This post is about an idea. An idea I had while on vacation at the beach in 2017. I haven’t talked about this much because it was just an idea and ideas are funny things. They are not really real, until they work. Until that moment, when something actually happens they are just a collect of thoughts, some parts, a design, and maybe some equipment. But not real. So unless you stumbled into this lost corner of my garage sometime over the last 4 years or were another racer there wasn’t really much to say.
In 2017, I had just returned to racing and while on vacation ( see vacation photo as proof I do occasionally take vacations) I decided that we needed a way to test an engine without actually putting in a car and driving on the track. We needed to test it before we got to the race. Now every racer knows you do that on a dyno. Dyno is the short name for Dynamometer – a device for measuring force, torque or power and they are crazy expensive. Even just renting time on a dyno is hundreds of dollars an hour. But I do not require all the workings of a full dyno shop just to test our small 1-2 liter motors. So I designed a test stand that could be used as a dyno.
I didn’t know anything about building a dyno, or how they work, or even how to weld. Really I knew nothing but had an idea. But that was enough. Like the Vacuum Former and the CNC projects before it, I just needed an idea and time to follow it through. I started collecting bits and parts. A pump here, a transmission there, an extra this, an extra that. To make a motor run without the car you still need all the systems of a car. The fuel system, the electrical system, the hydraulic system, the cooling system, etc. I would say it’s just as much work as building a car, it just doesn’t go anywhere. Over time (the last 4 years) it has come together.
Today we tested the pump. It worked. We successfully pumped water with a car motor. Now that doesn’t sound all that impressive. Why would you want to pump water with a car motor anyway? Well, we pump water because it is Work (physics definition of Work) and it is Work we can measure. Like MPH, RPM, or 0-60 it’s force and power. In the weeks to come the motor will run, the pump will turn, the torque will create force on the load cell and it will no longer be an idea. It will be an actual working Dyno machine.
It’s been a journey. I’ll post some of the steps and phases that lead to here. I hope that some of you have ideas that lead to things that work too. Happy workshoping.
The control column on the Dyno has to be all things. It’s you power, fuses, gauges, hour clock, throttle, clutch, fuel system, and note pad in one. Additionally it needs to move. Designed to be wherever you need it. Exhaust on the right side of the motor? No problem, move the controls to the left.
Like some other projects, I chose to use some CNCed Plexiglas and color from the back. I made the top hinged so you could pull two pins and easily get to the back. It has a full complement of gauges (Rev limiting Tachometer, Oil pressure, Water and Oil Temp and Air Mixture). Also the usual toggles for fuel, coil and fan. We strive for everything to be just like the racecar. Just what you need and nothing else. If we use something different on the Dyno then we do in the car then you are not going to get the same results when the motor goes in the car. We don’t want to be tuning for the bench.
The fuel tank, pump, pressure regulator, and gauge are all on one support frame. With just a few bolts they can be removed as a unit. Again I have gone for a unitized system design. Easier to fix and diagnose. The tank was a hard one to find. There aver few small metal tank options. This one is a vintage steel tank from a 70’s riding mower.
The throttle is a marine style. Since this is a standing position a foot pedal didn’t make much since. It’s another vintage find. Most new ones have gone to drive by wire and they don’t use cables anymore. I had to build up the mount from scratch to fit it in on the side of the panel. Also had to design and 3D print custom parts (grey in the photo) to make the linkage work.
The heart of the Dyno is the Pump. There are two ways to measure motor output, with load (pump or drag break) or electricity. Probably the easiest way would be to measure the wattage output and this would be done with Eddy Current brake (Telma retarder). Not being able to find one of those, I opted for the water break and load cell. If you want to know more urge you to read up at YourDyno https://yourdyno.com/brakeabsorber-dynos/
The principle is simple. Create load, measure force from load with the load cell, calculate the end result. Is it 100%? No, but really you don’t need it to be. It is a loss loss system anyway. What you need is to measure change in load over the arc of the RPM of the motor. If you want to know if your carburetor changes helped, then the measured curve of this run vs the curve of the last run is what you need to know. Did our tuning make the motor stronger or weaker? Knowing if it generated 110hp or 111hp doesn’t really help, it just a number.
Where did I get my pump? I have no idea. It was salvage someone else was getting rid of because it was all locked up. I.E Free! When I took it apart, it turned out to just be full of mud. I think it’s an old farm pump for pumping out pond or lakes. For our purposes I have mounted it on bearings. One front and one rear. This mean the pump is free to swing or pivot. We hold it in place with the load cell. That then measures the drag applied when we close down the valve on the output shaft. A 55-gallon drum provides the water, which just circulates in and out. Simple, right?
Not so much. Not know who made the pump or where it came from means no parts and you get to make your own replacement gaskets. In fact I have had work out all the details. If there is any part of this I’m not sure about, it’s the pump. If I can’t make it work I’ll have to find a truck scrap yard and a Telma retarder. But since the frame design is modular, I can just swap these parts and the rest stays the same.
I was supper thrilled when we were able to pump water. It means that the pump is good and likely to do the job we need. Happy workshoping.
Look for the other articles in the series DIY Dyno Frame and Dyno Load Cell.
The design for the Dyno’s frame is around the idea that everything is moveable and modular. Because we plan to test different engines and they come in different sizes, the parts of the dyno move along the frame to the best location for the motor being tested. Also it makes changing motors easier. For example, the radiator, fan and oil cooler unit comes off with 2 bolts. That gets those components out of the way during a motor swap. The same is true for the control panel and fuel system. We plan to test 1-2 liter BMC, Lotus/Ford and Miata motors. So, lets start there.
To calculate the frame size, I started by lining up the components in the order they needed to go and measuring everything. See photo 2. That gave me a general width that the frame needed to be. Then it was trip to the metal supply depot for several 10’ (I discovered that is the industry standard size for raw steel) lengths of 2” square steel tubing. Another stop for some heavy-duty steel casters. Once I got that home it was a kind of a “now what?” moment. I really didn’t know what to do next.
I remembered my dad had an old Craftsman stick welder out in his garage under 20 years of dust. I borrowed that. Bought a helmet, gloves and other supplies at Harbor Freight on the way home and was off to the races.
No, I wasn’t. I learned I knew absolutely nothing about welding and you just don’t pick one up and lay down nice bead weld. There are about 100 ways welding can go wrong and I must have hit 99 of them. And no, you can’t learn it from just watching some YouTube. I tried that too. In truth it’s an art that takes years to get right and after 4 years of trying I still suck. But a friend that did go to welding school came over and showed me how to start a bead and a few of the basics. On a good day, if all is in aliment, I only have to grind off half of what I weld and start over. On a good day. Welding is a skill and one I may never possess. I have accepted there are some things I’m not good at (my taxes, singing, all musical instruments) and I should just hire those out. But I did learn enough that with trial, and error, and lots of grinding that I can get non-critical metal parts to sick together. It will never pass inspection but I’m not taking it on the road.
Look for the next few articles on the Dyno Pump and Dyno Load cell. Happy workshoping.