHP. No, not British HorsePower, it's Brake HorsePower. Very close (almost identical) to DIN.
In your amplifier-world, Threshold would be DIN-rated, and that JVC expressed with SAE. Just to paint the picture for you.
I'm not going to thoroughly elaborate HOW they measure HP, cause everyone would fall asleep before finishing, but I'll tell you a little story about the differences.
Different ways of measuring will give different readouts on the same engine. In the late sixties/early seventies, American Muscle Cars were battling eachother with engines bursting with horsepowers. Those were SAE-gross-horsepowers.
A friend of mine has a Chevrolet with a 400 cid small-block. According to him that's 6,6 litres, and it pumps out 180 Hp (DIN). The year prior to his model, it had a little higher compression ratio, and 330 Hp. WOW !! ...err...SAE gross horsepowers.
