I'm wanting to build a chassis dyno...or actually have it most of the way put together. I had planned to use a handheld Tachometer but I'd rather come up with something different...Any ideas?

I'm using an inductive amp meter to set my current draw, that part is working pretty sweet, but now I want to be able to read the RPMS

Joe
Bring it to Bakersfield and let me take a look. I may have a solution.

Steve

Steve,

It's BOLTED to my workbench...it's just a rear pod, motor, axle, etc with a bank of resistors...blah blah...

I thought the hand held prop tachometer would pick up a signal off a WHITE DOT on the wheel...(I know I did that YEARS ago , but the tach I had then I believe sent a signal that bounced off the surface or something...I may end up installing something similar to an actual plane propeller for it to pick up. ( I remember those way back when too...)

Could you use the in car data recorder?

http://www.hobbyshopper.com/cdr.html

Hey Joe, have you tried to paint the edge white with black dots? Maybe the dots are too small? Wanted to see you on the 19th, but it isn't looking goood for me. See you at the next race.

Don S.

Don,

"IF" it rains Saturday, the race will be the following weekend...I know that will interfere with some people's EASTER plans...so I'm keeping my fingers crossed...NO RAIN~

And YES I painted the edges of the tire/wheel white. I looked up some specs on my handheld Tach and it says Flouresent lights emit a RPM signal. I may need to move my table into direct sunlight or put the tach in a covered box of somesort.

I may look into using a hall effects switch and see if I can put something together that way...

Joe,

You could put a motor on the pod and hook up a volt meter to it.Then you can tell RPM by voltage.Like the old PSE chassis dyno.Using that inductive amp meter would be really nice.The PSE had 3 switches to choose from and depending on the motor the amp draws varied.

Huff,

It's been years since I'd seen an old THOR/PSE dyno, but I do remember them using a couple of the old radio shack type DVMS. I never got to see what they did, but you are the second one to tell me to use the output voltage as my RPM reference.

higher rpm=higher voltage

There are a couple guys that still have them around here.Pretty sure that is how they work.A really good tool at the velodrome,you can find out how much gear the motor will pull.

There are a couple guys that still have them around here.Pretty sure that is how they work.A really good tool at the velodrome,you can find out how much gear the motor will pull.

hmmmm now HOW did you know what I was building it for..LOL

We still use them in stk and 19 turn for local racing and bench racing. The voltmeter can be used for both rpm reference and for amperage. Read voltage off of slave motor for rpm. Use a heavy solid copper wire about 2.5 inches long as a shunt. Install shunt in series with your power feed wire(powering test motor), positive or negative side. Hook onto each end of shunt with small wires for reading voltage drop across shunt. Use the milivolt scale on your dvom. you can calibrate your shunt by using your inductive meter. Just move your two wires closer together on the shunt to decrease your amp number and farther away to increase.

We still use them in stk and 19 turn for local racing and bench racing.

The voltmeter can be used for both rpm reference and for amperage.

Read voltage off of slave motor for rpm.

Use a heavy solid copper wire about 2.5 inches long as a shunt.

Install shunt in series with your power feed wire(powering test motor), positive or negative side.

Hook onto each end of shunt with small wires for reading voltage drop across shunt.

Use the milivolt scale on your dvom. you can calibrate your shunt by using your inductive meter. Just move your two wires closer together on the shunt to decrease your amp number and farther away to increase.

Thanks John, this gives me something to play with before the next trip to the VELO...