Post by Peter Seager-Thomas on Nov 21, 2012 16:02:36 GMT -5
A subject with no posts, aha!
Opinions please, why the opposition to high RPM slimline motors?
On a thread, on another forum, I received a few cynical comments regarding my use of 30K Sport motors in my models. I cannot help but wonder why? I have used standard (18K?), and Sport 20K, 25K and 30K, using standard sport controllers or my old MRRC Clubman (40K) controllers and I have had no problems with the 30K motors.
30K motors have been fitted to Talbot Lago, Alfetta, MG K3 and Austin Twin Cam, all being docile at low speeds, with a wide band remaining in the upper levels.
Opinions please on these high RPM slimline motors, which have an undeserved reputation.
Perhaps they just suit me, though my own preference is towards the S Can motors with the better braking.
I think, it depends of the voltage, too. If you have a windy track with short straights powered by a variable transformer, you may use the high revving motors at 8 or 9 Volt, what makes them smooth.... Kind regards, Taffy
Post by Andrew Rowland on Nov 22, 2012 15:20:22 GMT -5
High revs but no brakes, so if you have 7m long straights as are popular in Italy you have to brake half way down the straight..... Unless you really gear down which makes for huge crowns. Too big for my scale F1 models.
Post by Peter Seager-Thomas on Nov 22, 2012 17:05:05 GMT -5
Home track, short straights max 1.65m, dual supply at 12v. Standard Scalextric Sport controllers. I think Taffy answers my question.
7m long straights? I wish.....
Horses for courses I guess, I just wondered why the high RPM motors has such a poor reputation when they can be quite excellent. i have tried them with 15 ohm controllers and they just don't work on a small track.
So, if I can just shoehorn a 30k S can Scaleauto into the next K3 all should be fine, I'll have braking too.
I'm convinced that the choice of motor you use, depends on your needs, use and car type.
"Needs" here by I mean what do you want to do with the car, is it for club track racing, do you want to drive on your attic on a small track, are you in competition,or do you want to see a nice historical car run in scale. And if you take scale seriously, almost all cars pre 1950's, perhaps even a little bit earlier, didn't have the power like a modern F1, and for those who had the speed could only run it in a strait or curved steep banking's. This can be seen with John Cobb's Railton, it was so heavy that it would stick on an uneven concrete curved banking at Brooklands with a big radius. But if you would put Fernando Alonso with his Fiberglas Ferrari car body, his suspension would be gone halfway the banking and the hole thing would be catapulted of the track. Same thing would happen if you put the Railton on a modern track, it could never reach full speed without flying of the track. For those who remember the 60's when Sir Jacky Steward started to complain about track safety, race cars at Nuremberg were more flying then driving. And this principal put it self trough in slot cars, Andy with it's high tech cars is in need of such a technology, while I, with my pre war Gp's, mustn't care that much about it. Actually you can go as that far, that a circuit must be build to the era of the cars you run.
"Use" if you run a car on a small track, I don't think that it matters much, what kind of motor you use, as long that its strong enough to keep the body going in a pleasant movement, every thing will be fine, even if you go out of a corner, the kinetic energy won't be strong enough to do permanent damage to the body structure and chassis. Of course, you must put in barriers if you run it on a table, a drop from the table will also be as even distructive. But if you are going to run it on a 7m club track as Andy stated, than you car must be tuned very well, and than every part becomes very importand. The wait of of the car must be very low, because the more wait you have, the longer you need to come in full speed. And when you run up in full speed, it takes you longer to lose the build up kinetic energy. The motor must have a balanced RPM, to low it won't come up to it's full potential, to fast it will be come uncontrollable and airborne. The chassis must be able to change it's center point of gravitation, this can be achieved by springs, twisting chassis and and minimum distance between the underside of the car and track, to create an optimal down force.
"Car type"So your motor's RPM and it's breaking point will be very importand if you drive modern racers. So the RPM will depend on the kind of motor you buy, and your track currency you put on the track. So if you have a motor 12V 25000 RPM, and you run it on a maximum voltage of 9V you'll never get the 25000 RPM, but it won't get any wear, and it will last you a life time. But if you put 14V to it, it will give you probably more than 25000 RPM but it finely will have a shorter life time. And brake will only be achieved by finding a perfect balance in gearing. This will depend on the sum of the RPM and the kinetic energy of the hole car it has to brake. This makes me think of what was shown on Top Gear, where they compared braking point before a corner, with a common car and a modern F1 car. The Common car, that I compare with a pre war GP racer, had to break several hundred meters be for the corner, while the F1 car started to break almost at the beginning of a corner. Here I conclude that break power, motor speed, is really something needed for race cars post 1950's and on a purpose build track.
But some times over power also can mean fun and could be a training of your driver skills. I had that experience with driving Peter's Austin twin Cam with a 30000 RPM motor. I reacts super fast and you must be very concentrated to keep it on track . But it also gives you an inside how to behave in corners and improve you driving skills. If you run it for a while, and than change to a normal car, I had the feeling that I understood the behavior of the car on the track circumstances a lot better, and allowed me to give on a better performance. That's why I tryed to persuade Peter not to change the motor to a lower RPM, and above all, it was fun to drive it. ;D
Last Edit: Nov 23, 2012 6:50:36 GMT -5 by nuvolari
All I know, Peter, is that back in the 60s we tried to get every last rev out of whatever we used. The Hornchurch track was a tight little 4 laner that came down from the roof of Mr. Penwill's garage, but we tuned MRRC 3 and 5 poles, we ran K's Mk1s which were very quick and even Microperms. We used VIP or MRRC barrel controllers as they were all that was available. If anyone had spoken of an 18K motor we'd have laughed at him. Now they're almost the norm for larger club tracks. Odd indeed. We almost always used MRRC brass bevels in the range 2.6 up to 4-1. Barrie Wade's "Onion", a C type Auto Union in balsa wood, was a blinder with a K's Mk1 and brass bevels, SMEC brass wheels and MRRC soft diamond tyres. It was reckoned Barrie had about 36,000 revs from his K's and the braking was so good it slewed sideways at the end of every straight. Nonetheless, at Runnymede's HUGE 6 lane track I beat Barrie's Onion with my Microperm powered balsa Ferrari 158. What a proud 13 year-old I was!