Simple RPM Test Rig

[HomeRacingWorld]

Decided to build my own small motor RPM test rig.

Thanks to DRW21 for making me the first motor disc. I made the second one using an old NSR spur gear and sleeving the inside with a brass tube.

Very simple using the laser RPM checkers you find all over Ebay and the like.

1x4 scrap wood stacked for the discs on the end of the motor to clear.





The motor cradles were made of sheet styrene plastic and Super Glue. My granddaughters have "spare" tiny hair braid thingies (official nomenclature :) ) And those are glued in place as well.

Works great. Yes, I am sure there are those who do not think these checkers work well, but they do. I have bought several and all of them work and report the same numbers.

I was testing a new motor I ordered for the Scalextric/FlySlot/Policar Grand Prix models. I found one that has milder RPMs yet still quick enough for fun.

Policar FF050 - 25, 400 @ 12V
Scaley FF05 - 22,500 @ 12V
BenchTest Motor - 17,800 @12V

Anyway, fun to experiment and easy to build. These RPM checkers are very inexpensive at around $15.00.

[urbanwarrior]

I just bought one of these laser rpm tachometers. Is there any formula to figuring out the rpm's or is it simply the number that shows up on the screen is the rpm's?
This looks like a simple idea that's easy to make but one that I wish I had a while ago.
Thanks Harry and DRW21.....
John

[HomeRacingWorld]

Just what shows on the screen. Just have to keep the TEST button down. That's the only downside is there is no button "lock". But no big deal, I hold the button for about 20 seconds and it gives a good reading average.

[Z-carfan]

Great info Harry, I have been thinking about one of these. Hmm, where is my eBay link....


Sent from my iPad using Tapatalk

[ccobra]

Wow, great idea. I can see a small dyno coming from this to check your gear ratios. Thanks for the insight on this Harry. Now to find a tach.

[TuscoTodd]

Now what is pretty darn slick!
Thanks for sharing Harry! :D

[buspor63]

I've done the same thing, but using an old Futaba servo wheel glued to a Carrera pinion. I'm going one step further and have built a jig to hold the motor above a digital scale, I wonder where that could be going?

[HomeRacingWorld]

You are welcome.

I guess you are going to start torque measuring. That'e how Mr. Livingston taught it.

[Audi1]

Nice set up, Harry. Would be interested to see how the H&R Hawk measures up. I use a similar system, although it's hand-held. I find that particular motor typically underperforms; although it's cousin, the Jack Rabbit, almost always overperforms.

You can also get an idea of how to set this up by googling the Austin Slot Car Club; they have a series of useful how-to's.

Allan

[chappy]

Great set up Harry, I might steal the idea for my new work area.
it sure beats my plasticine and rubber bands method for holding things together.
Thanks for the share.
Bob

[chappy]

Harry , quick question, for you.
What is the distance you used between the tach and the motor, and how significant is it?
Cheers
Bob

[HomeRacingWorld]

Right about 4 inches. Not certain on the significance. It says up to 6 feet. I used this distance to make the rig as portable as possible for my bench space. I tested it at 3 inches and at 1 foot and no difference. Just made sure the laser is slightly off center and hitting the center of the disc.

[DRW21]

Very cool test set up Harry, I like the motor cradles you made from styrene, too simple.
These tacho's do come in very handy for choosing motors.
Ya'll need to get one.

[HomeRacingWorld]

Posting additional info as requested.

The test discs were made 2 different ways:



The first was custom made by our own DRW21 for standard 2 MM motors (Piranha, NC Types)

The second was made by myself using an NSR gear.

I used the NSR gear as it uses the larger standard .050" screw opening. I carefully notched the tubing before installing it inside the gear. It was a snug fit and no need to solder or glue.
Then I just placed the gear on some scrap styrene plastic and cut it out. Painted flat black, and then the reflective strip installed.

Hope this helps.

[HomeRacingWorld]

Bump by request