22 replies to this topic

[Gary Bluestone]

I recently got a Dynamic chassis with a motor already mounted, as can be seen in the following photos. There was an opened card by Dynamic No 508 for Tradeship Mk70. I was guessing that this belonged to the chassis but that could be wrong.

So here is my problem, the motor (armature) shaft on this motor is so long, it would prevent the axle and crown gear from being installed. Is this the Tradeship Mk70? This one has adjustable timing! Is this the Dynamic 508 chassis? Was it common practice to shorten the motor shaft?

Gb

[Jairus]

Yeah, I am afraid it was. Those motors were originally designed for model trains so the shaft length could vary depending on the application.

I would slide the gear down to where you want it and cut the shaft!

[Gary Bluestone]

Yes, I was afraid of that. Don't like to modify vintage stuff unless totally necessary.

I also read that the Mk70 was used for model boats; you could probably put a prop on that thing.

Gb

[Gary Bluestone]

Is this the Tradeship Mk70? This one has adjustable timing!

[Pitt Man]

Hi Gary,

Yup, that IS a Tradeship MK-70 and that IS the correct Dynamic chassis for it.

Here are a couple of MK-70's out of my motor collection, a 12 volt and a 6 volt version.

As you can see, they both have adjustable timing.

Back when I was a youngster in 1965, I built a 1/32 scale car with the MK-70 and a Dynamic frame. The car was very narrow and with the torque monster MK-70, it would break contact with the track braid when you punched it.

Not a wheelie mind you, but it would actually pick the left side of the car up, break contact and continue the cycle! Zzzt, zzzt, zzzt!

What a sight ot see.

Have fun with yours!

[don.siegel]

Great story Pittman! I've never seen, or maybe noticed, the 6V version of this motor before - are the specs any different?

Don

[Gary Bluestone]

Thanks Guys, I knew I could count on you ! I guess I'll fire up the dremel and cut down the shaft. If this motor has that much torque, maybe I'll start with the stock pinion (10) to a 24T crown , and go up if need be, leaving the shaft long enough for that setup. There isn't much drag when turning the shaft by hand so I guess the magnet may need a zap , or is there not much drag with these 7 pole arms? Gb

[boxerdog]

There isn't much drag, because of the 7 poles and the skewed field pieces, but I'd zap the hell out of it amyway! Maybe weekly! I remember a few guys running them, cranking up the timing, etc. If I recall, they would go but not stop....

Thanks Guys, I knew I could count on you ! I guess I'll fire up the dremel and cut down the shaft. If this motor has that much torque, maybe I'll start with the stock pinion (10) to a 24T crown , and go up if need be, leaving the shaft long enough for that setup. There isn't much drag when turning the shaft by hand so I guess the magnet may need a zap , or is there not much drag with these 7 pole arms? Gb

[Steve Deiters]

I've never seen these motors before. I noticed in the endbell area that there are grooved slots that look like they could be loosened to rotate the endbell and advance or retard the timing. Is that the case or were they there to just hold the motor together and the slots made for easier assembly?

[don.siegel]

Yes, this motor has adjustable timing Steve. I remember these from the magazines, but don't actually remember seeing any in the hobby shops or raceways where I hung out! Got a bunch now, for various projects, not only the MK-70, but also the MX77??, and one or two others...

In one ebay lot, I even found somebody's idea of the ultimate land speed car: a flat pan folded aluminum chassis for four of these Tradeship motors! Shades of Mickey Thomson...



Don

[Pitt Man]

Don, as far as specs go....

The only specs I have are on the 6 volt motor's box and as you can see, they used a red marker to cover up the 12V! The front of the box had the 12 scratched off and restamped 6 also. There is a very noticeable difference in wire gauge of course.

The 6V has a brighter copper wire over the 12V model and I also see the 6V has a white felt oiler over the drive end bushing opposed to the 12V's green felt.

I find it interesting how tiny the brushes are in these large motors.

Here's a shot of a NOS package of brushes and springs. Notice they come with shunt wires attached to the brass arms. The "huge" brush I laid on the package, for size comparison, is a stock Parma 16D brush!



Holy cow, Don, your eBay LSR car has given me the giggles.
It no doubt stuck terror in many a youngsters' mind back in its day!

[Prof. Fate]

Hi

Don, they are common because they weren't competitive and, thus, didn't get raced to destruction! I think I have a couple NOS that I inherited with someone going out of business and having the maul the stash away.

Fate

[Pitt Man]

Hi guys,

 

Beings how this is the only MK70 thread I can find, I thought I'd add a couple more pics for future reference.

 

I recently acquired another 12volt MK70, this one with green wire! First one I've ever seen.

 

 

Another goodie I picked up is a 6 volt armature for the MK70.

 

Gary, did you ever finish your Dynamic project?

 

 

[don.siegel]

Thanks Pitt, 

 

I had completely forgot about this thread, and am fascinated to see how many variants there were of a relatively unpopular motor! 

 

I'll have to keep an eye out for some more of these... anybody know if Dynamic made a chassis for the Tradeship MK77 too? That's another big one, but flatter than this, with cylindrical brushes and no variable timing .. (if I remember right, the specs were also 20k rpm...)

 

Don 

[Gator Bob]

Some pictures for documenting the Micro-Motor series. If anyone needs a different angle please let me know.

 

One 12v green wire and one 6v heavier wire.

Magnets are soldered in.

6.25/B price showing.

 

 

 

 

 

 

 

 

 

 

[Gary Bluestone]

Hi guys,

 

Beings how this is the only MK70 thread I can find, I thought I'd add a couple more pics for future reference.

 

I recently acquired another 12volt MK70, this one with green wire! First one I've ever seen.

 

 

Another goodie I picked up is a 6 volt armature for the MK70.

 

Gary, did you ever finish your Dynamic project?

 

 

 So far, I cut the shaft, pressed on a gear , fitted a tapered axle with Cox wheels and tires and added brushes and wired the guide. I don't think I ever took it for a test run since the tires look ancient. I didn't expect too much performance from this chassis so I decided to use it under the re-issue Munster Coach. I have filed away at the front axle mount so it fits the body and cut a notch for the 36T Wilson gear into the rear of the body. One of our local racers is making some repro urethane Cox tires, so when I get some of these,  I will at least test run the project.

[Gator Bob]

Same motor/chassis set-up can be found here:

http://slotblog.net/...-chassis-combo/

[Pitt Man]

Hi guys,

 

I've recently learned a bit more about the MK70 as I'm building one for a drag car.

 

 

I found that the felt oil wick's color does not distinguish 6 or 12 volts as I earlier thought. I now have 12 volt versions in both colors.

 

The 12V version is wound with #31 wire and the 6V sports #28, turns are unknown.

 

Tiny little .193" comm with it's itsy bitsy 7 segments looks out of place on the huge .790" arm.

 

What was Tradeship thinking, the armature shaft diameter is .098", 4-5 thou too big for 3/32" pinions! I've rounded up a #40 (.098) reamer for future use on pinions.

 

Here's a shot of the motor back together and a shot on the Hudy. Epoxied and balanced nos 6V arm in a 12V motor, trued comm, endplay adjusted. It will receive a much needed magnet zap later this week.

 

 

 

 

 

[Gator Bob]

Pitt,

I haven't taken mine apart...

when you had it apart did you see if it is set-up that the can rotor slot center is zero timing advance or zero is at one end of the slot and it has 'That' many deg. of advance available to crank in.

[don.siegel]

Thanks for added pix - very odd indeed those two details you mention. 

 

Don 

[Pitt Man]

Pitt,

I haven't taken mine apart...

when you had it apart did you see if it is set-up that the can rotor slot center is zero timing advance or zero is at one end of the slot and it has 'That' many deg. of advance available to crank in.

To my eye, Bob, it appears to be all in one direction from 0 timing. Set for clockwise on the drive end.

 

The arm itself looks to be at 0 also.

 

My Mk has a hot date Friday with a Carlisle zapper. Right now with the magnet's weakened state, this motor revs up SCARY high even at 0 timing. I need to trade back some r's for torque.

[Gator Bob]

THanks Bob,

 

Then ...... there is a lot of 'room to advance' using an MK-70.

 

Hope to see it 'on the strip'.....

[SlotStox#53]

Cool pics and info definitely an odd combination! Sounds like a potential strip monster