# HP, Speed, and Clutches

Discussion in 'RC Onroad Forum' started by dudex, Jan 29, 2004.

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1. ### dudexMember

First I would like to say that I am not rockn82. I am 18 senior in Maryland and work in a hobby shop. Second I have worked in the hobby shop since I was 15 and have been doing nitro for the last 2 and half, so at this point I have quite a bit of experience and have also talked to a lot of other people who have experience. In this thread I would just like to point out how full of shiat tim is.

So Tim, read this whole thing before you say some b.s. about how you don’t feel like reading my lies because it is too long. I tried explaining things to you before, but now I will go in depth so that there will be no misunderstandings.

This thread is not just to bash Tim but to explain about some common misconceptions and fuzzy areas of nitro cars, (although I definitely plan on embarrassing him).

I strongly encourage everyone to respond to what I have to say and if you think I am wrong on something I would appreciate it if you would post what you think is wrong and exactly why you think it is wrong instead of just saying “oh youre an idiot you don’t know what youre talking about”. I have no problem with constructive crticism. Also I would appreciate it if no one would post without reading everything or with only reading a part of a section.

HP
Horsepower is the ability to do work over a period of time. The basic equation for determining HP from torque and rpm is HP=(Torque X rpm)/5252. Tim thinks it is
HP=torque +rpm. If his equation were true then when the average .12 sized engine puts out 1hp at 30,000 rpm, then according to his equation 1HP=torque + 30,000. If we rearrange this equation then we get Torque =Hp-rpm and substituting the numbers in we get Torque=1Hp –30,000rpm. So then according to his equation this average .12 engine has negative 29,999 ft. lb’s of torque.

Why HP does not have anything to do with top speed(do you like my wording Tim?)
Horsepower can be used to calculate maximum speed of your car, but not the top speed. Maximum speed is how fast your engine has the ability to move your car.
Top speed is how fast your car will go with the gear ratio and tire size that you have.
Eventually, no matter what your gearing, you will not be able to go faster because of frictional forces and the torque required to turn the wheels. If you had a runway long enough then you could probably get your car to go a couple hundred miles an hour, it would just accelerate slower than a snail. Now top speed is how fast your car will go with the setup you are using. The max HP of an engine will let you calculate the maximum speed of your car but not the actual top speed based on your setup. Actual speed is determined by knowing the final drive ratio of your car, tire circumference, and the max rpm of your motor under the load you are using. Max rpm is not the same as max HP. Max HP in a nitro engine is usually found around ¾ of the max rpm depending on the power band of the motor.

Clutches
I have already explained this one so will just copy and paste.
The point in engaging later is that first you have more torque at the higher rpms. Second, if you have two identical cars with the same motor, both idling at 3,000 rpms, and one of them engages at 7,000 and the other at 3,500, the one that engages at 7,000 will accelerate quicker. The time it takes for it to spool that extra 3,500 rpm under no load is probably about .07 seconds. The time it takes for the other motor to spool up to 7,000 rpm while trying to move the car is probably about.4 seconds. Now in that .07 seconds time for the first motor to spool to 7,000 and then engage the second car has probably gone about 1-2 feet, ad is now turning maybe 4,500 rpm. WHen the first car takes off with the motor spinning 7,000 while the other car is only spinning 4,500 that extra 1-2 feet that the second car has gone will be quickly eaten up by car one as it is turning 2,500 rpm faster than the second car.
2. ### rockn82Marx Brother

Hey DUDEX, I already tried to explain this and of course he wouldnt read it simply because, well I am not sure. Makes me wonder if he even can read...
3. ### danny_holtermannMember

Hey cluchess don't engage at a seperat time unless you use a certain spring. but centifugal forces you can loosen and tighten, if I am wrong correct me don't hat me like you do w/ tim rock, k
4. ### timrockActive Member

ok, rockn83/dudex ,eveyone knows you are the same dude.also,the point about HP was the fact that rockn82 said HP has Nothing to do with the top speed of a car.

then he looked up on the internet and found this formula and acted like he knew it the whole time and that it is his formula.thats how people see him as a retard(meaning slow/to late.)
5. ### dudexMember

It doesnt have to do with top speed of your car. It has to do with the maximum speed your your engine can make your car go. not the actual top speed.
6. ### timrockActive Member

wrong.it does have to do with the top speed of the car or any speed.

it makes me laugh to hear these guys say hp has nothing to do with the speed of a car.
7. ### timrockActive Member

actualy it is one guy.rockn82=dudex
8. ### mastmecMember

For God sake people, horsepower is a statement, not a factor!!!!!!

lmao
10. ### timrockActive Member

it can be a factor in estimating speed.
11. ### mastmecMember

Torque and rpm are what you figure in to est. speed.
12. ### mastmecMember

And what are you laughing at? What do you do for a living, and how long have you been dealing with cars of any type, R/C or real, how long have you been engineering cars? Because you argue with everything, and never stay with one cause or effect.
13. ### timrockActive Member

no.i dont.i use a speedometer and/or a radar gun.but im sure it can be used to estimate speed.yes.

some people use the power to wieght ratio to estimate speed.
14. ### timrockActive Member

i was laughing at your yelling at us `for god sake people........!!!!`lol
15. ### mastmecMember

Power to weight ratio has nothing to do with speed. Run a car with a .12 then run it again with a .21 without changing the gear ratio, and the .12 will smoke the .21 any day, and the .21 has more power, like twice as much. Explain that.
16. ### timrockActive Member

to say power to wieght ratio has nothing to do with the speed of a car,i would have to disagree.like i said som people use the power to wieght ratio and some how estimate speed.i use a speedometor and/or radar gun.
17. ### mastmecMember

Explain how, if you disagree.
18. ### timrockActive Member

they use the power to wieght ratio as a factor.
19. ### timrockActive Member

so if they use the power to wieght to wieght ratio as a factor in estimating speed,then i would disagree with you about saying it has nothing to do with speed.
20. ### mastmecMember

I said explain, not repeat yourself. How would that ratio fit in to factor speed? Go ahead and get as technical as you want. Lets make this an intelligent arguement.