An idea is to have a pump that pumps fast and at lower pressure drive a hydraulic motor slower and at higher pressure. It should make relatively little noise and be able to provide a lot of motor speed reduction, with the bonus of supplying slip during overload. Would it be a possible way to get big "down-gearing" in a single reduction stage on an ebike?
Hydraulic rpm reduction
- Thread starter DDrm
- Start date
ZeroEm
1 MW
You mean bypassing? Unless you use a torque converter.
Hillhater
100 TW
Hydraulic pumps and motors = = major efficiency loss .
Hillhater
100 TW
?? How exactly does the pressure increase between the pump and the motor ?DDrm said:
Hillhater
100 TW
But why would you choose a high rpm motor for a low rpm application ?DDrm said:
This is why units like “HUB” motors are used...no gearing, belts or chains..direct , low rpm drive with high efficiency and minimal losses.
Hydraulic systems have their uses, but usually that is for low speed, high torque applications with high power motors where a 10+% efficiency loss is acceptable.
ZeroEm
1 MW
No!
Ever work around water systems that run and pressure up a system. It's not the fluid that compresses. They have a tank with a bladder that has a air pocket that compresses. Think about hydraulic brakes? when the peddle gets spongey it air in the lines.
DogDipstick
100 kW
ZeroEm said:
Yeah .. "Under pressure " is not the same as "compressed"
Hillhater
100 TW
The system cannot “increase pressure” without the addition of more energy, and the only energy source in this “pump + motor” system is the pump !DDrm said:
If the motor “consumes more volume per revolution” .that is just a speed change, not a pressure increase, which simply means that the motor runs slower than the pump, and by definition, the pressure MUST REDUCE across the motor , for the motor to work.
Hillhater
100 TW
And a hydraulic system with an electric motor, pump and hydraulic motor,....would be so much lighter in comparison ??DDrm said:
Hillhater said:
The pump has the electric motor, and then there is an output motor that uses the liquid from the pump, but is mechanical.
Well, thanks for your input. I appreciate it. I mainly just wanted to put the idea out there, but don't know details about whether it would work or not. So far consensus says it's not feasible.
Hillhater
100 TW
No, it is feasible, just not practical or realistic for an Ebike of even a small EV.DDrm said:
It would be complex, expensive, heavy and inefficient,....compared to simple chain / gear reduction
markz
100 TW
Practicality is necessary sometimes
https://go.discovery.com/tv-shows/diesel-brothers/videos/one-beefed-up-diesel-motorcycle
Here is a read up on hydraulic motor for transportation.
https://www.womackmachine.com/engineering-toolbox/data-sheets/vehicle-drive-with-hydraulic-motors-part-1/
https://go.discovery.com/tv-shows/diesel-brothers/videos/one-beefed-up-diesel-motorcycle
Here is a read up on hydraulic motor for transportation.
https://www.womackmachine.com/engineering-toolbox/data-sheets/vehicle-drive-with-hydraulic-motors-part-1/
ZeroEm
1 MW
Not to discount hydraulics. It's great is you have a main drive motor and mount a pump to do just about everything you can imagine but it requires cylinders, hoses, seals, lines and all of this is heavy. Have always been interested in mini hydraulics. The new electric motors and batteries have taken it's place. I'm sure there are still applications where it would shine. I know you can get a lot of power from hydraulics. Lift houses, move anything you can think of. Not sure speed and power saving is a goal.
AussieRider
1 kW
G'day DDrm.
Look up the Honda DN1 motorcycle. It had a hydraulic CVT that used a variable displacement pump. Low volume for high torque ie: low gear & high volume for high gear. Clever, but complicated, weighed a ton & performed like a slug.
AussieRider
Look up the Honda DN1 motorcycle. It had a hydraulic CVT that used a variable displacement pump. Low volume for high torque ie: low gear & high volume for high gear. Clever, but complicated, weighed a ton & performed like a slug.
AussieRider
Yeah, lighter and also very likely more efficient too.
If you want the highest power to weight ratio in any motor, you should consider a CYC Pro X1 mid drive.. as far as hub motors go, it's a tie between the Bafang G310 and the MAC these days, as far as i know.
If you want the highest power to weight ratio in any motor, you should consider a CYC Pro X1 mid drive.. as far as hub motors go, it's a tie between the Bafang G310 and the MAC these days, as far as i know.
