# HO Slot Car RPM Tool



## buzz67 (Apr 9, 2007)

I hear a lot of this talked about, yet no one will ever explain where to get one or how one is made. I would love to be able to test the speed of my t-jet motors. Sound only gets you so far. Can anyone offer some info?


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## mking (Apr 25, 2000)

*often called a dyno...*

Basically it is an electric motor that is rotated by your slot car. Either the slot cars driven wheels drive a slave wheel that is attached to the electric motor, or you couple the driven axle of the slot car with the shaft of the electric motor (either works). The mechanical power transferred from slot car to the electric motor (the energy rotating the electric motor) will generate electricity (the same way electricity generates mechanical energy when you run a slot car, the process is reversible). You hook the electric motor to a digital or analog meter to measure the amount of electricity being generated. The more RPMS your slot car motor transfers to the electric motor used as the dyno, the higher the reading will be. 



I have 2, but never use them. Instead I just tune and run laps and time the laps. But I do know others like dynos. If you’re interested in trading or buying on of my 2 dynos, let me know. 



Mike


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## noddaz (Aug 6, 1999)

Funny thing..
I have one at home that I have had for over a year and still have not put it together...


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## buzz67 (Apr 9, 2007)

Thanks for the info. I was pretty sure already how a dyno worked. Does anyone have plans for building one? Is this something that is out there? I have seen vintage ones before used for larger scales, and even a newer one made for 1/32 that has a built in gauss meter also. 

I currently use the "sound" method. It’s obvious when you have a good runner. I use lap times and test and tunes, but its very subjective. A fast motor means nothing if the rest of the car is not set up for track conditions. I am very methodical in my approach to building my cars. I like to get the motor tuned first, and then play with shoe travel and “ride height” afterwards. So you can see a dyno in this instance would be helpful.


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## videojimmy (Jan 12, 2006)

I don;t know if this will work, but I read that you can oush the rod thriugh the arm on a tomy motor, hook two wheels to it and then run the wires to a meter.. in throey, when you tocuh your cars spinning wheels to the tomy motor, you will get a reading on the meter

again, I have no idea of this works, it;s just somethig I read on one of these forums


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## mking (Apr 25, 2000)

*here is a dyno pic*

along with a description of the parts used to build one

http://www.howorld.net/pages/archives.html


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## buzz67 (Apr 9, 2007)

I looked all over the HO world.net page and I cant find anything on dyno's


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## buzz67 (Apr 9, 2007)

buzz67 said:


> I looked all over the HO world.net page and I cant find anything on dyno's


I think I may have found it hidden within another write up. But it didn't have have instructions.

http://howorld.fsmra.com/archives/harris/harris.html


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## mking (Apr 25, 2000)

*hey buzz*

that is the article i was trying to link to, and your right, other than a parts list it doesnt describe building the dyno

mike


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## Bill Hall (Jan 6, 2007)

*The dyno-saur*



mking said:


> snip*....I have 2, but never use them. Instead I just tune and run laps and time the laps. But I do know others like dynos. If you’re interested in trading or buying on of my 2 dynos, let me know.
> Mike


Like Buzz and Mike, I set them up and put'em to the track. IMHO, The so called dyno of the era was a superfolous gadget designed to extract a few more dollars from the consumer. Did someone ever make a good quality, calibrated unit for HO cars? 

It is the overall response of an armature through the RPM range that I'm looking/listening for, and not necessarily a single specific number like final RPM. Like 1:1 cars it's the difference between quick and fast. I'm more concerned how quickly it gets on the pipe. Every arm has a personality so to speak. Especially our beloved pancakes. Good bottom end, good top end, middle of the road, and all points in between. 

I'm a brontosaurus. My eye's ears and hands tell me what is to be. During a free spin test of armatures my hands tells me how the ballance is. My ears tell me what the response is. From there I can ball park the gear setup, or throw it in the core pile! 

Once on the track my eyes and ears tell me what to do regarding shoe tuning and tire profiles. For a "dynosaur" like me there is no substitute.


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## roadrner (Jul 21, 1999)

Buzz,
You have the first tool already. Your ears. Next you have a pair of hands that have ten digits. You'll be surprised how sensitive they are. That's as good as that plastic thing a ma jig that was retailed back in the early days. Guess you just need to, pardon the pun, feel the force.  rr


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## Malteze (Apr 6, 2007)

I just got laser photo tachometer on ebay for about $20. I havent got to test it out much yet, but it seams to work. id like to make a stand for it or something to make it more hands free. I check rpm on the wheel. Measure the tire. then i can calculate speed. make adjustments to the car and repete...


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## Hornet (Dec 1, 2005)

Here's a pic of my rude and crude one,made for magnet cars
http://www.canho.ca/modules.php?name=Forums&file=viewtopic&t=153


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## slotking (May 27, 2008)

having used a dyno for many years, I have found it a great tool from t-jets to the fastest magnet cars.

I do not use it to compare car 1 to car 2, but to compare each car to itself!

So if I do make a change on brush tension or gears, or oil, I can see the results!

It great to use for testing gear plates or just arms in a t-jet!
makes the testing much faster than putting it on the track.


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