anyone ever made there own engine dyno, i have been thinking and it and it cant be that hard, something to put a load on the engine and a loadcell to give you a torque number. anyone have any thoughts on this?
A lot of algebra and physics, but it could be done. Mechanically I think it's quite simple, but the math is killer. Calibration is another item to think about. If you had a known weight and you hooked up the engine and accelerated the weight, you could calculate power needed to do so. But be prepaired to brush up on your physics. The weight could be the load you put on the engine possibly. I'm quite sure this is the basic principle of ch***is dynos.
It can be that hard. Consider the reliability and repeatability you'll have to engineer into it. The method by which you choose to load the engine must be consistent and safe, and then you have to determine how you'll read the torque. This should not be affected by temperature or stress, so when you do back-to-back pulls, you'll get reliable data. Oh, and account for weather differences in the air, too. It's not easy at all. Dynos aren't cheap for a reason - they're pretty trick instruments. ~Scotch~
I remember an artical in R&C around 57 where a guy used a big truck brake drum with paddles welded inside of it, and a cover for the open side, as his water brake. Then it's just a shut off for the water it pumps and a one foot long bar with a scale on it to read torque. A tach for RPM so you can compute HP. An giant supply of water so it dosn't overheat and boil. And a big wall between you and the dyno in case it blows the water brake. Guy I know damn near got killed when his dyno blew up.
my idea was to build a 3 point engine cradle with 2 points on one side of the engine being bearings and a third point on the other side sitting on a loadcell, to do the calibration i was thinking of using a large torque wrench i know they go over 1000 ft lbs as i have seen them in truck garages, i`make an atachment point to the engine at the crank centerline for the torque wrench. but the load part still has me thinking, i have been involved with truck and tractor pulls and they use water for the tractor dynos i know.
the math is very simple, really....the only thing you have to do is figure out how many feet long the torque arm is, and multiply the scale reading by that lenght to get foot pounds. hp = rpm x torque / 5252, and you're done
Or do it electrically. hook the engine to a big generator, attach the generator to a big variable load, like a diesel electric locomotive heat sink, then just measure the output in watts.
that thing is crazy its a camaro! and its in utah! i wonder if it near me and how much he'll charge? I want a dyno for my briggs and stratton motors.
Here's a page with some info and links on it. It's pretty old, so a lot of the external links are dead. http://pages.quicksilver.net.nz/geoffm/dyno/dyno.htm
I realize this an old thread, but are there any new Ideas four years later? I was thinking maybe a big torque wrench(I've used ones with 1000+ ft.lbs capacity) on a torque converter? I think it'd work until the tq converter locked up, but if someone used one with a higher stall than the engine's redline(or higher than you'd be testing it at) would it work? I've only messed with manual ******s, so my knowledge on converters is limited, but as far as I can see it should work? the tq wrench would have to be the lever type, not the click type
It wouldn't be practical on a BBC or some 500HP monster, I'd limit it to little 4 bangers and old (200- or less HP engines) once you got the tq numbers you could find your RPM's and figure your HP...
I don't see spending a couple thousand(that some don't have) to play with in the garage. I think budd, and others like him(and I) are just looking for a little dyno to play with in the shop. I'd like to see how some of the old motors I rebuild compare to the stock ratings, How different carbs compare, timing differences, and other stuff that we do on the little flatheads and sixes in our old trucks. It'd be more of something to play with and show off than something to get the maximum performance out of an engine. It's not like we're worried about squeezing that last 2HP out of our little flatty four banger...
I did build a small brake dyno back when I was racing Briggs and Continentals. I used a motorcycle front brake ***embly and a one foot arm off of that. And used a 50 lb fish scale for the torque reading. This was before load cells were affordable. You could scale up the whole operation and use a large truck or bus brake drum and hub. An Air brake chamber and foot pedal would make it really slick. Math is really simple. read the RPM, read the scale. write it down. go to the next rpm number you want and write those numbers down. The way you do it is go to the highest rpm and start braking, writing the numbers on the scale next to the rpm. I did 400 rpm increments. torque increases as you brake down the engine. when you cross the torque peak you need to start releasing the brake or the engine will stall. The useful number is the torque. HP can be easily calculated, but it's really not what you are looking for. If you have a ****s Encyclopedia, there are photos of really old brake dynos. Simple technology. That's where I started when I built mine. Frank
Why dont you just pay someone to dyno your engine...normal charge around 350 to 500...cheaper that way, and more accurate
I think this whole "hobby" is founded apon doing it yourself. If you have the knowledge and knowhow to build it and operate it safely, I say do it. Might cost you more to build it than to have someone else test it for you, but in the long run it would be cheaper. And even then, that's really not the point.
I built 2 dynos for kart racing over the years. I had used a Stuska water brake before and wanted something with a better control for smaller motors. I went with inertia style, flywheels. I used DataMite aquisition and software. Very reliable and accurate. The best part was that you could change the flywheel weight and change the HP range of the dyno without any calibration (once calculated MOI). When you get above a certain HP level, the flywheels become too big and going to a water brake makes more sense. I know that a well known road racer who lived nearby had his dyno brake tied to the pool. Once done testing, they had the pool up to temp. I have used ch***is and engine types on the race cars, each has a purpose, the question is really what your goal is. Where I live now, I have a built in dyno down the back canyon, 4 lanes wide and about 3 miles long. I just plug in the Pi Data recorder and wide band, then make a p***. The truck and trailer parked along the road looks just a little su****ious....
i always wanted to build one with a generator and a couple electrodes in barrels of water for the load....simple to covert watts or kva to hp. and torque
Just go to Don Garlits Museum in Ocala Fla. In the engine room part of the Museum is the orginal dynomometer that Smokey Eunick built in the earyly 50's. A**** other things is incorporates an old Fairbanks scale. It may be one of the earliest dyno's made.
Back before time began,i saw a homemade dyno that was a huge waterpump,normally used for irrigation, about 12-16 inch pipes,that had a restrictor valve,shot water up in the air at a calibrated telephone pole and a mechanical tach on the engine. Watch the waterjet,close the valve some and check the rpm. A chart then was consulted and it worked out. This was about 50 years ago and the shop broke industrial engines in running the pump. Dumpy shop in central florida.
The generator idea sounds like fun, but it will have to be a big generator. Maybe a dozen alternators hooked up in parallel? Let's see 50 amps from an alternator, times six alternators is 300 amps times 400 volts, about the maximum the alternators insulation can take, =120 KW or approx 150 Hp. E=IR so 1 and 1/3 ohm resistance total, but loading each separately would be safer if one fails, and then read the amperage from the ground side; so six at eight ohms each. copper water pipe conductors maybe? Manually controlled fields to set the load, a MAF sensor etc. Could be a lot of fun if you built it in your' spare time and weren't worried about the accuracy.
Mount a tach right next to the torque wrench scale, and video tape it on a pull. If you want to do it the traditional way use an 8mm camera.
i have been thinking about checking out the brakes off an offroad logging truck, they have a system to spray water on them so they don't get too hot, to calibtate my setup i was think of useing a 1000 ft lb torque wrench.
There was an old popular mechanics article I saw online on how to make your own water brake. It could only absorb about 30hp, but was designed so you could stack them to whatever HP range you needed. Not a problem when a hot banger was barely touching 100hp but would get large quick with something as simple as a mild SBC.
i have seen water dyno's used at tractor pulls where they are hooked to the PTO, they have a garden hose hooked up and a guy stands there truning a bil wheel.
I made one once with a 1 ton truck disc front brake. The rotor was connected to a top loader 3spd transmission left in low gear (~ 3:1 ratio) and the other to the rotor via a home made drive shaft coupling. The spindle with caliper were mounted to the frame and allowed to pivot. I made a torque arm out of steel 3 feet long from center of pivot to where it connected to a 250# hanging scale suspended from the rear of the frame. I made a control panel with a radiator and Morse throttle controls, tach and instruments on casters where I could roll it to the front of the engine and hook the radiator hoses and put a box fan inside of it between the radiator and control panel. I mounted a large master cylinder to a angle iron frame with a seat on top where I could sit and stand on a pedal to load the engine against the brake while I tried to watch the tach and scale (X the 3 ft). had to cool with water hose often, and the speed of the spinning rotor, even at 3:1 used to keep me on edge. If I could get those 2 numbers, I could get a HP guestimate and see power trends with cams manifolds headers etc... I used to have some pics. HP = Torque X RPM / 5252 (a constant) I heard of another once using a variable pitch 3 blade aircraft prop, but never saw it. Sounded practical. Tom S. in Tn.
http://velobanjogent.blogspot.com/2011/07/dynomometers-and-engine-testinga-brief.html Good info here.
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