# Dyno



## sidejobjon (Jun 3, 2010)

Was there directions to build a Dyno?
Or not worth it?
SJJ


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## Dyno Dom (May 26, 2007)

SJJ, many racers find them to be quite useful and there are a few commercially
available. You can also contact Dyno of Ct here on HT. He has built some
elaborate Dynos for his racing/testing.


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## Dyno Dom (May 26, 2007)

Does anyone have experience/used the Laser Tach by Paul on auction site??


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## Boosted-Z71 (Nov 26, 2007)

There are several dyno threads on here, I have built my own and used several others. The key that I have found is that comparing dyno 1 to dyno 2 numbers means nothing, for most units comparing dyno results to the track reult is a hit and miss deal. 

I found that torque is what matters, you need to be able to load the car on the dyno for any chance at a result that will tell you what is going on. On mine I measure, RPM, Wheel speed, amp and voltage draw as well as voltage output from the slave motor. Results are also dependent on how you interpret the data, a case in point, on the dyno it may show that increased spring / shoe tension shows more RPM and slave output, on the track the car slows due to minor handling problems, its all a compromise. That being said a good dyno is great tool for initial testing / tuning on a car, but to fine tune it to the edge, nothing beats turning laps, watching and listening. There are several out there, each measures different characteristics the builders believe to be key to a good tune, your just going to have to feel your way around to find the one that works for you.

Boosted


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## Bill Hall (Jan 6, 2007)

Boosted-Z71 said:


> ........Results are also dependent on how you interpret the data, a case in point, on the dyno it may show that increased spring / shoe tension shows more RPM and slave output, on the track the car slows due to minor handling problems, its all a compromise.
> 
> That being said a good dyno is great tool for initial testing / tuning on a car, but to fine tune it to the edge, nothing beats turning laps, watching and listening.......
> 
> Boosted



Solid gold!


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## alpink (Aug 22, 2010)

what boosted said.
and I do have a laser tach dyno which works good for what it is, but there is no way to load. and when you let the power off, the car flies backwards off the cylinder because the cylinder has so much momentum.
certainly not worth what I paid.
anyone wants to buy the laser unit PM me and make a reasonable offer. I also have nearly all the components to build two of them less a cylinder. the laser tach for automotive use weren't too expensive and not terribly difficult to find.


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## rholmesr (Oct 8, 2010)

I like my tach. It works pretty good for me and the answer it gives lines up well with the ol' "Ear Dyno" too. To me, it is a mighty good tool to help tune a car and quantify how fast it "ought" to go on the track. It isolates the variable "top end speed" very well. It will also show you if the car wheels are set up well - if they're running true or not.

Here's a video I made for my tach:





Obviously there are lots of variables to consider to determine the actual final speed you see on the track. For example, the pickup shoe settings have an enormous amount of influence on the performance of a slot car.

I'm not a real big fan of using a dyno (i.e. driving a DC motor as a generator and reading output volts). In my experience the volts value does not correlate nearly as well with the actual top end speed of the car as does the tach reading, and it's somewhat variable in that the answer it gives is dependent upon how warm the generator arm is and how well it's lubed. Then again, the only dyno's I've ever used were home-made ones and maybe the professionally-made ones work better.

The usefulness of a dyno or a tach depends a little bit on your driving style and the track you're running on too. If your track doesn't have long straights then the car is never going to come up to top speed anyway and in that case more torque can be a real benefit. On the other hand, if you have a track with 20 foot straights, then top end speed is the name of the game.


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## Rick Carter (Dec 2, 2008)

Boosted,

You hit the nail right on the head. I couldn't have said it better myself. I've had 2 Dyno's and got rid of them because it (to me) really didn't mimic on the track what the readings showed.

I just use, as I've always had, my Wrightway mini power supply to check my amp draw and listen to my gear mesh and then fine tune from there on the track.


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## Hornet (Dec 1, 2005)

I like your tach set-up R ,looks good :thumbsup:
Rick


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## Boosted-Z71 (Nov 26, 2007)

Al if your roller is steel or you can figure out a way to put a magnetic surface on it somehow, you can easily add load without adding frictional drag to the roller asm by using a ceramic magnet placed near it to add the load, more magnets, more load. 

I did this to my dyno while playing / testing around with different types of load. First I tried friction on the roller, that was poor at best, I tried a gear reduction, still little or no control over the load. I did all this because all the dyno's that I had used, including mine would not truly identify the track dog. I started playing around. I added the load and then the dyno will identify the track dog, as well as the track leader. 

Hornet has tried this and he is a believer as well. 

I have a set of parameters that I measure to with the dyno, If I put a car on that maxes the scale I add more magnetic load, I try to load to get a baseline line run in the middle of the testing parameters window, that way I can easily see gains or loss. You have to remember were talking about a very small incremental result for gain or loss. Its a simple setup and very adjustable, as you will find that most in-lines need more load than t-jets, and modifieds are another story altogether, I also have the 4 amp power supply adjustable from 5 - 20 volts, and try to test at whatever voltage matches the track. 

Boosted


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## Hornet (Dec 1, 2005)

Adding the magnet to the load was Boosted's idea,but i'll back him up,it works:thumbsup:

A neo mag is now a perment attachment to my load-able slave.
Rick


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