planning to get a 8880 Supercar... gearbox question

[jaumeBCN]

yep, I am planning to get this beauty, my question is, what happens if the gearbox is put in the middle (neutral) position? The v8 motor is unlinked to the wheels?(like a real car) On my late childhood fantasized about swapping that V8 for the 9v motor of that era, and from youtube I am doubting if doing that is even possible (many arging about that 9v motor not having any torque), well I suppose for it to be just your average Mabuchi branded deal, present on all toys, and capable of anything with enought reduction gear. I'l let it here because I'm drifting...

[allanp]

Yes, when in neutral the wheels and engine are disconnected like a real car. As for the ungeared 9v motor of that era, as it is it does have very little torque but that's not the same as saying it has very little power output. It has almost the same power output as a PF M-motor. You just have to gear it down. An ungeared 9V motor that is subsequently geared down to the same speed as an M-motor will give you about the same torque as an M-motor. However, when motorising 8880 there are other things to consider. The gearbox in particular was never designed to take the load of actually moving the car, only the fake engine. The drive train of the car also has a lot of friction in the wheel hubs. Most of the motors power will be needed just to overcome that.

Edited July 16, 2014 by allanp

[jaumeBCN]

Thanks, I did fear that... such thin axles for that mountain of a car...

[allanp]

The cars size and weight isn't really the problem. The old 9v motor would have no problem moving that if geared down properly. The problem is the huge amount of friction in the drive train which wastes most of the motors power. The axles are up to it, but the gears are not, particularly the old 14t bevel gears and also the universal joints. One option is to swap the hubs with the new ones from 42000 race car and the bevel gears with newer ones. You may also need to redesign the 4 speed gearbox to handle more torque, like this one.

It would be great to see you implement these changes without significantly altering the looks of the car. I don't think it would be that hard.

[jaumeBCN]

The cars size and weight isn't really the problem. The old 9v motor would have no problem moving that if geared down properly. The problem is the huge amount of friction in the drive train which wastes most of the motors power. The axles are up to it, but the gears are not, particularly the old 14t bevel gears and also the universal joints. One option is to swap the hubs with the new ones from 42000 race car and the bevel gears with newer ones. You may also need to redesign the 4 speed gearbox to handle more torque, like this one.

It would be great to see you implement these changes without significantly altering the looks of the car. I don't think it would be that hard.

Was going to comment about this, did seen that LEGO gearbox is just a 2 speed deal, so in the 8880 it's two gearboxes, the second one set as an overdrive, because of this, the direct is actually the second speed, being the 3rd and 4th overdrives... I planned of reversing the overdrive gears so they act as a low gear (dunno the English name) and place it on 1st/2nd section of gearbox. Also found that the simulated v8 is placed behind a chain (bad idea to put torque there) so actually I plan on putting the 9v motor after the chain, on the primary gearbox axle (edited post to include proper mechanic terms, sorry if you'd get lost) sadly I fear I must get the set to fully understand how it works.

Besides. ¿It's legal to lube LEGO? I understand lots of parts could use some of the stuff (Ceramic grease because it doesn't attack plastic)