02GF74
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| posted on 27/2/07 at 12:02 PM |
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arrghhh so close .......
didn't get my MAC 
failed on speedo (bike). when on the rollers, the passenger side wheel was not turning which meant driver's side where the magnet/snesor were
mounted would not read correctly
almost didn't make the test - had to unplug the maplin's ignition amp and revert to condenser/points since engine was missing very badly
making it undriveable; even though I allowed plenty of time, that got me a bit panicky - especailly since there road works on my planned route so had
to take diversion that unfortunately did not take me back on to the original route so if you are going on A4146 from Hemel H to L. Buzzard - avoid
that road!
gonna splash out on greenguage speedo as have had enough mucking around - has anyone used the gearbox take off sensor?
good news is that brakes with the braided hoses are far better, my front wing stays survived and allegedly had it up to 81  if the bike speedo is to
be believed - get's a bit wobbly in crosswinds
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macnab
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| posted on 27/2/07 at 12:10 PM |
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what? are talking about an SVA test?
I don't get the speedo problem as many cars had it on one wheel only, like the beetle for example
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RazMan
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| posted on 27/2/07 at 12:12 PM |
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That's a pity, but surely if the rollers were working properly (or the car was repositioned so that both wheels were turning) it would have
passed.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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ayoungman
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| posted on 27/2/07 at 12:12 PM |
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A well done though is still to be deserved. If thats all that is needed, its a straight forward job to rectify.
"just like that !"
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02GF74
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| posted on 27/2/07 at 12:13 PM |
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yep retest yesteerday.
yes - since the rollers are 2 separate ones so will allow diff action.
I thnk one drum is dragging a bit more or else the diff is acting strangley - drives ok.
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daviep
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| posted on 27/2/07 at 12:23 PM |
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If the rollers are separate do they measure the speed of both rollers and take an average? or do they measure the speed of one roller only?
If it is the 2nd case moving your magnet to the other wheel would cure the problem.
Davie
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flange nut
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| posted on 27/2/07 at 01:23 PM |
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At what SVA station was your test?
Geoff
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02GF74
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| posted on 27/2/07 at 01:29 PM |
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I don't know how the rollers work; if they measure average, then I should ahve passed since one wheels is going at 2x andthe other is at 0.
During my lunchtime run, fitting an expensive speed taken off the gearbox won;t solve the rpoblem as again it will depend on how the rollers measure
speed; if I still have the same 1 wheel moving.one not.
SVA man said to take it to rolling road and get a print from that.
Don't understand why I am having this - I know the pass. side drum is tighter than drivers (may fit old shoes?) it does turn although not as
easily - I'm surprised that it produces the diff action.
re: centre, Leighton Buzzard
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02GF74
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| posted on 27/2/07 at 01:31 PM |
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quote:
Originally posted by daviep
If the rollers are separate do they measure the speed of both rollers and take an average? or do they measure the speed of one roller only?
If it is the 2nd case moving your magnet to the other wheel would cure the problem.
Davie
no. it wpould be worse - the wheel is not turning so would show 0 mph for all teswted speeds.
fitting another magnet to other wheel and wiring sensors in parallel then putting in 1/2 wheel circum should fix it it theory.
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David Jenkins
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| posted on 27/2/07 at 01:41 PM |
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quote:
Originally posted by 02GF74
fitting another magnet to other wheel and wiring sensors in parallel then putting in 1/2 wheel circum should fix it it theory.
No it wouldn't! There will be times when you'll be getting 2 signals exactly together, so you'll be reading half-speed. In between
the signals could be so close together that the speedo is confused, or they may be perfectly spaced. You'll be continuously going from 1/2
speed, no-quite-sure-what speed, to correct speed.
If it were mine, I'd be tempted to do some basic ratio maths and work out how many magnets and at what spacing would be necessary to make it
work off the propshaft.
Glad it's only one thing to fix now, though.
David
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02GF74
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| posted on 27/2/07 at 02:33 PM |
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I did realise thast there is a possibility of the two signals coincideing but the chances must be pretty low; more of an issue will be the pulse rate
the speedo can handle.
the stumbling block I have is nowing how the speed is calculated from the roller(s).
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mike smith1
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| posted on 27/2/07 at 03:12 PM |
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There should be a facility to lock the rollers so they work in sync with each other, i take it he is measuring the speed on the brake tester.
The brake tester unit will run independantly as for checking the lock up of independent wheels. but should run in sync as for when they are testing
rear wheel drive cars or 4x4's
Mike
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02GF74
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| posted on 27/2/07 at 03:25 PM |
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quote:
Originally posted by mike smith1
There should be a facility to lock the rollers so they work in sync with each other, i take it he is measuring the speed on the brake tester.
The brake tester unit will run independantly as for checking the lock up of independent wheels. but should run in sync as for when they are testing
rear wheel drive cars or 4x4's
Mike
no; pretty sure there is a separate roller for the brake part to the rollers for the speed test.
the speed test rollers surely have to be locakable as there is little drag on the wheels from the "road" so an small difference in drag on
the wheels can cuase the effect I am seeing.
What I noticed is that at the lower speeds the pass. wheel was truning (can't tell if it were at same speed as drivers) but would slow down and
top at hight speed (70).
I can'tbe first person to have a misbalance in drag so dunno.
could a diff problem casue this (can;t see how it can - it truned very freely) or perhaps bad bearing or 1/2 shaft problem? (still think it is the
slightly tight brake drum that is the cause)
[Edited on 27/2/07 by 02GF74]
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RazMan
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| posted on 27/2/07 at 04:11 PM |
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I seem to remember a similar moment during my speed test. My car has the speed sensor in the diff (oem pulse sender) and when it was on the rollers
the offside wheel was turning fine but the nearside was practically stopped. I can see how they would have trouble if your 'slow' wheel
was the one doing the pulses but surely that is down to the way the test was done - it would be fine on the road or on locked rollers. I can't
see how they can fail something that is due to their equipment's inadequacy.
[Edited on 27-2-07 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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Dusty
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| posted on 27/2/07 at 04:45 PM |
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quote:
has anyone used the gearbox take off sensor?
Type 9 gearbox sensor is Hall effect and works fine with my VDO guage. Ask ETB if their speedo will accept Hall effect input?
p.s. You wus robbed!
[Edited on 27/2/07 by Dusty]
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Marcus
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| posted on 27/2/07 at 10:03 PM |
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Surely you'd notice any drag on the brake test?
Marcus
Because kits are for girls!!
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02GF74
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| posted on 28/2/07 at 09:46 AM |
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quote:
Originally posted by Marcus
Surely you'd notice any drag on the brake test?
dunno; depends how much I guess. All I know is that it is not binding i.e. it takes a huge effort to turn or gets hot and smokey when driven. Also
when I have the wheel off and it is on a stand, it can be turned but is not free to move like driver's side, takes a bit of force to overcome
the stiction.
Now on a rolling road, there is extremely little drag on the wheels so my theory is even the small amount I am seeing is enough to slow and eventually
stop the wheel.
I watched the tester operte the kit in the car and passenger wheel would turn from stationary but when the test reached 70, it was slowing down and
stopped (other side must have been doing 140!! ).
I am going to take and see what is the cause - new shoes but used drums and the handbrake adjuster is on its min. position.
I cna try old (more worn) shoes and another drum even though the drum I have seems ok (or swap drums over the sides).
I'm gonna write to SVA appeal to explain the situation to, at the very least, get an extension since my 6 months is up Fri
And to see if there is another centre that has full width single roller or if removing brake drums for the speed test is ok.
I follwed cars slowing down past 30 mph speed cameras and the speed I was showing was pretty close to 30.
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irvined
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| posted on 7/3/07 at 03:58 PM |
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You might want to ask the test center if you can be tested with the car in gear being driven off the engine, this was how mine was tested, i had a
slight drag on the drivers side wheel as well, so you might find thats just enough to get it spinning.
HTH
David
http://irvined.blogspot.com
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