Configuring a new chair (essential!!!)

[Michalych1974]

That tire pressure is certainly high enough - is that the pressure in both the front and rear tires? Do front and rear tires have the same or different diameters?

Is the backward speed programmed lower than forward?

The diameter is different. 36 cm in front, 32 cm in the back. The drive is front-wheel drive.The speed back is less.

[LROBBINS]

Now having more difficulty going backwards makes sense.

[Michalych1974]

https://www.meyra.com/wheelchairs/productetails/product-47/

Servo rear steered single channel motor controller based on a special single channel parallel connected drive channel r-net power module. Large group 27 battery (heavy). High speed motors, low torque garanteed! On slower versions they just program for lower speed and keep the same gearing. So still low torque. Lots of mass at both ends. Basically a servo steered scooter. Actually low tyre pressures help on curbs.

https://youtu.be/tfuFF40MwM0?si=Su2911giPTwSfPMp&t=937 The same wheelchair - there is enough power, the wheels are slipping.

[Burgerman]

The only way a wet tyre is going to get enough traction for the curb or the mud is if you had 4 wheel drive.

[Michalych1974]

The only way a wet tyre is going to get enough traction for the curb or the mud is if you had 4 wheel drive.

The torque of the motor is 9 550 × 0.7 / 4,100 = 1.63048780488 Nm. (Power 700W number of rpm 4100)
the reduction in the gearbox is 16.9 times.

Therefore: the torque on the wheel is greater than on the shaft of the electric motor.


Or is that not enough? (provided that the electric motor is in good condition)

[LROBBINS]

That is the torque at maximum efficiency. The torque produced at lower speed/higher load can be much, much larger.

[Burgerman]

What lenny is telling you is that the 700 watt figure is practically meaningless. Ignore it. The motor has the power to rotate the wheel. But there is no tyre/road grip or traction. 2 wheel drive wont work.

[Michalych1974]

What lenny is telling you is that the 700 watt figure is practically meaningless. Ignore it. The motor has the power to rotate the wheel. But there is no tyre/road grip or traction. 2 wheel drive wont work.

Based on my calculations, the torque on the engine shaft should be: 9550x0.7/4100 = 1.63 Nm (engine power 0.7 kW, engine speed 4100 rpm)
Next, I have a differential gearbox with a decrease of 16.9 times, therefore, the torque will increase by 16.9 times.
1.63 × 16.9 = 27.547 Nm, are we removing 10% of friction losses? IS THAT ENOUGH? 25 Nm = 2.5 kg on a 1 meter long lever, the motor must rotate the wheel.
Did I calculate everything correctly?

[Michalych1974]

What lenny is telling you is that the 700 watt figure is practically meaningless. Ignore it. The motor has the power to rotate the wheel. But there is no tyre/road grip or traction. 2 wheel drive wont work.

Based on my calculations, the torque on the engine shaft should be: 9550x0.7/4100 = 1.63 Nm (engine power 0.7 kW, engine speed 4100 rpm)
Next, I have a differential gearbox with a decrease of 16.9 times, therefore, the torque will increase by 16.9 times.
1.63 × 16.9 = 27.547 Nm, are we removing 10% of friction losses? IS THAT ENOUGH? 25 Nm = 2.5 kg on a 1 meter long lever, the motor must rotate the wheel.
Did I calculate everything correctly?

[Burgerman]

No.
The 700 watts IS MEANINGLESS.

Why?
Because first you must multiply the maximum current the controller can give, around 200A? X the actual maximum voltage the conroller can provide = above 24V.

So you motor can take up to 200A x 24V = 4800 WATTS intermittently. And this is way more than the rated 700w continuous figure.
Add to this the fact that you do not know the efficiency at any given load/rpm which varies from a few% up to around 80% and you still cant know! And thats just motor losses. The gearbox loses more on top, and there are both constant rotating frictional losses that rise slowly / slightly with RPM and frictional losses that increase quite severely as load or torque increases.

And since the wheel is slipping anyway the max torque is already higher than the traction allows.

[Michalych1974]

No.
The 700 watts IS MEANINGLESS.

Why?
Because first you must multiply the maximum current the controller can give, around 200A? X the actual maximum voltage the conroller can provide = above 24V.

So you motor can take up to 200A x 24V = 4800 WATTS intermittently. And this is way more than the rated 700w continuous figure.
Add to this the fact that you do not know the efficiency at any given load/rpm which varies from a few% up to around 80% and you still cant know! And thats just motor losses. The gearbox loses more on top, and there are both constant rotating frictional losses that rise slowly / slightly with RPM and frictional losses that increase quite severely as load or torque increases.

And since the wheel is slipping anyway the max torque is already higher than the traction allows.

The wheel doesn't slip, it's not my wheelchair in the video.
Here is a graph of when the wheel cannot rotate.(1)
2 graph - when rotating 5 kg through a lever with a length of 60 cm

[Michalych1974]

No.
The 700 watts IS MEANINGLESS.

Why?
Because first you must multiply the maximum current the controller can give, around 200A? X the actual maximum voltage the conroller can provide = above 24V.

So you motor can take up to 200A x 24V = 4800 WATTS intermittently. And this is way more than the rated 700w continuous figure.
Add to this the fact that you do not know the efficiency at any given load/rpm which varies from a few% up to around 80% and you still cant know! And thats just motor losses. The gearbox loses more on top, and there are both constant rotating frictional losses that rise slowly / slightly with RPM and frictional losses that increase quite severely as load or torque increases.

And since the wheel is slipping anyway the max torque is already higher than the traction allows.

The wheel doesn't slip, it's not my wheelchair in the video.
Here is a graph of when the wheel cannot rotate.(1)
2 graph - when rotating 5 kg through a lever with a length of 60 cm

[Burgerman]

8X 176 = 1408 Watts as the data shows.
That will increase to around 24x 176A or around 4224 Watts as the motor speeds up. Since it requires ever higher volts to still pull max amps.

And as I said, the gearbox and motor efficiencies varies dratically from 10 to 80% approx depending on load. So you cant calculate it.

[Burgerman]

8V x 176A = 1408 Watts as the data shows.
That will increase to around 24V x 176A or around 4,224 Watts as the motor speeds up. Since it requires ever higher volts to still pull max amps. Forget your 700 watt figure!

And as I said, the gearbox and motor efficiencies varies dratically from 10% OR LESS AT STALL to 80% approx at light load depending on actual load. So you cant calculate it.

[Michalych1974]

8V x 176A = 1408 Watts as the data shows.
That will increase to around 24V x 176A or around 4,224 Watts as the motor speeds up. Since it requires ever higher volts to still pull max amps. Forget your 700 watt figure!

And as I said, the gearbox and motor efficiencies varies dratically from 10% OR LESS AT STALL to 80% approx at light load depending on actual load. So you cant calculate it.

is the wheelchair in good condition?

[Burgerman]

I have no idea. This tells us nothing about its condition. It is what it is. Looks normal and what you would expect. As stated earlier, you need lower gearing or more current capability or both. But that isnt what it is right now.