[LMP]

Is there any way I can measure the power of a magent using a more precise method than my own judgement?

If not, are there classes of magnets? I'm just thinking, once I get club racing, I'll probably want a bit more or less magnet. Is there any way to do this without trial and error?

Example:

Fly magent is too strong, but I don't want to be sliding all over the place. I want a magent less powerful than a fly but more than say, a ninco.

Just an example of course, but I hope you get the idea.

Thanks.

 

[GRAH1]

I use a digital scale with a steel top fitted the car sits on a bridge over but not touching the scale ,i can then read a negative gram reading this allows me to compare one car to another

 

[Nep72]

Well, the scale method is the "standard" way to know differences between magnets. There's also a "pro" way, that is, with a magnetic field meter (Gauss meter). There's a copulpe of chips, 3515 / 3516 from Allegro (no advertising aim) with a direct output reading of 1mV/Gauss and 2.5mV/Gauss respectively. You just need a +5v power supply t ofeed the chip, and a (preferred digital) voltmeter to know the exact magnetic field strength for each magnet. You can even search for the best magnet to be installed into motors to reach maximum torque. These chips usually cost around 10-12€.

Cons: Since magnetic field is very variable, it depends on magnetic conductors around the magnet (case, rails...) and meter window in this case is very small, you have to run several readings to get an average. This problem is not so important with the scale method but you will get small differences depending on magnet position.

Hope this info's not boring anyone.

 

[LMP]

so with the scale method, the magnet effectively brings the top plate up, giving a negative readng on the scales?

kinda like that terrible diagram?

 

[Nep72]

Yes. But make sure that magnet is always in the same position or readings will not be true.

 

[LMP]

OK thats great. Thanks!

 

[Xlot]

Hola Nep,

very interested in the Gauss meter - I understand that in Spain it's commonly used to make sure motors are not too "open" and act as magnets on the rails

BTW : isn't Gauss metering one of the functions of DS's Pocket Checker ? I don't remember it being featured in one of your excellent reviews on Slotcenter

Ciao
Beppe

 

[Nep72]

Hi Beppe! Nice to read from you!

Yes, it's common to search (and "open", illegal) motors to find best magnetic field against rails to keep car stuck to the track, since races are without magnet.

If you want a Gauss meter just send me your address by mail, I'll be glad to send you the electronics. Just add a digital voltmeter and a power supply.

Yes, Pocket Checker has two fatures: RPM reader and Gauss meter. Problem with earlier versions were that Gauss detector was not correctly installed, so you can find big differences between readers. This problem seems to be solved in v2.

No, I've not had any Pocket checker in my hands yet. Maybe Marcel wants a test for GSR, or David for Slotcenter ;-) No advertising aim for mentioned brands.

 

[astro]

Are those DS pocket checkers any good? How much are they? Cab you get them in the Uk?

 

[Nep72]

Well, you can find DS products almost everywhere... in Spain. I think that spanish dealer is "Cric-Crac", you can contact them via their web page; here is the article: Pocket checker. Pirce is usually around 90-100 €. No advertising aim.

 

[astro]

thanks

 

[LSIntegra94]

In the page for the Pocket Checker it says "Pocket Checker Medidor De Gauss Y Rpm". Does it measure motor rpm and how?

 

[Nep72]

Yes, it measures RPM. I think sensor is based on a emitter/receiver light beam, so you have to paint in white a part of the pinion/wheel you want to measure. But I'm not sure now. Pocket checker was tested in Más Slot, I can check this evening and tell you exactly how it runs tomorrow.

Yes, sensor is optic, you need a black and white cylinder to read rpm's, or stick an adhesive with these colors to the wheel.

 

[Tropi]

My method is very similar to Graham's, except that I prefer a piece of actual track to be used as the attracter for the car's magnet. 'Stick' the track to the top of the scale by use of a pair of weights - crude but effective and non-destructive.
See more on this HERE.
Different makes of track and even different pieces of the same track can vary enormously. I am sure Grah's method will give much more consistent results, but I feel somehow happier seeing figures that relate to the terrible inconsistency of the actual track rather than the slightly idealised condition of a nice sheet of steel.
I guess using both methods should cover all angles.

 

[Scott B]

Here's a link to a feature on one I saw first hand last year in the USA.

Matthew Wilders mag-strength scale for even racing

Matthew is a member of HOST (Home Operated Slot Tracks) and one of a number of guys who I met last year.

Scott

 

[IMMT]

We have built three of Matthew's scales for our club. All three scales are consistent and it's an easy and accurate tool to measure your magnetism.

 

[Tropi]

I would be very interested to see if anyone has any actual eperience of the DS pocket checker. This item has been talked about for perhaps a couple of years to my knowledge but I have yet to read anything practical about their usefulness.

 

[Fergy]

QUOTE easy and accurate tool to measure your magnetism

I usually use a lady for that!

....sorry.... couldn't resist!

Tropi, I too have never heard anything of substance re the DS unit. Makes me wonder.....

Most guys I know use a home-brewed system like the ones previously described. Absolute measurements really don't matter if you have a system in place that is consistent - relative measurements are all you need!

 

[Nep72]

QUOTE (Fergy @ 16 Apr 2004, 05:39)...Absolute measurements really don't matter if you have a system in place that is consistent - relative measurements are all you need!

Fergy,

Since one of the illegal tricks done in Spain is replacing motor magnets for more powerful ones, people who verify cars need a tool to read an accurate value to be measured anywhere and create a "standard".

They tried to use DS but, as I said before, it's not accurate enough to create a limit value, two different DS magnet meters show different values for the same motor.

Last november Ninco used the scale system to detect illegal motors in the "11th slot-rally de Lloret-Costa Brava", but no one at home can reproduce the same value unless they have exactly the same pieces used on the scale used as "standard".

Of course I agree with the idea that you don't need an absolute magnet meter... unless the race regulation says that "limit value for magnet in the motor is 250Gauss faced to the track", and this happens in Spain.

 

[Fergy]

Nep, I understand the dilemma when rules state specific values. My comments were geared more toward the typical racer who simply needs comparative readings.

To get accuracy, you need a proper gauss meter, properly calibrated, and good ones can be a bit expensive for most racers. Even the calibration of a good unit can be a problem unless you have access to a very accurate reference, or access to a reference that will be used in enforcing the rule.

One trick used in HO racing was to specify that the magnets could not pick up a specific metal object - if they did, they were illegal. Choosing a cheap, common metal object allowed everyone to have access to a "measuring device". One such object was a hitch pin for a John Deere tractor! Crude solution perhaps, but it served the purpose.