[jeremycobert]

similar to a magnet marshal , I created this to test downforce. This is my 3rd prototype. Its running with my code for a STM32 board and runs on a usb power source, so you can plug it into a usb batter pack if you need it portable. I also added screws to the bottom so you can have the downforce match a know scale like a magnet marshal as the pic at the bottom shows. All the non electrical parts are 3d printed and I plan to tweak a few things in my 4th prototype.

 

[Kevan]

Can you tare the cars weight so that the reading only shows magnetic effect?

 

[jeremycobert]

Can you tare the cars weight so that the reading only shows magnetic effect?

yes, the 2nd pic is the tare weight of the car with no downforce.The orange button tare's the scale. The top pic is the full magnet downforce. in our club, TransAm era cars have a downforce limit of 150 grams.

 

[Sloter]

Nice!

Bob

 

[Kevan]

150g of magnetic downforce is HUGE!!!

...we have a 25g limit

 

[Sloter]

We used to race 350g with vintage Nascar - Revell/Monogram.

Bob

 

[jeremycobert]

150g of magnetic downforce is HUGE!!!

...we have a 25g limit

we only have 1 magnetic track in the club at this time. we have 8 classes to race, 4 non mag, 4 mag.


Trans-Am 150g in any location.
GT175 grams maximum.
Scalextric Stock Car 225g
Modified Sports Prototype 400 grams maximum

yeah, 400 is a bit much but there was a time when we had no magnet limits.

 

[dangermouse]

150g of magnetic downforce is HUGE!!!
...we have a 25g limit

I would imagine that would hardly be any magnetic affect at all?? We don't regularly measure cars but at a recent race we ran some Scalextric BTCC cars - it seemed a stock car out of the case had around 150g downforce and some of the guys with tuned cars had well over 200g - we had a bit of a chat about where we would go with that given the huge difference.

 

[MrFlippant]

I would imagine that would hardly be any magnetic affect at all??

Pretty much motor downforce only, so yeah, practically magless. We usually set a limit of 15, but on rare occasions a motor will pull a little more, but we don't make a big of it.

 

[chrisw]

150g of magnetic downforce is HUGE!!!

...we have a 25g limit

I would imagine that would hardly be any magnetic affect at all?? We don't regularly measure cars but at a recent race we ran some Scalextric BTCC cars - it seemed a stock car out of the case had around 150g downforce and some of the guys with tuned cars had well over 200g - we had a bit of a chat about where we would go with that given the huge difference.

25 gms is somewhere between 25 to 30 % of the weight of most cars out of the box, and is significant,.......try running your car magless on a plastic track against a competitor who has 25gm. of magnetic downforce and see who comes out on top..

Another way to look at it is,....playing with 25gms. of lead weight, can make a very big difference on how a car performs.

Cheers
Chris Walker

PS We have a couple of magnabraid tracks among our local clubs' , and motors generating even 10gms. of downforce do make a difference.

 

[Kevan]

Yes we're a strictly no-mag club, the only mag effect is from the motor and anything over 25g magnetic downforce as measured on our simple mag checker requires steel shim on the bottom of the motor or even on top can reduce it by up to 10g.

Typically an NSR King pulls 35g mag effect on our checker.

 

[GRUNZ]

Just to be clear, that 150gr is with the magnet in the car, right?

 

[RichD]

Here is a downforce tester that I made for HO cars. It is patterned after the ones that my 1/32nd scale club used before they switched to routed tracks.

The mild steel bar can be shimmed to change the sensitivity of the scale. I thought that using such a wide bar would make the device less fussy, but the cars must be carefully positioned to get consistent readings. For HO cars the Doane Digi-Tune scale might be the thing to use. For HO Gravity type cars there is a simple go/no go test that uses a standard steel cylinder. If the car can lift the cylinder it fails the test.

 

[Kevan]

Mag testers are all well and good but metal track or magnetic braid isn't a solid chunk of iron so the readings on the testers isn't going to be the same as the car on the track.

 

[jeremycobert]

Mag testers are all well and good but metal track or magnetic braid isn't a solid chunk of iron so the readings on the testers isn't going to be the same as the car on the track.

It does not need to be compared to a track. The tool is used to compare cars and their downforce. As long as all of us are testing to the same scale, then all cars are balanced vs each other.

 

[Sloter]

Mag testers are all well and good but metal track or magnetic braid isn't a solid chunk of iron so the readings on the testers isn't going to be the same as the car on the track.

It's a measuring tool so you can compare one car against another. I have a Marshall Magnet and it works great as a set up tool as well as a tech tool. Same as the tool pictured above.

Bob

 

[Kevan]

It does not need to be compared to a track. The tool is used to compare cars and their downforce. As long as all of us are testing to the same scale, then all cars are balanced vs each other.

It's a measuring tool so you can compare one car against another. I have a Marshall Magnet and it works great as a set up tool as well as a tech tool. Same as the tool pictured above.

Bob

Obviously I understand that, my point being 150g reading on the tester won't equate to 150g on the track.

 

[RichD]

With respect to HO T-jet type cars there was a controversy several years ago because it was believed that certain people had magnets that were not available to everyone. It would not be very practical to take gauss readings during a pre-race tech inspection. A device like the Digi-Tune would be a better solution.