sluggish SCX needs help

Squeezing out those last few tenths

sluggish SCX needs help

Postby young again » Mon 17 Aug, 2009 12:33 am

I have an SCX Dome Judd and Ferrari 360 GTC. Both cars a sloooow compared to the Scaleys and Slot its they have to compete against. Because of rule limitations they must run the original stock motor although gearing,wheels,and tires can be changed. I have tweaked the brush hoods and could hear a positive change in RPM, but I am still in need of speed. As of now, gear ratios are 11/23 and 10/23 respectively with both cars turning 18mm wheels. I run a non-magnet board track powered by a 12 volt power pack. Majority of the straights are 8 to 16 feet in length so you can see the need for speed. The chassis perform very well with the motor pod glued tight, but I am getting my butt thumped by the Scaleys and Slot its.
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Re: sluggish SCX needs help

Postby Perro » Mon 17 Aug, 2009 9:38 am

From what I have read into your post you have 3 issues to deal with here.

Firstly you are starting out with an SCX car who's motor is at least 2000rpm lower than next best most likely being a Scalextric at 18000rpm. Most box stock Slot-it cars are fitted with motors rated at 25000rpm or there abouts so in the motor department you have no chance what so ever in matching it with those cars. Actually the Scalextric, Ninco and Fly crew have as much chance as you at level pegging it with a Slot-it runner but on shorter tracks they at least have a chance more so than SCX punters. So on motors alone you have no chance of matching the other cars.

Second problem is your gearing. 11/23 or even 10/23 is way to long. To make use of those ratios the track would need to be long with massive straights that are much longer than those you have mentioned. Shorten the gearing to at least 9/24 or preferably 9/27 so the motor can rev a little more.

Thirdly your rules suck big time. No way are they helpful in matching cars evenly. Rules need to allow for parity and enforcing a rule which states motors must remain original fit then allowing a car with lets say a standard 30000rpm motor to compete against one with 14000rpm is just nuts. To have any chance with those rules go out and buy a car with a bigger motor, it's that simple or do as most clubs do. And that is to have rules whereby cars for a individual class capture as many cars and manufacturers as possible but still allow for anyone competing to drive any one of the cars that are deemed eligible to be able to win. In our race groups we restrict the motor rpms to either 18000rpm or 20000rpm. This way it allows most manufacturers to compete because they pretty well all make cars with motors that fit that criteria. Slot-it do not. We run a separate class for Slot-it cars.

Phil has the know how to make the SCX motors run to their full potential but not many others have that skill. An SCX Pro motor or most "B" designation motors such as the RX42B rather than the RX42 are a far better option if you choose to stay with SCX cars. Strange thing is some SCX cars come standard with the "B" motors while others don't but you can easily buy a Pro-turbo from most slot suppliers to replace the standard motor. I think RX42B is rated at 18000rpm which is right in Scalextric territory.

I hope this helps you sort out your predicament.

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Re: sluggish SCX needs help

Postby wixwacing » Wed 19 Aug, 2009 11:10 pm

High YA

Glen is about right in his summing. One thing to remember though is that SCX motors draw more current than Mabuchi style 'S'cans and therefore need a better power supply to run well. 13.8v +

ie. A mabuchi will be superior on lower voltages and an SCX will start to shine towards 14 volts and more.

On any track I wouldn't go lower than 2.7 : 1 final drive and 3.0 : 1 should be fine for technical circuits. Motor tuning like retarding the brush timing and polishing the armature works but you must remember you are reducing the torque with each action so, make sure you dont go too far or you will end up with a hot (literally) motor! Always remember to tune the brush timing in the direction the motor will normally spin as it is quite possible to get them to run better backwards, which is not good.

Apart from that, all other slotcar rules apply. Essential is a quiet contrate, good tyres, braids, oiled motor and axle bearings, some essential ballast in the right spot and a guide that sits as deep as possible in the slot. Body tuning will be necessary for corners so you are first out of them, not last. The Pro Turbos and the 42/82b motors should be able to do the job against standard Nincos and Scaleys.

Let us know how you get on.
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