Gearbox Output Speeds

[SNIPE]

Hi

I am wondering, if this gearbox has 8 output speeds, it looks like some are slightly faster or slower than others but it could be down to me, or the motor slowing down. I dont have an XL motor yet and the batteries are not fully charged in my setup.

Note that I mean the speed (RPM) of the output shaft, not the ratio for the input to the output.

Go through the normal 4 positions but then combine them together to get another 4 speeds, so for example move one red selector up and the other one down.

Are there any unneeded gears here also?

LXF FILE

Regards,Snipe.

Edited October 15, 2014 by SNIPE

[dhc6twinotter]

Hard to tell for sure, but it looks like you have 4 speed total. It looks like you have the following gear combinations to your output:

1. 8/24

2. 12/20

3. 24/8 x 8/24

4. 24/8 x 12/20

Note that for number 3 above, your increasing the RPMs by a factor of 3, then decreasing it by a factor of 3. This means your output speed is the same as the input speed.

That should be correct, unless I'm looking at the pictures wrong.

Edited October 16, 2014 by dhc6twinotter

[SNIPE]

Did you combine one drive ring position with the other drive ring position? there is definetley more then 4 speeds,

Drive ring A moved up + drive ring B moved up

Drive ring A moved up + drive ring B moved down

Drive ring A moved down + drive ring B moved up

Drive ring A moved down + drive ring B moved down.

Yes theres the normal 4 positions too.

It also seems that the M motor works fine with this which is great, saved space there.

theres more gears in my final MOC but so far the motor isn't struggling in my earlier gearboxes

Edited October 16, 2014 by SNIPE

[dhc6twinotter]

If you replace the white clutch gear with a regular 24t gear, the whole system will bind up when two driving rings are engaged simultaneously. Since you are using a clutch gear, the system won't necessarily bind, but you are adding a lot of friction to the drivetrain.

Your gearing is setup for 4 different speeds, but If it looks like you are getting more than 4 speeds, it's because your clutch gear is working against your motor when both driving rings are engaged simultaneously, and the resistance is slowing down the output shaft.

[SNIPE]

What will the RPMs be for these speeds that use the white friction gear

[dhc6twinotter]

Not sure, but probably not a whole lot slower than the speeds that don't use the friction gear. I don't think you will be gaining an additional 4 speeds either, but looks more like 2.

Honestly, if you want to build an 8-speed gearbox, you will probably be better off using 4 driving rings. The design you posted above is intriguing, but the white gear is sapping power from the drivetrain. That being said, an 8-speed gearbox with two driving rings being engaged like you described above may theoretically be possible if you use a couple of differentials in there. Maybe.

Edited October 16, 2014 by dhc6twinotter

[SNIPE]

if there is definetley at least 2 extra speeds, that will do me, they have very low RPM's compared to the regular 4 speeds. I might just call them 'crawler gears' or is that for lorries ?,

The idea is for at least 6 speeds so it does not have to be 8, I wanted something small

So 6 speed is fine for the pickup truck. and might just fit in it.

Having 4 drive rings, given the area I have to fit the whole unit in is not doable sorry, However since this has a 24+8 then an 8+24 it reduces the train on the motor, I tested i with an L motor and it seemed to work fine.

I originally had neural as 1st gear so 1 drive ring was for 3 speeds but maybe its better to keep neutral even though the functions switcher gearbox does disengage the motor from 'drive' to something else such as 'winch' so it acts a bit like neutral there.

Edited October 16, 2014 by SNIPE