TOPIC:

Edit : (Arghh, this was suppose to go in "Technical" - sorry )

So, I've been wondering :

Why was there a need for four AA batteries to power the reciever/servos in the old days?

It would be very easy and cheap to knock the 7.2V down to 6V with a zenerdiode and a pass transistor (10 cent parts) .. I allways thought those batteries where cumbersome on my old (now long gone sadly) Frog ..

Secondly :

MECs have very coarse steps, but one option was to buy the 5054 "variable resistor speed control switch", which was just a large wirewound resistor giving (near) infinite steps allthough still with high loses at low speed

Was it any good? Anyone have one? If so, what is the end-to-end resistance? I have the parts to build one and might try it out on my not yet bought restoration project

Many thanx in advance

Cheers,

Ole

I moved your thread, it's a regular thing as the "introduce" category is the default


In the earliest days motor was powered by four C size cells, they wouldn't provide much power or last very long, zinc carbon especially. Nicad packs had a capacity of 1000, 1100, 1200 or mah, maybe even 1300, these would last 5, maybe 10 minutes depending on the car. The problem is, battery voltage could quickly drop to a point where it would drive the car forward (sometimes quite fast) but not enough to operate the radio gear - result being an out of control car.

Diodes, resistors (or later "BEC" technology) were a popular mod for racing BITD, if you knew a race was going to be 4 minutes and your battery would last 5 (or 8 vs 9, etc) then no problem, and the weight saving was worth it. Some cars (like the Super Champ) had a "racing speed control" which included a diode.

IMO there's no good reason to use an MSC in a runner any more.


edit - zinc oxide

Jonny is dead on, but forgot the clarify that BEC is "Battery Eliminator Circuitry (electronic device to eliminate the use of separate receiver battery)"

The MSC is probably this one: ?


It came with the early Tamiya models (more info HERE )

I'll see if there's any resistance printed on any of mine.

And, like Jonny, I would not recommend running a model with the old MSC. It's possible to do, and will probably not do any harm, but the modern ESC's are fare more efficient and more easy to regulate.

Thanks for the move, Jonny

Yes, I thought that the voltage drop from the main battery might be the culprit, but I didn't know it would drop so low that the reciever couldn't work. but of course the reason is, as you say, the very low capacity of the main battery. Now 5000mAh is common, back then I think I had tow 1300mAh and a veeery slow charger. All that auxillery gear cost more than the car

I've thought about using a MSC in a project (I'd really like to get my hands on a BigWig) you know, just to keep it real. The variable one must surely be better, no?

I know they suck compared to ESCs

Thanks for the info

Cheers,

Ole

larbut wrote:

Jonny is dead on, but forgot the clarify that BEC is "Battery Eliminator Circuitry (electronic device to eliminate the use of separate receiver battery)"

The MSC is probably this one: ?

It came with the early Tamiya models (more info HERE )

I'll see if there's any resistance printed on any of mine.

And, like Jonny, I would not recommend running a model with the old MSC. It's possible to do, and will probably not do any harm, but the modern ESC's are fare more efficient and more easy to regulate.

Yes, that's the sucker, thanx for the links. I'd love the ohm info

Don't worry, I won't be using it for serious running cars, I just would like to build/restore it as good as possible in 198X (<-- which is still academic as I don't actually have that car, sigh)

I like the oldschool stuff even if it's hopeless by todays standards

I guess I'm sort of an RC Archaeologist



Cheers,

Ole

I remember the variable one, like the one I linked to, had problems with the wires burning off with too much load.
They were designed in the 6V period, and usually for small, light models runnung maximum a standard 540 motor.

I measured the resistance in the coils of one of mine, and it looks like there about 1,2 ohm from the centre to the end. (that is if I understood what I was doing with that multimeter...)

Thanks for the measurement

Measuring below 5R with a standard multimeter is difficult though, the wires are probably several hundred milli-ohms, a four-wire device is needed

But it will give me a point to start, I can wind my own resistor to make sure it doesn't end up in smoke

Did any of the Tamiya cars from that period come with it as standard? I'm still looking through my newly aquired catalogues (I'm surprised to see a ESC allready in 1990 in the BigWig)

Cheers,

Ole

Holiday Buggy & Sand Rover have that type of MSC as standard, other cars too but TBH I can't quote them of the top my head & can't really think of a definitive list of MSCs either - I guess someone would need to look at all the early cars.

1.2 ohms sounds in the right ballpark, I don't have cars to hand to look at but I know the Wild Willy & Wheeler have two 5W, 0.3 ohm cement packages wired to the 3- step MSC (combined on the lowest speed setting) & I'm pretty sure the early Frog had two 0.7 ohm units, I remember because I tried to get some replacements & couldn't, and had to use 0.5 and 1.5 ohm packages, which made for some interesting speeds (_really_ slow, bit too fast & flat out) but they looked the part.

ESCs, I remember someone hearing that someone had an RC10 with one in the mid 80's, but it was an upgrade that niether me or any of my friends could consider, 1990 I don't think would have been that different in the real world either

Very good info Enough for me to make my own

Many thanks!

Cheers,

Ole

HI!... The Bigwig came out in 1986 not 1990. It had a MSC, not a ESC. I should know. I have 9 Bigwigs.