My Dynamometer Information and Pictures

(If you click on any of the images for a bigger picture, just click the larger image to close the window.)

The following pictures are of my prototype data aquisition unit. It is based on a Parallex Basic Stamp 2IC (tm). Supply voltage is from a 12VDC plug pack. Input from the drum is via a proximity switch. A disk with two tags is mounted to the drum that is the proximity target. The signal is isolated by an opto-coupler then it is fed into a flip-flop chip that give the "stamp" a nice 50/50 square wave. The duration of the "on" pulse is measured by the stamp and transmitted as a hex value serially. A MAX-232 chip converts the 0-5volt to the RS-232 -12V / +12V standard. My front-end receives this data and calculated the drum acceleration from this data and then converts it to power and torque values and finally graphs it. I have the PDF datasheets for the components I used here >> PDF album.

The complete prototype unit with plug pack, and serial communication cable.

Click on the image for a larger view (583kb). The full size image gives a clear layout of the components.

Due to the amount of email requests I've been getting for a component list for my data acquisition unit (which I don't have, as this version is about the 6th or 7th one and each one is just an expansion of the last version) I'll just explain what I did.

If you click for the larger image you can read all the chip nos, all I did was download the pdf data sheets for each IC and build the neccessary circuitry around each component. There aren't many components. The BS2 micro, a MAX232 RS-232 line driver, A 74HC74AN flip flop, a PC817 opto-coupler chip to isolate the stamp inputs, and a 7805 +5V voltage regulator. I have the PDF datasheets for the components I used here >> PDF album.

The resistor and capacitor values were chosen according to the data sheets. The only other additions I made were the jumper pins, just so I could pick between PNP or NPN inputs and another set for the DB9 comms connector so I could re-program the Stamp while it was on the board.

Here are some pictures of my "drum". I bought a length of 460mm diameter round bar 600mm long. I then got the sides machined down to 80mm X 120mm stub axles, (do you think I feel sorry for the machinist that had to sweep away approximately 150kg of swarf from each side?). I also had the surface machined with a cross hatch for traction. All radii were specified by me. I ended up with a drum 360mm wide with a diameter of 460mm and 2 X 80mm X 120mm stub axles. Final weight came to 478kg, raw weight was 780kg.

Side on shot of the raw bar.

Head on shot of the raw bar.

The round bar has been machined into a drum.

This is a dimensioned drawing of my drum.

This is a dimensioned drawing of my drum with bearings fitted.

No.1 Apprentice with the drum in it's bearing housing

Drum with its bearings fitted.

I had to be able to move this drum around, so I built a portable home for it. Here are some pictures of my dyno trailer. I had it weighed (sans drum) and registered, so now I can cart the thing around.

The finished trailer top view with the ramp down.

A rear shot of the trailer with the ramp down.

Ramp up, front view.

Most of my initial testing on the dyno was done with an old KLR 250. It got to the stage where I had to accelerate and spin the drum a bit faster than the KLR could. The old KLR wouldn't redline in 6th on it. It spun the drum faster in 5th gear.

The TL strapped to the Dyno with Gavan on it.

Side shot of the TL strapped down on the Dyno.

Head on shot of the TL on the Dyno.

I did a lot of my initial software testing with this Variable Speed Drive hooked upto a small 3 phase motor. Attached to the motor is a disk with flags on it that were the target for the proximity switch. I set the drive up for a maximum speed in RPM that was close to what I'd expect my drum to spin to. I set the acceleration time from anywhere from 10 to 20 seconds and recorded runs this way. I wanted to be pretty sure everything would work before I spent some $$$ on a real drum.