14 replies to this topic

[Big Booty]

How do people go about setting the spring tension on their motors? Is it a case of "suck it and see" or do people use some sort of "scientific process"?

I once read an article that said too low a spring tension and the brushes don't scrape away enough of the copper oxide that is formed by the arcing process. Too high a spring tension and you scrape away too much of the oxide layer. Just right and the amount of oxide formed is the same as the amount that is scraped away. Since copper oxide has a lot lower coefficient of friction the article said that a very thin layer (nanometers) was a good thing.
 
So how do people set their spring tension?
 
 

[Bill from NH]

I use a "Thorp Fiddlestick", the original to the Sonic versions, to set both springs at the same tension

[Big Booty]

Do you have a link to a site that sells Fiddlesticks? What does it look like?

I'm assuming you get the tension the same with the Fiddlestick but how much tension do you run in the first place? Given that the positive and negative brushes behave very differently with respect to electron flow I'm not convinced that you need the same tension on both.  

Hence I'm wanting to play around with the tensions, so a Fiddlestick would be good.

[Guy Spaulding]

You're most likely to find a Fiddlestick on eBay. Some use a Xipp spring dyno, but that's 50 bucks. Yet others rely on the consistancy of brand new Champion red springs right out of the bag. But now that Parma makes Champion, I dunno if that works any more.
 
In brush-type Stock Class R/C motors, the "pros" insisted on specific tension and specific brush hardness on the positive and negative sides.
 
But, I haven't found many who agree on spring tension in slot car motors. Most agree that equal tension is desired, but accuracy is not paramount. Too little is bad and too much is bad. But somewhere within a range works equally as well. Low tension for low current motors, higher tension for higher current motors. I run 3 fiddles for a Deathstar, and used to run 4.5 Fiddles for G7 motors.
 
Here's three iterations of the Fiddlestick:
 

[Bill from NH]

Rick,

My Fiddlestick is nearly 45 years old. If Sonic, on the other side of the country, no longer makes these, eBay might be your best choice for getting one. If any shop still has new ones hanging on the wall, it'll be someplace like (PCH) in California. You could contact them:  (805) 988-8044, (800) 258-7441 to see if they have any.
 
Guy, if one wanted to get anal with those Fiddle numbers, since Fiddlesticks' internal spring tensions vary, you can calibrate them using a gram scale. I've never had the need to do this.

[Samiam]

I saw an evilBay auction for an older brass Fiddlestick go to over $70. Not sure what was going on there but I do see them by themselves and in lots. I will never sell my old one.
 
But I have a newer one floating around somewhere. Hope I find it before I die. Otherwise it will be thrown in the dumpster with all my other "toy car junk".

[Guy Spaulding]

Guy, if one wanted to get anal with those fiddle numbers, since fiddlesticks' internal spring tensions vary, you can calibrate them using a gram scale. I've never had the need to do this.  

 
Surprisingly, these three Fiddlesticks measure within 1/10 fiddle of one another.
 

I saw an evilBay auction for an older brass Fidllestick go to over $70.

 
I saw that one, too. Think it was the silver barrel with brass ends like the one in the middle of the photo. I also saw one for $47. But others go for under $20, and HERE's one now. This auction failed to sell at $16. I suspect the reserve may be $20.

[gotboostedvr6]

I have a brand new Fiddlestick I'd sell.

Never been done fiddled with it.

[Samiam]

[Big Booty]

Thanks, guys. Too helpful on this site... Err, even the YouTube clip.
 
A question. For the guys that have set up their spring tension equally, have you noticed which brush wears more? I'm thinking the positive brush will? Can I get some feedback on this and I might have to take a consensus if the answers vary.

[gotboostedvr6]

Pos brush wears more. No poll needed.

[Big Booty]

Thanks, that confirms my thinking that it would be the positive brush that would wear more as electrons are jumping off the comm and smashing into the face of the positive brush.  

Not sure whether that means I should try more or less spring tension on the positive side??

[Bill from NH]

I've heard, but have no experience, that some racers use a Goldust brush on one side and the harder Big Foot brush on the other.

[Rick]

THIS works very well to make certain each spring is even...

[Big Booty]

these work very well to make certain each spring is even....

 

I like it.  I think I have a jig in the making with a slight improvement that gets rid of the fiddlestick altogether. Replace the vertical dowel closest to the spring post (in your jig) with a horizontal rod that presses onto a digital scale.  The horizontal rod can run in some brass tubing and you cut the length of rod so that the spring sits as it would in the motor.

 

Are you onto it?  I'll buy the first one off you....save me making it myself.