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Thunderjet 500 and Compatible Pancake Motor Armatures


Sweet, even without syrup...

The pancake armature motor was used almost exclusively by slot car manufacturer Aurora in their HO scale and "O" gauge slot cars. They could also be found in some Faller HO scale slot cars as well.

Below is the FRHO Guide to Aurora Pancake Armatures. It is intended simply as a "spotters guide" and can give you guidance when sorting through your pit-box. Use the description of each armature to help you find the best Aurora armature for your Thunderjet 500 slot car racers.

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Early Thunder-jet 500

  • OHM Range: 17.5 - 21+
  • Copper, Red and Green Wire with Gray Tips

Ahh... The "Christmas Tree" armature - the Model T of pancake slot car arms...
These were usually found in the earliest Thunder-jets, the type with the solid rivet, or "button" chassis'.

They typically OHM pretty high, fairly uneven and tend to run hot when used with stronger magnets. If you have some of these, you may be better off putting them in your older keepers along with a solid rivet chassis and set of matched black magnets to retain their originality and value.

However, if you can find that rare one with equal resistance winds, a good pair of weaker matched magnets can make for a fairly responsive racer.

There were some variations of this arm; You may find some with (Green|Red|Green) colored poles or even (Red|Green|Red).

Typically, Arms with 2 similar colored poles seem to have steel instead of copper center shafts; they also seem to have fairly decent ohm tolerances as compared to their tri-colored brothers.

Performance part? Rarely, but they could be readily be found the early days of the Fray...

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Later Thunder-jet 500

  • OHM Range: 15.0 - 21+
  • Copper, Green or Red Wire with Gray Tips

This is a Slot Car Racing Armature?
You bet. At first blush, you probably wouldn't choose one of these for a racer (due to higher OHM ratings) however these are actually pretty good arms and just happen to be the type of arms found in T-jet fray-style club racing.

If you take extra care when hand-picking one of these, it usually pays off later on the track. When picking one for fray-style racing, try keep pole-to-pole ohm tolerances to +/- .1 and use matched magnets for best performance.

There is an article on the VHORS site reviewing Magnets; it suggests that stronger Super II and JL Magnets didn't provide any better performance than medium strength Matched Magnets.

Current fray rules allow for Johnny Lightning Magnets, due to the strength matching being very consistent.   You might be surprised at what one of these will do! These will still yield better Seat of the Pants results in a T-jet than a lower ohm magna-traction arm in most cases.

Here's a rare & unusual single lam version of this generation armature. Photo by Dennis Sieck

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Wild Ones and early A|FX (except magna-traction)

  • OHM Range: 5.0 - 8.0
  • Green Wire with Gray Tips

What Gives?
At first glance these arms seem to have the characteristics of potential, but for some reason fall short. We've never taken the time to pull one apart, but it can only be due the wire thickness, amount of winds or combination of both.

They seem to run hot and don't respond as readily to stronger magnets. Easily confused with higher resistance early T-jet Arms due to the color combination.

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Speed Wind (Wild Ones)

  • OHM Range: 6.9 - 8.0
  • Green or Green Wire with Green Tips

As the predecessor to the Mean Green, this arm was intended to be used with the 12t pinion contained in the original Aurora Hop Up kit and could be found in some of the Wild Ones cars.

Also available as a separate item for a limited time through Auto World. Like its "Tuff Ones" big brother, It demonstrates good top speed with just a slightly lower torque Profile. Best suited for cars that have been lightened, or use some of the lighter bodies & wheels.

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Tuff Ones

  • OHM Range: 6.0 - 7.5
  • Green or Copper Wire with Green Tips

Available on the Aurora Thunder-jet Tuff Ones series of cars, these were the fastest armatures produced by Aurora for the Thunder-jet style chassis.

Tuff Ones were produced after the Wild Ones and offered increased performance (advertised at 760 scale MPH!) and a few new body styles. The Tuff Ones also introduced the 14t Cluster Pinion which is probably why these arms produce a fairly good mix of top speed and low-end torque. When run on 20V with the proper amperage, these can really come alive... Tuff Oone arms were also available on some of the earliest AFX cars as Aurora transitioned from 'screw-on' T-jet to 'snap-on' A|FX bodies & chassis's.   The early Tuff Ones arms had Copper colored wire with later models having Green wire. Unfortunately Aurora decided to re-introduce the Copper & Red color combination on most of the AFX magna-traction cars throughout their production runs.

Use the ohm meter as your guide, because you don't want to confuse the earlier Copper|Red Tuff Ones arms with the later Copper|Red magna-traction arms if performance is your goal.

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