h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Entry: Differentials - A687017
Author: Just zis Guy, you know? [my other car is a bicycle!] - U54363

I can make differentials out of lego. It's quite instructive.

You really are trying to strecth people's visualisation skills, aren't you?.
I have enough trouble trying to visualise how a motorbike clutch works, even after taking one to pieces. Somehow, once I get more than one fixed and one rotating assembly, my mind starts to fuzz over. I'll give it a read tomorrow, and see if I can get my head round it.

Strecth? Too much

Excellent entry. I was able to follow and understand this, although I did have to read a couple of paragraphs two or three time to get my head round it, and draw a sketch to help me visulize it. spotted a few typo's towards the end.

"Spinning noe wheel like this will subject the diff to stresses"
should be
"Spinning one wheel like this will subject the diff to stresses"

" so there have to be differentials on both"
should be
" so there has to be differentials on both"

"you get some traction on the wheels whaich are not spinning"
should be
"you get some traction on the wheels which are not spinning"

BTW also enjoyed your entry on gerboxes, and I'm looking forward to reading your entry on CV joints. (you could makes these into a university project)

SK

Some old cars had two independent hand brakes, especially if they were raced in muddy terrain. If one wheel was spinning in the mud the driver would fiddle with the brake on that side only and the other wheel would hopefully drive you out. (I think they were called fiddle brakes?)

I knew instantly when I saw he title that this was about autombile back axles. That was because I had read about gearboxes hours before. (And 'cos I'm concerned about the slop in mine in the Morgan.)

But maybe you could qualify it? Someone might think it's a branch of mathematics?

Just a thought

Awu.

Perhaps retitling it as "Differentials: clever gears for going around corners" will get over the confusion with "Differentials: those tiny little things in Mathematics".

You should limit your use of the word "Now" in the detailed explanation of the differential. It feels like each section starts with "Now...".

There are some typos:

diff - should be spelled out in full as differential
noe --> one
whaich --> which
spininng --> spinning
one the outside --> on the outside

Some updates.

I see you managed to sneak in a whole load of new stuff at the end of the Entry!

I don't understand what you mean about rear-wheel drive cars having solid axles with diffs in them. In what way are the axles solid?

Why do the conical gears in the diff not have proper bearings?

And I certainly don't understand the comment about minis at the end.

Hi JZG,

Only thing I didn't follow about this first time was which way the crown wheel faces. I think you should mention it's parallel to the wheels. Otherwise it gets real confusing with those conical gears trying to rotate through the axle!

Sir Kitt - I think your second correction is wrong. (Can't view it while I'm in Post, but I think it was "... conical gears [plural] ... have ..."

(to JZG again) For the record, I liked your article on constant velocity joints, too. Seems to have disappeared from PR, so I guess it's been accepted for editing. Well done.

Gif

"have to be differentials on both" or "has to be a differential on each" are both correct.

Should plan my posts more carefully!

Gif

Fair point, yes must be parallel to the wheels. Will fix.

Hi!

I've just finished editing this entry (A692958). It was pretty solid, so the only changes I've made have really been tweaks dictated by the House Style (see <./>Subeditors-style</.&gt

If you have any queries, or spot any problems with it, please let me know!

Frankie Roberto

Hi, thanks. Couple of things I missed: first there should be a link to the entry on The Italian Job - http://www.bbc.co.uk/dna/h2g2/alabaster/A500509.

Second, para 2 reads a bit oddly on reflection.

Now: "And that width means, of course, that the wheels one the outside of the bend have further to go than the wheels on the inside - which is fine for whichever wheels are not being driven, they can be like supermarket trolley wheels and go as different speeds (though hopefully not different directions as supermarket trolley wheels generally do), but the driven wheels are a different matter. You have to drive both of them, but let them turn at different speeds."

Suggested tweak: "And that means, of course, that the wheels on the outside of the bend have further to go than those on the inside - which is fine for whichever wheels are not being driven, they can be like a supermarket trolley's castors and go at different speeds (though hopefully not different directions as supermarket trolley castors generally do), but the driven wheels are a different matter. You have to drive both of them simultaneously, while letting them turn at different speeds."

How would that be?

That sounds fine. I've e-mailed the changes to Anna, you should see them come up soon...

Frankie

Loved the entry- but I had problems imagining it, could you link to a site with a picture, or even a photo of one of you're lego models.

Understand if you can't find one tho.

Hi there,

I've made those changes - should be all right now

Anna

Ta. Pity we can't have pictures.

If you're lucky, the in-house artist will design a picture for the entry...

Not sure how she would get on with yours though...