40 replies to this topic

[Alan Draht]

I have tested this version of the Kemtron/ Ram motor with a Koford 12 volt regulated power supply and it does not spin as fast as the Kemtron/ Ram/ Pittman endplate motors described earlier in this thread.

 

I believe that this motor suffers from 1st and 2nd order vibration issues.

 

The "1st order vibration" is caused by the fact that both ball bearings are a bit loose in their endplate bearing holes.  It's a tiny bit, but there's enough play to feel magnetic force kind of "rattle" the armature in its bearings as it is rotated slowly by hand.  Also, at top speed the bearing housings rotate in the their endplate holes.  Not a good thing.

 

I find that it is difficult to drill/ ream bearing holes perfectly, so that the bearing fits snugly, but not too tightly, in its hole, 

 

As a result of this project experience I have learned that it is important to stop the reaming process just short of clearing the hole entirely, hand-filing the last millimeter remaining so that the bearing fits snugly. 

 

That's the standard that Gene Husting writes about achieving in his 1966 Rod & Custom magazine articles describing how to build a copy of his record-setting magnesium frame Top Fuel Eliminator dragster.

 

The solution is to cement the ball bearings in their holes with the motor completely assembled using epoxy or green Loctite threadlock (penetrates assembled parts).

 

Gene must have always drilled perfect holes because he never mentions the need to cement ball bearings into place on his motors.

[Alan Draht]

The "2nd order vibration" is probably caused by an unbalanced armature.

 

Cementing the bearings in their endplate holes and balancing the armature should eliminate vibration issues and allow the motor to reach its full potential top speed.

 

Strong springs are critical to vintage dragster motor performance, too.

 

Gene Husting wrote something to the effect that the drag racer should use "Pittman (not Ram) brushes, and the strongest brush spring that Ram makes". 

 

He goes on to say, "The Ram brush spring is good, but there are better ones".

 

True that.

 

I gathered together all the brush springs I could find from salvaged and new DC-84/ 85 motors.  Very few are strong enough to use, which is when you go looking for and trying out suitably-sized ballpoint pen springs and so on.

 

Testing these motors at 12 volts you can hear RPM's increase as the compression spring's force on the brushes increases.

 

There must be a point of diminishing returns when spring strength becomes excessive and kills RPM's, but it's hard to know when that point is reached.

 

A strong spring yielding high RPM's at 12 volts on the test stand with no load may not be strong enough to achieve maximum RPM's under load at 18 volts, 24 volts and higher. 

[Alan Draht]

In closing I wanted to say that I am confused about the Kemtron X-503 designation.

 

I learned the hard way that there are subtle differences between the various Kemtron motors I gathered together over the last decade in preparation for this project.

 

From the outside, the Kemtron motors I have collected all look alike, except for the Mustang and Bronco models. 

 

The only part of the Kemtron motors that interested me for this project was the field lamination/ magnet assembly which comes riveted together as a single unit from the factory.

 

Even the Mustang and Bronco motors appeared to use identical field lamination/ magnet assemblies.

 

Also, when I took the Kemtron motors apart and compared different models it appeared that the four hole pattern is the same, and the endplates fit the same on every field lam/ magnet unit.

 

There is a key difference, however, between the inside diameter of the cylindrical "core" space inside the motor where the armature is housed when the Mustang and the 12 volt motor's field lam/ magnet sets are aligned and joined together with 2-56 bolts inserted through the four bolt holes.

 

I don't have photo of this side-by-side comparison to show here, but the 12 volt motor's "core" is smaller in diameter by what looks like 1 - 2 mm.

 

Kemtron's Mustang/ Bronco product bulletin says these items were available as complete motors, or the customer could take an existing  X-503 motor and convert it to either a Mustang or Bronco motor by ordering special parts kits through the mail.

 

So my question is this:   Are all Kemtron motors the X-503 model with interchangeable armatures, interchangeable field lam/ magnet sets, etc., but with small differences in the "core" diameter.

 

Or, are only certain Kemtron motors the X-503 model, existing on its own, separate from Kemtron's other motors, distinguished by a larger "core", and labeled a "Mustang" or "Bronco" when the base X-503 is upgraded with Kemtron's set of parts?

[Tom Katsanis]

Nice Alan you put some work into this motor.
I did some spring testing with one of my cars on 16v & had no difference in performance going from the Ram hop up springs up to springs I had sourced that were a lot stiffer.

The standard springs I think were slower when tried them but I was also playing with gearing at the time & one of the stiff springs I tried was so tight I could just get it on & the car did not slow at all.

[don.siegel]

Alan, 

 

As far as I know they were all the X-503 model, but at some point Kemtron issued an "improved" version, also lowering the price. The only difference I know of, and it took me awhile to realize this, is that the brushes and springs were a different size, and I believe they used larger brushes on the later models. I only know this because many years ago I found a box of Kemtron X-503 component parts and gradually realized that the brushes and brush holders weren't always compatible with other Kemtron motors I had. 

 

Never thought about the inside diameter, but will try to investigate - I've got a bunch of motors in their original boxes, but not sure Kemtron changed any designations when they upgraded the motors. 

 

To be continued... 

 

Don 

[Alan Draht]

Nice Alan you put some work into this motor.
I did some spring testing with one of my cars on 16v & had no difference in performance going from the Ram hop up springs up to springs I had sourced that were a lot stiffer.

The standard springs I think were slower when tried them but I was also playing with gearing at the time & one of the stiff springs I tried was so tight I could just get it on & the car did not slow at all.

 

Hi Tom,

 

Thanks for describing your experience with springs for these high horsepower dragster motors.

 

With these motors, you know the spring is stiff enough when you can't get control of the the brush/ spring assembly between your fingers to mount it onto the brush holder posts.  

[Alan Draht]

Alan, 

 

As far as I know they were all the X-503 model, but at some point Kemtron issued an "improved" version, also lowering the price. The only difference I know of, and it took me awhile to realize this, is that the brushes and springs were a different size, and I believe they used larger brushes on the later models. I only know this because many years ago I found a box of Kemtron X-503 component parts and gradually realized that the brushes and brush holders weren't always compatible with other Kemtron motors I had. 

 

Never thought about the inside diameter, but will try to investigate - I've got a bunch of motors in their original boxes, but not sure Kemtron changed any designations when they upgraded the motors. 

 

To be continued... 

 

Don 

 

Hi Don,

 

I have a little box filled with Kemtron brush hardware/ brushes which accumulates when I'm taking motors apart to harvest their field lam/ magnet sets.

 

I have noticed differences in Kemtron brush hardware (usually not the brushes themselves or the springs) based on the armature's commutator size.

[loudspeaker]

Hi, As Howie had mentioned I built a complete magwinder using the Kemtron magnet and laminations and a Ram armature (I believe 6 volts). As I recall this was 1965. As it happens, we did not have a local drag strip, so I never got to test it before sending it off to the MINRA annual mail in drag meet. In spite of this, the car, which had a Fiat body to run in the altered class, was Top Eliminator. Doing this as a complete magwinder and eliminating the endplates really reduced the weight significantly. I still have the remnants of this car around somewhere. Sandy

[Bill from NH]

Sandy, we'd all enjoy looking at your old chassis, cars, & remnants of cars if you ever have time to photograph what you have & post them on here,

[Alan Draht]

Hi, As Howie had mentioned I built a complete magwinder using the Kemtron magnet and laminations and a Ram armature (I believe 6 volts). As I recall this was 1965. As it happens, we did not have a local drag strip, so I never got to test it before sending it off to the MINRA annual mail in drag meet. In spite of this, the car, which had a Fiat body to run in the altered class, was Top Eliminator. Doing this as a complete magwinder and eliminating the endplates really reduced the weight significantly. I still have the remnants of this car around somewhere. Sandy

 

Hi Sandy,

 

I second Bill's motion. That's great that your magwinder was able to place in the Top Eliminator category of the altered class untested by you before sending it to the track.

 

I wasn't doing any slot car drag racing myself in 1965 -1966.  I was just an observer.  Then I quit the hobby in 1966.

 

Back then I had wanted to build a magwinder based solely on what I read in the Rod & Custom magazine articles at that time, and some limited exposure to other racer's cars.

 

For example, one of the NYC area's more colorful slot car racers, Angelo, specialized in building and racing his brand of "magwinder".  I think you were part of a small group of Polk's Hobby racers who visited Angelo at his home in Brooklyn to view his 1/24 scale drag racing equipment and joy ride a stolen muscle car parked outside his apartment building.

 

Also, Bruce Clark was totally into slot car drag racing at that time and he built some formidably competitive machines.  (I can't remember if Bruce favored Pittman or Ram motors).

 

There was a slot car drag strip in a hobby shop or a track facility somewhere in the NYC metro area, I think, but I can't remember its location.  I don't remember how I got to this place or returned to my home in Manhattan afterwards.  In 1966 a drag meet was hosted by this track that put up $100 in prize money for First Place.

 

Bruce couldn't make the meet, but loaned me his car to race in his place.  Bruce was confident his car would be fastest.  Long story short, I ended up racing against you, Sandy, in the final match-up.  I hesitated at the green light and lost.

[Alan Draht]

This is slightly off topic, but I wanted to say that one of the items on my slot car bucket list is to build a copy of Sandy's "'Puzzle Pan" race car.

[Tom Katsanis]

Great stories Alan & Sandy.

Would be great to see any of the old cars or parts you still might have from back then Sandy.

I started a Facebook group for 60s slot drag cars & padlock/old open motor circuit cars just over a month back if any one is interested here is a link.
https://www.facebook...1587/?ref=share

Thanks.

[Alan Draht]

Thanks Tom.  I'll check it out.

 

BTW, do you have any experience running Kemtron's 8 volt armature (the one that Ram manufactured for Kemtron's Mustang and Bronco motors) in a drag racing motor?

 

It doesn't sound as fast as a Ram or a Pittman 6 volt armature running at 12 volts with no load.  I don't want to waste time fooling round with it if it isn't going to be competitive.

[Tom Katsanis]

Hi Alan no I have not tried a stock Bronco or Mustang motor for drags the car I put together recently is the first one I have tried.
The issue with the Bronco/Mustang motor is its to wide for most of the standard sidewinder chassis's for Kemtron motors & a sidewinder Kemtron is hard enough to squeeze under some cars as it is.

Thats why I built a car for that motor I didn't have anything one would fit in until now.

[don.siegel]

True Tom, that's why I went inline on this one... modified Kemtron frame under Oscar's Car 54, Where are You? 

Don 

 

[loudspeaker]

Hi, The track was at Steinway street in Astoria Queens. I can't remember the name but think that we just called it Steinway Street. Can't remember the drag meet that you mention. I have some of my old chassis around and will try to shoot some images. Unfortunately not the Puzzle Pan, nor the car I won with at Don's, sigh. As I mentioned the bones of the dragster are deeply buried and not easily accessible. The next generation magwinder that I built used cut down Ram laminations and a three volt Ram armature. I remember taking that magwinder, as well as Bruce's, out to California on a family trip the summer of 1966. I ran them at J&Js (the hot LA drag shop frequented by Hustings and Braverman) and they were fast. It is hard to remember, but I think both cars ran about 1:06! BTW, Bruce and I, as well as Howie, are still regularly in contact. Bruce has a HiFi store in Manhasset called Audio Breakthroughs. Sandy