Measuring PCD holes

[JAParticipant @ja]

Euclid would have drawn it out. Classical geometry is just drawing and comes from Euclid's work. What ever is said it is quite valid and not accurate (probably an order of magnitude less than the measurements taken from the hub).

JA

Edited By JA on 28/11/2016 12:58:07

Edited By JA on 28/11/2016 13:00:13

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JA on 28/11/2016 12:56:54:

… What ever is said it is quite valid and not accurate …

.

Sorry, JA … I don't quite get your point ^^^

Could you please clarify ?

MichaelG.

[SillyOldDufferModerator @sillyoldduffer]

Rod and JA : that's exactly what I thought. Then I read about the "Bloom of Thymaridas" in Wikipaedia's 'History of Algebra'. Although based on geometry and not a fully developed algebra, it does include solving simultaneous linear equations in Euclid's time and place. That's my interpretation anyway. But I admit my maths knowledge is sadly limited.

Dave

[Nick_GParticipant @nick_g]

Posted by David Standing 1 on 28/11/2016 12:36:01:

Friend of a friend needs to be extremely careful in how he has spacers made and fitted if he doesn't want sheared wheel bolts/studs and then the wheel parting company at speed.

.

Yes.

TBH I thought their use had been banned years ago back in the late 70's – early 80's due to their use and other modifications causing poor handling and effecting the whole balance of the car. Not to mention stud shearing.

I 'think' this craze all started in the UK of putting flares onto wheel arches, widening the wheel base, lowering the front and jacking up the rear due to the US TV series Starskey and Hutch.

Of course said 'victim' car had to then have the obligatory stripe, stick in sun visor with names on and most importantly a monster size CB antenna.

Nick

[Steven VineParticipant @stevenvine79904]

Posted by David Standing 1 on 28/11/2016 12:36:01:

Friend of a friend needs to be extremely careful in how he has spacers made and fitted if he doesn't want sheared wheel bolts/studs and then the wheel parting company at speed.

The wheel should be located on a spigot that forms part of the hub, as it will be as originally fitted on the car by the manufacturer. If you are making spacers, the spacer needs to be bored with a female spigot housing on its inside face that has a tight fit to the hub spigot. In turn the spacer also needs to have a hub centric spigot machined on its outer face to locate snugly in the wheel centre.

Both female and male spigots on the spacer need to be exactly co-centric with each other, or it can set up a centrifugal imbalance which can be impossible to balance out, and be dangerous as it puts a lot of loading force on wheel bearings and ball joints.

ALL of the wheel bolt /stud clamping effort is designed to be only for that, in other words neither the studs/bolts or their cone shaped mating surfaces are designed to take any lateral shear force, the hub to wheel spigot should take care of that.

If you know all this already, my apologies.

Thanks David. I found that very interesting and informative.

Steve

 

Edited By Steven Vine on 28/11/2016 13:42:32

[David Standing 1Participant @davidstanding1]

Posted by Nick_G on 28/11/2016 13:27:36:

Posted by David Standing 1 on 28/11/2016 12:36:01:

Friend of a friend needs to be extremely careful in how he has spacers made and fitted if he doesn't want sheared wheel bolts/studs and then the wheel parting company at speed.

.

Yes.

TBH I thought their use had been banned years ago back in the late 70's – early 80's due to their use and other modifications causing poor handling and effecting the whole balance of the car. Not to mention stud shearing.

I 'think' this craze all started in the UK of putting flares onto wheel arches, widening the wheel base, lowering the front and jacking up the rear due to the US TV series Starskey and Hutch.

Of course said 'victim' car had to then have the obligatory stripe, stick in sun visor with names on and most importantly a monster size CB antenna.

Nick

Nick

I was there, been there done that .

And that's how I know .

[Neil WyattModerator @neilwyatt]

Cor, you lot don't 'arf make it complicated!

Use my method and if it doesn't come very close to a 'sensible' dimension, take the average of a few measurements.

Neil

[JAParticipant @ja]

Posted by Michael Gilligan on 28/11/2016 13:08:48:

Posted by JA on 28/11/2016 12:56:54:

… What ever is said it is quite valid and not accurate …

.

Sorry, JA … I don't quite get your point ^^^

Could you please clarify ?

MichaelG.

MichaelG

I have been sitting for about an hour trying to think of how to reply to this.

My first draft was on how the Greeks would have solved the problem arithmetically. I had to retreat on that one since it appears that I am, or even we as modern man are, wrong to consider equations as algebra. Wikipedia, as Dave says, suggests that the ancients solved equations. I think that is a tall order. OK they could multiply and divide (and used squares, cubes, square roots, cube roots and pi) but they were hindered by their numbering system (I haven't a clue on how to add and subtract using Roman numerals). Romans used fractions, so I guess the Greeks did, but we are taught that the Arabs (not the French) introduced the decimal system. Given all this drawing the problem out as a piece of geometry makes full sense.

Return to your query, the accuracy of the result is limited by the drawing accuracy. If it was drawn full size the accuracy would be no better than a hundredth of an inch while the measurement accuracy would hopefully be to the nearest thou.

Neil – We can make the simplest question very complicated.

JA

[Roderick JenkinsParticipant @roderickjenkins93242]

Posted by SillyOldDuffer on 28/11/2016 13:20:51:

Rod and JA : that's exactly what I thought. Then I read about the "Bloom of Thymaridas" in Wikipaedia's 'History of Algebra'. Although based on geometry and not a fully developed algebra, it does include solving simultaneous linear equations in Euclid's time and place. That's my interpretation anyway. But I admit my maths knowledge is sadly limited.

Dave

Interesting link, thanks.

It's algebra, Jim…

Rod

[MuzzerParticipant @muzzer]

Posted by KWIL on 28/11/2016 12:09:59:

Muzzer

That is interesting, but I have never seen a wheel/tyre balancing machine that did anything other than use a tapered centering plug to pick up with that central bore.

I gathered(?) that this was an old vehicle, possibly around the same vintage as various Renaults, Citroens, Fiats etc that had no centre hub in the first place (1970-80s IIRC). Look them up if your memory fails you. So it's possible that the feature wasn't used for location although I agree it's unlikely on a vehicle like this.

Renault 4, 5, 16, 17; Fiat 500, 600, 127, Shitroen 2CV / Ami etc etc….

Edited By Muzzer on 28/11/2016 16:13:55

[Jon GibbsParticipant @jongibbs59756]

Posted by Neil Wyatt on 28/11/2016 15:05:10:

Cor, you lot don't 'arf make it complicated!

Use my method and if it doesn't come very close to a 'sensible' dimension, take the average of a few measurements.

Neil

In the general case I still think you'd want to take an average of the values you obtain from each pair of holes if you're using the perpendicular bisectors method because there'll inevitably be some variation in hole dimension and position as well as in your measurements.

It's especially the case when trying the work out the PCD from blind tapped holes – I recently had that problem when trying to make a backplate for an old 3-jaw chuck where each hole ID measured differently and I didn't have any of the correct BSW threaded rod I could sacrifice.

Jon

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JA on 28/11/2016 15:46:35:

Could you please clarify ?

MichaelG.

MichaelG

I have been sitting for about an hour trying to think of how to reply to this.

…

Return to your query, the accuracy of the result is limited by the drawing accuracy. If it was drawn full size the accuracy would be no better than a hundredth of an inch while the measurement accuracy would hopefully be to the nearest thou.

.

Thanks, JA … I didn't mean to cause you too much bother.

I do accept your point about drawing accuracy [although, if carefully planned & executed, I believe this exercise could be done to better than a hundredth of an inch], but what particularly interests me is that the method is theoretically perfect, and therefore any inaccuracy is attributable solely to technique.

MichaelG.

[JAParticipant @ja]

Thanks. I realise I have a good item for my Christmas present list – a good comprehensive history of mathematics.

JA

[JasonBModerator @jasonb]

Nick might just be easier to cut the disc out of the wheel rim and have your welder mate put it back in with the new offset

[simondavies3Participant @simondavies3]

Posted by KWIL on 28/11/2016 12:09:59:

Muzzer

That is interesting, but I have never seen a wheel/tyre balancing machine that did anything other than use a tapered centering plug to pick up with that central bore.

Ah, not so……I have had exactly this problem which took me some time to understand – balancing tyres at the tyre centre produced a clearly out of balance wheel.

Eventually I took the car to a performance focused place and they took one look and got out a 5 way 'sliding spider' affair that they installed in place of the cones. This looks like 5 studs on some form of geared backplate that expand in unison, maintaining their centre distance. Add wheel and then screw up 5 nuts and balance.

Cause of lots of grumbling at the tyre place since it is a non trivial exercise but perfect result.

Wheels are of GKN origin and were originally shod with Avon tyres way back in 1973.

[KWILParticipant @kwil]

Scroll operated spider, but at a performance focused place. Now we all know where to go. Thank you

[simondavies3Participant @simondavies3]

I see the trade refers to them as "centreless wheel balancing adaptor" – like this:

This came from the 1st search result: https://www.garageequipmentonline.com/products/tyre-changer-and-balancer-options/centreless-wheel-adaptor

Hope that is clearer.

Simon

[MuzzerParticipant @muzzer]

That looks familiar. Not used much these days of course – now a minority sport, for good reason.

[CirclipParticipant @circlip]

Posted by Neil Wyatt on 28/11/2016 15:05:10:

Cor, you lot don't 'arf make it complicated!

Use my method and if it doesn't come very close to a 'sensible' dimension, take the average of a few measurements.

Neil

But didn't it take 10 pages to determine the tapping size drill for an M8 thread? and for the great unwashed, the centre hole and the mounting stud holes will be punched at the same time. Wersant wide wheels the replacement for hanging them out on studs?

Regards Ian.

[HopperParticipant @hopper]

What's wrong with laying the wheel on the piece of spacer material and marking the five holes on the material with a sciber, then finding the centres of the five scribed holes using dividers, or by drawing a box around each circle and scribing the diagonals, then centre punching and drilling accordingly? It's a spacer isnt it? Holes can be drilled clearance size on the studs.

[Mark CParticipant @markc]

Small wheels may be blanked in one pass but not all are done that way. Here is a very interesting photo essay showing large 4×4 wheel manufacture from strip to paint booth **LINK**

Balancing is intersecting in it's own right (especially dynamic balancing) and the effects of altering wheel width, offset and diameter have profound effects on vehicle handling. It is a very interesting subject and there is considerably more to it than might at first be apparent.

Mark

[CirclipParticipant @circlip]

Centre hole is sized at same time as mounting stud holes. Only shows primary centre location for dishing rest of details.

Regards Ian.

[Mark CParticipant @markc]

Ian, I would expect there to be some method to ensure concentricity but I imagine they may well form the up-stand at the hub center and form the bolt/nut seats at the same time having punched the holes previously. They may also blank and form at the same time but that would require significant press capacity as I am certain you already know. Unless they have a standard production sequence then each manufacturer will have their own variations on a theme depending on product and press availability.

Mark

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