Hi
My renault clio speedo always shows at least 4mph instead of 0mph- even when the car is stopped at traffic lights - im worried this might be affecting the speed i am actally doing when driving - can you help?
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Have you ever noticed the little posts along the side of the hard shoulder? They have arrows on, pointing to the nearest emergency telephone, and they are 100m apart.
With an assistant, drive along the motorway at an indicated constant 120 km/h (which is 72 mph). In one minute, you will pass 20 of these posts if your speedo is exactly right. As long as you pass at least 18 of these posts within one minute, travelling at 120 km/h, then your speedo is no more than 10% fast, which is fine.
If you pass more than 20 posts in 1 minute, your speedo is reading slow, which is something to worry about. But I bet it doesn't.
Rob F
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You should actually pass 21 of these (100m spacing between each). This will be 20 x 100 spaces or 2km. Sorry to be pedantic, but it is important.
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My Rev counter won't work at all and the Rear view mirror has fell off - you are lucky !!!!
Does anyone know how to fix the rev counter ?
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Not normally difficult. Does anybody know if it is electric or mechanical ?
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Actually, you will start level with one and then finish level with another, passing others in between.
Essentially if your speed is exactly accurate you will only pass 19 posts and see 2 others (level with you).
Pedantry at its best.
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Wendy,
not sure if it's any help, but both my old Zx's read 5mph or so at stationary. The citroen dealership said it was fine, they all do that but show the correct speed above 10mph.
If you're worried, get someone with a GPS unit to sit in the car and see if the readings match. There was a long thread this week about the tolerances, search under GPS as I think I was rambling about it on that thread too.
Lee.
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Sid
No, no, no! If the speedo were exactly correct, you wouldn't get past the 21st post within one minute of the first. At best, you'd be exactly level with it.
I agree that it takes 21 posts 100m apart to demarcate 2km. But you'll only PASS twenty of them in 60 seconds at precisely 120km/h.
Rob F
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Mark
You pass the first one too. Otherwise you'd have a standing start.
Pass that crown back....
Rob F
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No, its mine.
The car actually, by your latest definition, probably passes 50 of the things at least. Since you are not allowed to stop on a motorway for no good reason, and 50 is probably likely between two junctions.
For the relevant period of time, you will begin level with the first, pass 19 and complete level with the 21st (assuming speedo accuracy, error etc.)
You will leave 1, pass 19, arrive at 1.
I'm right, you're wrong, gimme that crown back.
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Mark
I'll let you polish it for me. Then you can return it.
If you look at my original message in this thread, I did not specify that the timer started level with any post. You can start it when you like.
However, it matters not.
In our imaginary, pedants' world, let's assume that we actually can start the clock at any precise point we like. If we start it where the first post ends - the edge furtherest along the direction of the carriageway, then in exactly 2km we will have reached the far edge of the 20th post (not counting the first). We've passed the 20th post. And 19 others.
If we start the clock at the nearest edge, then we never make it to the nearest edge of the 20th post, but we pass the width of the starting post as well as the following 19. 20 in total.
In 60 seconds at 120km/h, you will pass 20 posts - whenever you start the clock. The only way you could pass only 19 is if they were infinitely thin. Which they're not, of course.
Rob F
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Most cars speedos are out by a bit and they are always on the right side.
i.e. indicated 60 will really be 55/56 - don't worry........
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You could always find a cop car, hold your speed at an indicated 90 past it and see what plod tells you it is when he pulls you in and fines you.
Similar technique through a speed camera.
Perhaps slightly less stressfull and painful than trying to follow the last ten replies!
:-)
Mark
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Marykmarkn,
thanks for a bit of sunshine there
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Rob, Rob, Rob
If passing twenty of them was sufficient, then you could start .9 before one and .9 after the last or equally .1 before and .1 after, a difference of 1.6 units.
This is hardly accurate.
No, one needs to start when level with 1, pass 19 and stop when level with the last.
And they don`t need to be infinitely thin, so long as you start at some point across one and finish at a similar point across the other, then you have not passed either of these two posts, you have simply left one and arrived at the other, PASSING the 19 in between.
Hence, the only truly accurate way is to ensure that you pass 19, and ONLY 19, but see 21 at close range.
I accept your apology, now get your hands off the crown.
And by the way, I notice some of the diamonds missing from this crown since you`ve had it. Give 'em back. All of them.
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Mark, Mark, Mark,
The '20 posts in 60 seconds at 120km/h' test is practical real world advice on how to reassure yourself that the speedo is acceptably accurate. But back in pedants' world, you're still so, so wrong.
If you start 0.9, or 0.1, or any other distance before or after a post, you will *never* encounter more than 20 posts in 60 seconds at reference speed. If you start .9 before the first, you will finish .9 before the 21st. Which gives 20 in the middle. If you pass 20 posts (no more and no less) in 60 seconds, you can be sure that your speedo is correct +/- 5%. If you start the clock at the first post, you can be more accurate. And if you hit the 21st post (or 20th *after* the starting post) your speedo is pretty damn accurate.
As to passing posts: when you start a race, do you start behind the line, or on it? And do you finish that race if you don't cross the finish line - or pass it rather.
Thank you for conceding so gracefully. Have a tissue to dry your eyes.
As to those diamonds, they're staying off. I want to look like the master of pedantry, not Liberace.
Rob F
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Rob F wrote:
> As to those diamonds, they're staying off. I want to look
> like the master of pedantry, not Liberace.
>
> Rob F
Wasn't Liberace the master of pederasty?
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Rob F wrote:
> As to those diamonds, they're staying off. I want to look
> like the master of pedantry, not Liberace.
>
> Rob F
Wasn't Liberace the master of pederasty?
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Cor, - how you all do go on! Funny, tho'.
Rita
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oh Rob
Firstly dismissing your real world issues;
How can you posible know whether you are 0.1 or 0.9 before or after a post ? It isn`t marked. The only possibility you have is to identify when you are next to a post, since given that they are only a couple of inches wide you can be pretty accurate about positioning.
And then moving on to your pedantry;
And I appreciate your assistance since you started arguung with yourself, but really I don`t need the help. Just this once though...
>you will *never* encounter more than 20 posts in 60 seconds at reference speed.
>And if you hit the 21st post (or 20th *after* the starting post) your speedo is pretty damn accurate.
So which ? "never" or only if "your speedo is pretty damn accurate" ?
However, whichever, hitting the 21st post would break it and deeply confuse the next person to try out their speedo on that stretch, since they would only pass 18 posts, encounter 2 more, and never understand about the 21st post imbedded in the front of your Reliant.
Nonetheless, since you have now mastered the idea that you will encounter 21 posts, we are only a short hop from getting you to understand that we pass 19 of them and encounter 2 more.
For your race analagy, the photo finish(s) device they use, photograph people on the line as a measure of if they win.
However, assuming only two lines on a track then it is clear that during the race you will not cross more than one of them and potentially neither, depending on whether the race begins before, on or after the start line.
Since you are clearly a little Liberace-phobic, then I'm surprised that you bought the sequinned cape to match the crown.
I have to go, there is a small group of people outside discussing your abject surrender and they`re blocking the road. I need to move them along.
Mark.
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Is it not illegal to drive without a working speedo (within its legal accuracy tolerance)?
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Paula's Speedo works fine - its the Revcounter which has thrown the towel in
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Excuse me there is a guy in a red van outside here wanting to know all about these 19/20/21 posts in 60 seconds.
He's muttering something about should be grateful if you get two in one day, think he's from Consignia. ;-)
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Hmm....I've never managed that rate of posts.
I do need to fence in a bit of grass this weekend though. 120ft of fence with posts at 12ft intervals...wonder how many posts I'll need?
David
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Never mind the posts - they are not always that evenly spaced, especially near intersections.
Have a look for the measured mile indicators. Circular discs, fairly low to the ground. Start with a yellow disc, with quarter segments filled in with red at quarter mile intervals, final being a red disc. There's one on the M4 between J13 and 14, and I'm sure I've seen others, but can't remember where.
I assume they're used by the Police for speedo calibration?
Regards
john
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Mark
How your concessions bring your argument tumbling down. Children, gather round and learn from this man's mistakes.
It doesn't matter whether you are 0.9 or 0.1 away from a post - this was an irrelevant concept intoduced by yourself, with which you have got yourself terribly confused.
Now repeat after me. You don't need to start the timer at any particular place. And if you *pass* 20 posts (in 60 secs at 120 km/h), your speedo is accurate enough not to worry about.
But if you start it level with post no.1, and you hit post no. 21 in 60 seconds travelling at a constant 120 km/h, then your speedo is accurate to within 0.000025% (taking your assumption that a post is a couple of inches wide). Which is pretty damn good, eh? (Shame about the bodywork)
And don't you realise that my Reliant isn't allowed on the motorway?
Those people outside your place - are they wearing white coats, with hyperdermic needles in their top pockets? Don't fight them Mark, they have come to help you.
If you must wear glitter with the outfit, at least use a matching colour.
Rob F
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Rob,
>
>It doesn't matter whether you are 0.9 or 0.1 away from a post -
You're right it doesn't matter the distance, provided it is the same at the beginning and ending.
However, in the real world, the one your mother told you about, that isn't easy. That's why you would need to use the posts, and being next to the first and last and passing the 19 in the middle.
>Now repeat after me. You don't need to start the timer at any particular place.
No you don't. But since you are driving along then the only chance of being accurate is to start at a post and hopefully finish at another.
>And if you *pass* 20 posts (in 60 secs at 120 km/h), your speedo is accurate enough not to worry about.
As opposed to accurate ? Oh, how quickly we comprimise !. Whereas if you passed 19 posts and started and stopped at two others in 20secs/120kph then your speedo could be assumed even more accurate than your rather hit and miss, near enough is good enough approach.
>But if you start it level with post no.1, and you hit post no. 21 in 60 seconds travelling at a constant 120 km/h, then your speedo is accurate to within >0.000025% (taking your assumption that a post is a couple of inches wide).
You see, you got there in the end, now that didn't hurt *so* much did it ?
The white coats had come to help. Apparantly some doctor from the UK has sent out an alert that one of his more pedantic, but sadly misguided, clients has checked himself out of the clinic again.
The white coats were worried about the stress it could cause me.
By the way, they had a message from your doctor who said keep taking the penicillin and don't worry about the twitching, it will wear off.
Of course I have to wear glitter, you took all the pink silk and rubber patches off.
Mark
p.s. in reply to your e-mail apologising profusely and begging me to allow you to win this discussion with your rather erroneous points, then I am afraid the answer is no. And since you asked, yes I am very good looking. Why ?
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Mark
>You're right
A very good start.
>You see, you got there in the end
I was there in the beginning. Glad you could make it too.
>You took all the pink silk and rubber patches off
You left vaseline all over them - what else could I do?
Rob F
PS That's not a mirror on your padded cell wall, it's a picture of me. Confronting your tormentor is part of the healing process, so your psychiatrists tell me. And yes, thank you. I am rather handsome.
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Rob,
> I was there in the beginning. Glad you could make it too.
So, we're agreed then; an absolutely accurate speedomoter will perform in a time/distance test as follows; the test will begin at one post, pass 19 and complete at the final post. A total of 19 passed and two seen.
> You left vaseline all over them - what else could I do?
That wasn't vaseline.
Mark.
p.s. please stop sending me these contrite, begging, grovelling e-mails. It is becoming embarassing. And no, I never do that on a first date.
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Rob/Mark,
You've both got higher than the bracket halfway up the cistern pipe, isn't that enough?
David
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Mark
>A total of 19 passed and two seen.
As you drive past them. 19 + 2 = 21. At last! I'll instruct the nurse to take you off medication.
>That wasn't vaseline.
How *do* you do those apostrophes, as you type with you nose while wearing a strait jacket?
Rob F
PS Just because you keep sending me obscene pictures of yourself, doesn't mean you'll get some of me.
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Mark,
>A total of 19 passed and two seen.
>
>As you drive past them. 19 + 2 = 21. At last! I'll instruct the nurse to take you off medication.
Oh dear, how sad. Once more, with feeling. You may, or may not drive past them and 500 others in the course of your journey. However, this is a distance/time test, and within that test you will pass 19 and see 21. Its not difficult, try it. In fact, dust off your Reliant and try it on the M25 tonight, in reverse.
>>That wasn't vaseline.
>
>How *do* you do those apostrophes, as you type with you nose while wearing a strait jacket?
I have often been referred to as somewhat of a clever-dick.
Mark.
p.s. ref: the last mail & picture you sent; How much did you have to pay the Shepherd for him to let you do *that* ??
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Mark
>Mark,
You seem to be posting messages to yourself.
>You may, or may not drive past them and 500 others
Not within the 2000m reference distance. It is tragic that one of such apparent intelligence cannot grasp such a simple fact.
During the test, at least 20 reference points are passed if accurate. You may well see a few more on a clear day, but that's utterly irrelevant.
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Sorry, just laughed so much at the idea of accidentally accusing yourself of sheep-s****ing I hit return. Get well soon, mate.
Rob F
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Finally you admit defeat and capitulate. Pity you only did it in e-mail, not in the Phorum, but I gues you deserve to keep some pride.
And as of right now, I am firmly of the belief that the correct number of posts is 42.
Right, off the the Freelander thread..........
eyethenkewe and goodnight.
The Electric Monk.
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you don`t *really* want to set us off again, do you ?
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Ian,
Careful, if Liberace were alive today he would be sueing your ass off for a comment like that!
Serious comment actually, he spent a lifetime in litigation against those who accused him of being a woolly wooftah.
Stuart
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