R P M

[one32]

Fellas
I have never went down this road before. I need to know what type of gadget I need to purchase, and where to purchase it , to read rpm's on a motor.
I have searched the hrw site , and have had no luck.
Any help would be appreciated.
Thank you

[4424ever]

There is a free rpm app for a smartphone not sure but I think it’s called Giri
It measures rpm by reading the sound of the motor and was accurate enough to trust on my other phone I should really get it again myself 🏁

[arroldn]

I use this as well. Sometimes it can be a little erratic but works well for the most part.

[waaytoomuchintothis]

A very simple and accurate laser tach is on Amazon. I'm on my second one in ten years, the first one had a battery leak that ruined it.

[Kevan]

Cheapo digital tacho like the one in the pic works well if you put a rotating disc on the motor shaft with a thick dark line on a lighter background.



'Giri - the RPM Checker' app works great out of the car, it helps if you slide the triangle on the screen to the approximate rpm range of your motor. Be aware background noise like in a club environment with cars whizzing round the track will make it very difficult to get an accurate reading.

Don't expect accurate readings with the motor in the car and gears connected.

[Aptosc6]

I use this RPM Checker. They cost around $15 and seem reliable but, eat batteries. Take the battery out between uses and they will last over a year.
Use a spur gear screwed onto the end of the motor to place your target on. It will bounce slightly but will not effect the reading.

[Kevan]

Putting a spur gear on with a 3/32 hole on a 2mm motor shaft isn't a good idea as it'll run off centre and will prevent the motor reaching peak revs. I glued a flat disc to a plastic pinion then trued the disc while the motor was running.

[Ragtopman]

I use the one in the pic and it works well

[jaws]

I use a Spur gear from NSR that is made for 2mm axles. I have a piece of reflective material attached on one side. I have a meter like in the picture used for the testing. Some motors have a double shaft, so I can test with the pinion on.

I also have the roller bench from SCC and can use this to check a car. I just attach a piece of reflective material to the tire/wheel and get a reading. Knowing the gear ratio, I can then determine motor RPM.

Jim W
Denver, CO area

[MrFlippant]

Something specifically for slot cars will be hitting the market soon.

[Henri]

do you have a crystal ball Greg??

[one32]

I like what you have going on there Henri
I may have to get in line for one.
All you need from me is an Email?
Thank you

[Henri]

thank you, i will answer your mail. Greetings Henri

[HomeRacingWorld]

I disagree. RPM ratings are useful, regardless of any gearbox.

It is a baseline start for any series. Our Showdown Series has been very successful just using one spec motor.

The numbers from manufactures like Scalextric, etc are not accurate.

But ones from say, SCC are. I know because I bench test boxes of them myself and we come to a number average.

I use the RPM meter shown above. I created discs for measurement. I do not check at the wheels.

Easy to discount simple methods when your trying to sell high end test benches.

[RichD]

The number printed on the label is sometimes off by a considerable amount. Some makes at least give consistent RPM readings but others can vary by a lot. I measure every motor that I buy, the older 18K Scalextric motors often measured over 23K. The latest Scalextric motors that I bought were only 20K and that was a problem because we had several classes that used that specific motor.

[REL13]

Here a picture of what I built to test RPMs.

[HomeRacingWorld]

And that's all you need 99% of the time. If that rating is what you are after, it works. And for about 20 bucks.

Pretty sure we already covered label ratings not being accurate.

Our spec classes run fine. If we have a rare slower motor, we simply swap it out. Too easy. Just make a simple test bench and problem solved.

A simple multimeter can tell you anything else you feel important to know.

Simple test methods are covered here by Robert Livingston in the SCN Motor list.

[Old Reb]

I have an RPM meter. I have found it necessary to shine a strong non-ac light on the rotating disk to get a reading that is not affected by the indoors ac lights. I have also found that the position and strength of the non-ac light source has a large effect on the RPM reading. It is very difficult to get consistent readings. How is everyone dealing with this? I am wondering if I am missing something.

[MrFlippant]

All methods are perfectly legit for however a given club decides to measure and set their limits. Some will set an RPM of the motor, some at the wheels, some at actual speed of the wheels, all of which will be different, but equally useful as a comparison and limiting tool. Some people like to DIY, and some don't. There are plenty of tools on the market that sell out instantly, which would be called overpriced by those who would do the same job a different way. The cost is for the convenience of a tool that is ready to use for the intended purpose straight out of the box. I'll take a thing that I can just plop a car on and flip a switch, over something that requires me to tear down a car, every day of the week.

Options are good to have.

[REL13]

I have not had that problem with my set up. I have checked the motors two or three times and got the same reading.