Q&A Forum
I'm new to the whole Dyno thing..I have a older water brake Dyno that has been updated with yourdyno software that I have some questions about...
Does a water brake have to be at a certain Rpm or MPH to work?
This dyno water originally designed to have a garden hose ran to it and was converted by previous owner to a self contained unit with a 70psi pump..Does the brake need to be able to gravity drain?
My problem is the brake doesn't really seem to hold..it is small Dyno designed for motorcycles and ATVs up to 200hp...thank for any information or opinions!
Hi,
A water brake has very low braking capacity at very low RPMs. Look here for some example torque curves.
In addition to the RPM, the brake force is dependent on the fill level. The more full of water it is, the more it brakes. The brake torque does not depend on the flow through the brake, flow is just necessary for heat dissipation purposes (and to reduce braking force the water need to exit relatively quickly). If you want to know if your brake can hold your torque, just close the output valve (almost), and open the input valve completely, ensuring the chambers are full. Then give it a go at full throttle. The engine should not be able to go through its rev range. Ideally it should top out pretty early.
If you engine has very low torque at low RPM, you may need to open the inlet value when RPM has increased somewhat to do the test.
Note that some setups run two valves; one on the inlet and one on the outlet, and they run opposite of each other (if one close the other opens).
Note that some setups run two valves; one on the inlet and one on the outlet, and they run opposite of each other (if one close the other opens).
This one has 2 electric valves ran off a push button...when running a low tourqe bike say around 15ft lbs andand tha only geared to do about 50mph in 6th gear wide open the brake really has very little effect on it...could it be that the bike tire/ gearing combination is not turning the brake enough rpm to work correctly? To my understanding this brake should be able to put enough load on this motor to shut it down? Is that correct?
Roughly what RPM does the brake have at full engine RPM?
Roughly what RPM does the brake have at full engine RPM?
I'm unsure what your asking...the motors turn about 12,500rpm...the brake will only pull the motor down to about 8000rpm but thats in 6th gear WOT...
So when the engine is at 8000 RPM, what is the brake RPM?
So when the engine is at 8000 RPM, what is the brake RPM?
Pretty low only like 1000 to 1200 is what it reads..
So that's probably the issue, the brake does not have enough torque holding capacity at that low RPM. Any way to gear it up?
So that's probably the issue, the brake does not have enough torque holding capacity at that low RPM. Any way to gear it up?
It's connected right to the drum/roller...so not with out adding a jack shaft and a couple sprockets..bike I'm running on it only has a 15" tire so I could always step up to a 18" tall tire if that would help....the Dyno is a older patraco as far as I know this is how it's always been set up...what kind of Rpm do I need to see out of it you think? I will say this was originally a water brake Dyno that was designed to run off a garden hose and the dump solenoid just went to drain...the previous owner converted it to a self contained unit that's fed off a tank that feeds a pump that feeds the brake and the dump solenoid dumps back to tank...here is a diagram I made up of how it setup... please let me know if the way it's set up is a issue...
1000 RPM is low for many water brakes.
If you are sure you water brake fill level is max and still cannot hold the torque, the only option is to increase the brake RPM. Water brakes can generally accept and work very well at very high RPMs.