I'm currently having trouble getting my speedo to work (my own fault for being a smart-arse who made his own gearbox speedo sender ). I need to do some diagnosis and trial-and-error to get it fixed - but to do that I must generate speed signals, i.e. the back wheels have to be turning.

Am I right in thinking that lifting only one back wheel will allow me to pretend to be moving? I only have a normal Escort diff at the back (not LSD). Jacking 1 wheel up would be a lot easier that trying to get the whole of the back of the car up onto stands (always seems a bit wobbly to me, and a high risk of damage). I'm not talking about high wheel speed - just the equivalent of 10 - 15 mph would be enought to diagnose my problems.

cheers,

David

[Edited on 29/6/04 by David Jenkins]

yup liftimg 1 wheel will do it,safer to use axle stands tho

That and point the car towards a bit of open road,, just in case !!

Jason

I posted on the same problem a while back. The lifted wheel will turn at double the speed for given engine speed. To avoid confsion I lifted them both.

John

Cheers folks,

I don't care what speed the wheel spins at - my sender is on the gearbox speedo cable outlet.

I had tried putting the back end up on 2 stands - it just felt a bit dodgy. Also, it started to rain and it took me 3 or 4 minutes to get the car back off the stands and back in the garage!

It would only take 30 seconds to hoist 1 side at the back - all I want to see is a response from the speedo when I try various diagnostics...

rgds,
David

I always raise both sides - surely much safer. Make sure you put a good block in front of the front wheels just in case anything slips.

Use an axle stand to just lift one wheel. Its my standard technique for polishing the alloy rims, bit of choke 1st gear then the wheel is running slowly for a bit of power polishing!

You know - the thought of that scares the hell out of me! There's at least one person here who'll tell you about getting fingers caught in a lathe, and I reckon that a running car has at least as much torque!



David

quote:

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Originally posted by David Jenkins ......I reckon that a running car has at least as much torque!



David

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quote:

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Originally posted by Alan B
A small lathe might only have a 3/4HP motor (@1450 rpm)......
Scary......

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Dick, I wouldn't say significantly lower gearing........I'd say that the car wheel in first gear would generate a LOT more torque than a small lathe....IMO

Anyone care to run some rough figures?

[Edited on 29/6/04 by Alan B]

calc for torque is (nm)


kw x 9545 dived by rpm

and a car engine has a hell of a lot more torque is first so dont try it
cheers dave

Ok..I will...

3/4 HP @ 1450 rpm has about 2.7 ft pounds of torque...geared down to say 100rpm is about 39 ft pounds of torque..

Small 4 cyl. engine....say 20HP @ 1000 rpm (wild guess).......105 ft pounds torque...geared down 10:1 (low gear x axle ratio) gives 1050 ft pounds torque......

Massively more unless my figures are way out or my logic or formulas are wrong.....

No doubt someone will correct me...

Must remember to make it a bit more obvious when I'm writing something 'tongue-in-cheek'... . I have this habit of writing or saying flippant things that people take seriously...

I still reckon that I wouldn't put my fingers near the rotating parts of my 1HP lathe, let alone the rotating wheel of my 100BHP car...

rgds,

David

I also would't run my car for very long at all with one wheel on the ground and one off it, the diff is not (usually) designed for this and can be damaged, or worse, and very unlikely, could seize and jump the car off the stands. Just make up a couple of really sturdy and stable stands, or tack weld your pair of axle stands to some scrap 1/4" steel sheet or the like to make them a bit less "wobbly"

quote:

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Originally posted by David Jenkins
Must remember to make it a bit more obvious when I'm writing something 'tongue-in-cheek'... . I have this habit of writing or saying flippant things that people take seriously...

I still reckon that I wouldn't put my fingers near the rotating parts of my 1HP lathe, let alone the rotating wheel of my 100BHP car...

rgds,

David

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this is from my old mentor

dont put your fingers
were you would'nt put your dick
enough said
dave

I love those old mentor's rules, and every one is true as well!!! Had to laugh out loud when I read that one!!!

quote:

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Originally posted by dblissett
this is from my old mentor

dont put your fingers
were you would'nt put your dick
enough said
dave

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I wouldn't dream of putting my fingers in Christina Aguilera's mouth, but.......

"You dirty old man..."

quote:

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Originally posted by Peteff
I wouldn't dream of putting my fingers in Christina Aguilera's mouth, but.......

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quote:

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Originally posted by Peteff
I wouldn't dream of putting my fingers in Christina Aguilera's mouth, but.......

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tee hee!!!