Beyond my skill level!

Found this yesterday at a car boot for £1, I cannot belive how ell made it is.

Some sort of differential for something. Largest gear is 56mm diameter.

Turns like silk with just one tiny rough spot.

Is it for anything in particular?

Cheers, Martin

Hi , no idea for what it's used in but bet it wern't cheap to make......

Clogs

Very odd, I can't think what would want a diff with different spur gears on either side.

Think 'mechanical analogue computer'. Maybe??

Special purpose, like the WW2 electro-mechanical bomb sight.

A differential can function as an adder (or subtractor) and the different size spur gears achieve different scalings of the respective variables.

Best regards,

Swarf, Mostly!

A bit like that differential drive for a gear hobber somebody posted a week or two ago

It's funny to think that most cars in the coming years won't have a differential as we switch to electric vehicles.

How does that work?

I can see individual motors on each side, but how does that split the torque like a diff?

Fancy electronics with current/speed sensors I'd hazard.

I'm a bit sketchy on the differential effect when using separate motors on either side with the motors in series, but as the inside motor on a turn is slowed down the outside motor gets more electrical "bits" and speeds up. I know this from practical experience but don't understand how it works.

Edited By norman valentine on 27/02/2017 20:42:58

• Norman, the mechanical diff feeds power to the wheel that is slipping. Hence the 'limited slip diff' in sports cars, which avoids this. Electric motors in each drive wheel don't do that, as a DC electric motor draws most current, developing most power at maximum load, ie the wheel that is NOT slipping. This has been the case ever since electric cars existed, about 100 years ago and more. This is also why DC motors are so good for traction purposes, and also why maximum cooling air is required when starting, since the motor is turning slowly, yet drawing maximum current, and getting hot. Hence particularly the air blower noise on Eurostar trains and other such railways.

Geoff

I thought the traction motors were AC or are you referring to motors for fan cooling?

Steve

I haven't a clue what it is from but the large gear wheel on the left appears to be friction welded onto its shaft. This would suggest that it is a relatively recent mass produced item.

What is the finned thing on the right of the assembly? Another photograph would be useful.

JA

SDL, I was referring to the cooling fan blowers. I am not familiar with the torque characteristics of AC motors, but the same basic principles no doubt apply. From rest, the motors are drawing current but turning only slowly, so they need help to stop them overheating.

Geoff

I have just realised it is a gear wheel bolted onto a disc. Strange.

JA