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For Sale: tjsguns 'Dynapower Brake Box'


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#1 tjsguns

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Posted 02 November 2017 - 11:13 PM

I have no idea what this is or what it's for. Can anyone tell me?
 
Best offer by 11 PM Eastern time, November 18, 2017. Note that this item is being sold “AS-IS.”
 
You can post your offer in this thread, or if you wish to remain anonymous, send your offer (stating clearly which car) either in a PM to Cheater here at Slotblog or email him at greg@slotblog.net, and he will post it for you without identification.
 
Please note this NEW REQUIREMENT: So anonymous bids can be posted to the threads before the auction ends, anonymous bids must be sent ONE HALF HOUR before the ending time listed for the car. For example, if the bidding closes at 11 PM Eastern for posted bids, anonymous bids must be received by 10:30 PM Eastern, whether sent via email or PM.
 
Buyer to pay shipping costs. Shipping in most cases will be via USPS “First-Class Package Service,” at least within the US. International shipping will be by method of winning bidder's choice at his expense. A small amount will be added for the cost of packaging materials. If insurance is desired (above any amount automatically included) the additional cost will be at the buyer’s expense. It is not expensive to add insurance to First-Class Package Service (for example, $200 of insurance costs just an additional $3.35).
 
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Thomas J Scott
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#2 Cheater

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Posted 02 November 2017 - 11:24 PM

I'm pretty sure this is an add-on external brake box that increases braking by using batteries to supplement the braking effect provided by so-called "dynamic braking."

 

Dynamic braking uses the fact that PM DC motors act as both motors and generators at the same time. When a PM DC motor is being powered and thus is spinning, it also generates a voltage of opposite polarity to the voltage being applied to turn the motor. This is called 'back EMF' and the top speed of a PM DC motor occurs when the level of back EMF equals the voltage being applied to make it turn.

 

In dynamic braking, when the controller reaches the brake band, it connects or 'shorts' the motor's leadwires together and the still spinning motor then 'sees' the back EMF which means the back EMF will try to make the now-unpowered motor rotate backwards. This is what provides the dynamic braking effect.

 

The box Tom is selling has two "C" cell batteries in it and their voltage is added to whatever level of back EMF the motor is generating to increase the braking effect.

This has to be a very early device, as external batteries have been prohibited in controllers and the like for quite a long time. Rare piece of kit, this, and certainly a collector's item.


Gregory Wells

Never forget that first place goes to the racer with the MOST laps, not the racer with the FASTEST lap


#3 tjsguns

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Posted 04 November 2017 - 02:12 AM

This thing is NOS and has rarely even been taken out of the box (which is in excellent condition as well) so no batteries have ever been in it and no rust or corrosion either.


Thomas J Scott
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#4 Cheater

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Posted 19 November 2017 - 12:01 AM

No bids were received on this item, so no winnng bidder.


Gregory Wells

Never forget that first place goes to the racer with the MOST laps, not the racer with the FASTEST lap






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