Hi,

Many eddy brakes have their highest torque at low RPMs, like around 800-1000RPM. They will still have a decent torque at 540 RPM. 

But of course that low RPM means the HP will be low, unless you have very high torque capabilities. For 250HP at 540 RPM you need about 3300 Nm, which means a bad ass (=expensive) retarder. 

You should consider gearing it up.

Ok, I thought so too. so I just have to add simple transmissions. eg with 3HB V-belts or wide toothed belt, such will be the quietest with a ratio of 2: 1 or even 3: 1, in the same power, torque will be lower.

How can I easily read the engine's speed? alternator, injectors or just knowing the transmission ratio from the pto shaft 

Yes, heavy duty toothed belts should work fine.

You need a trigger wheel at the retarder, see  https://yourdyno.com/rpm-sensors/. Since your gear ratio is fixed, you just key it in and you will get Engine RPM from YourDyno.

I would consider a 10" Ford Complete Strange Engineering  differential centre section with a full spool 40 spline axle combination  with what ever ratio you want to spin the selected 3000rpm retarder with correct holding torque.

Strange Engineering centres and axles can handle big horsepower/torque.

There are other great differential USA manufacturers that supply great products too to the racing industry.

The differential is based on a ford 9inch differential  the operation will be more smoother and less noisy than a gilmer belt drive.

With the differential setup it positions the retarder rotation parrallel with the test tractor. So so form of bullet proof protection cover would need to be implemented .

I use yourdyno for tractor testing - and can recommend it  😀 

Most tractors (i would say all) have the ability to switch between 540 PTO rpm (at 2000 engine rpm) to 1000 PTO rpm (at 2000 engine). But it might be different models you have in poland.

Just checked datasheet from my frenelsa retarder. It has highest torque rating at 650rpm. 

thanks, yes I know that there are turnovers and 1000 in almost every tractor, many also have 750rpm.

dear friend MadsWP if you can send some photos of your tractor dyno on email adagro24@gmail.com. The brake that I take into account is Telma cc200 or cc250, which is the most popularon the aftermarket.

As for the gearbox, it seems to me that gearbox with teeth and oil, often it is 80w90 will generate unnecessary resistance.

Although the old dyno Froment with which when I was working had just such mechanical transmission, from which two shafts came out one to connect 540 and the other direct to 1000, but there was a generator and not Telma.

Frenelsa brake I did not see in the advertisements

My brake is disassembled at workshop right now due to upgrading. I can send pictures within a week or so. Its an old EGGERS PT160SE fully upgraded. basically only the trailer thats stock. 

Remember that belts do also make friction.

Here you see a picture of dyno and a test of a john deere tractor.

dyno

 I Ok i weld everything and on next week i start test and i also have two questions 

 Im realy exciting i have Klam cfk 500, 3850 Nm in 1000rpm,  

the load cell is 1000kg and the largest mass for calibration is a barrel of oil 200 liters 196 kg gross I wonder how to hang, is 30kg enough?

1. Do I have to mount a mass for balance on the opposite side to the load cell?  I don't see it in any pictures 

2. does anyone have a mobile dyno and uses load cell locks for transport? Why im asking? Example airconditioning  station have locks under load cell under gas tank for transport 🙂

3. does it need any frame over the load cell? happens that it can break?

Ok 4 questions 🙂

Hi,

1. No, zero cal takes care of that
2. Some dynos have this. I once spent quite some time remote debugging with a customer when we eventually found the transport bracket was on ;-). I don't think it is necessary for most setups though. If it can get big impacts somehow during transport, then add this.
3. Yes, if it is used in stretch mode. Most cells are used in compress mode, which makes it unnecessary 

In terms of load cell weight:

• Go for minimum 10% of the rated capacity. There is no magic number, but any error in linearity would amplify, so higher is better. 
• It is possible to add a long arm and place a smaller weight far from the center. You need to work out the effect on the load cell by calculations (think in terms torque (arm and weight)). In this case, add an arm that is symmetrical around the brake center, otherwise you need to work out the effect of the weight of the arm too.