David Jenkins
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| posted on 29/6/04 at 07:58 AM |
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Want to run fast, going nowhere...
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]
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theconrodkid
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| posted on 29/6/04 at 08:22 AM |
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yup liftimg 1 wheel will do it,safer to use axle stands tho
who cares who wins
pass the pork pies
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Deckman001
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| posted on 29/6/04 at 08:48 AM |
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That and point the car towards a bit of open road,, just in case !!
Jason
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spunky
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| posted on 29/6/04 at 08:56 AM |
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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
The reckless man may not live as long......
But the cautious man does not live at all.....
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David Jenkins
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| posted on 29/6/04 at 09:34 AM |
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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
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andyps
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| posted on 29/6/04 at 12:17 PM |
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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.
Andy
An expert is someone who knows more and more about less and less
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Alan_Thomas
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| posted on 29/6/04 at 02:57 PM |
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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!
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David Jenkins
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| posted on 29/6/04 at 03:05 PM |
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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
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Alan B
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| posted on 29/6/04 at 03:12 PM |
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quote:
Originally posted by David Jenkins ......I reckon that a running car has at least as much torque!
David
And the rest.........
A small lathe might only have a 3/4HP motor (@1450 rpm)......
Scary......
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Dick Axtell
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| posted on 29/6/04 at 07:30 PM |
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Gearing?
quote:
Originally posted by Alan B
A small lathe might only have a 3/4HP motor (@1450 rpm)......
Scary......
But significantly lower gearing, and t'fore greater torque, nicht war?
Work-in-Progress: Changed to Zetec + T9. Still trying!!
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Alan B
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| posted on 29/6/04 at 08:33 PM |
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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]
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dblissett
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| posted on 29/6/04 at 09:24 PM |
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torque
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
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Alan B
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| posted on 29/6/04 at 09:29 PM |
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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...
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David Jenkins
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| posted on 30/6/04 at 07:12 AM |
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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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NS Dev
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| posted on 30/6/04 at 07:46 AM |
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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"
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Alan B
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| posted on 30/6/04 at 01:30 PM |
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quote:
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
Yep...you gotta be very careful what you say when there are nerds and engineers at large....
Anything is fair game....LOL
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dblissett
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| posted on 30/6/04 at 06:07 PM |
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golden rule
this is from my old mentor
dont put your fingers
were you would'nt put your dick
enough said
dave
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NS Dev
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| posted on 30/6/04 at 06:29 PM |
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I love those old mentor's rules, and every one is true as well!!! Had to laugh out loud when I read that one!!!
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Alan B
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| posted on 30/6/04 at 06:31 PM |
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quote:
Originally posted by dblissett
this is from my old mentor
dont put your fingers
were you would'nt put your dick
enough said
dave
Oh........now you tell me....
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Peteff
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| posted on 30/6/04 at 08:43 PM |
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You don't bite your fingernails then!!!
I wouldn't dream of putting my fingers in Christina Aguilera's mouth, but.......
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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Metal Hippy
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| posted on 30/6/04 at 08:48 PM |
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"You dirty old man..."
Cock off or cock on. You choose.
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andyps
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| posted on 30/6/04 at 08:54 PM |
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quote:
Originally posted by Peteff
I wouldn't dream of putting my fingers in Christina Aguilera's mouth, but.......
Surely that would be OK as foreplay
Andy
An expert is someone who knows more and more about less and less
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pbura
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| posted on 1/7/04 at 03:49 AM |
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quote:
Originally posted by Peteff
I wouldn't dream of putting my fingers in Christina Aguilera's mouth, but.......
Should be OK as long as you don't have any open cuts.
Pete
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NS Dev
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| posted on 1/7/04 at 06:56 AM |
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tee hee!!!
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