User Rating: 3 / 5

Star ActiveStar ActiveStar ActiveStar InactiveStar Inactive
dyno sketch

So what do you do when it's too cold for racing? Upgrades!

But how do you know if the upgrades are really an upgrade, especially if you can't run it and check your times? Then you'll need a dyno. Please forgive the poor quality sketch, it's about the best I can do to show what I'm building, this will obviously be a multi-part project. So far what I have are a couple of 3.5 inch diameter conveyor rollers, a couple of links, and some thinking. I need to buy a pump, valve, fluid tank, hoses, hose adapters, pulleys/gears, and a bunch of steel to weld up into a dyno.

The first link goes into pretty good detail about what, how, and why you build a brake dyno Karting Dynos part 1 This is a 6 part set of articles that you really should read.

 The next link helps you along even more YourDyno Check out the page on how to select a pump and definitely watch the video of them using one of their dynos:



And definitely check out the sensor box they sell, I will be getting one of these eventually. Just need to get mine working before I invest in the sensor package.

 Now on to some math! The rear wheel is about 18 inches in diameter. The rollers are about 3.5 inches in diameter. These compute to 56.52 inches and 10.99 inches in circumference (respectively). That's roughly a 5.14:1 ratio of roller revolutions to tire revolutions, that's a lot of speed difference between the too. So going to need to make a reduction gearset to drive the pump, most of the pumps I'm looking at have a maximum rpm of 3600 which might need a 2 or 3 to 1 reduction. Mounting a gear or pulley on the pump should be fairly easy, it's designed for that. Mounting the smaller gear or pulley on the roller is a much harder task. These are idler pulleys that I bought, they just have a shaft and bearings. I'll need to attach the smaller pulley directly to the 3.5 inch diameter roller, that means my pulley/gear size is going to need to be around 5 inches to clear everything and give me room for bolts. The other concern is the quality of the bearings in these used rollers, will they handle more than 10,000 rpms? I really need to sit down and turn the motor over while watching the markings on the flywheel, count the number of crankshaft revolutions until I get a full rear wheel revolution in both 4th and 5th gears. Then I can figure out how many revolutions per minute at the 10,000 rpm red line and determine just how fast the rollers will be spinning. Then I can determine the reduction ratio I need, as well as the direct I need the pump to spin. Then I can start buying materials.

 Thus pretty much ends part one. Hoping to have real materials to show off in the next part, but that may be slow going because it was 31 degrees F tonight, not really a good temperature for welding with my little flux core 110 volt welder.