Radius gauge and reverse engineering

[tonyfoale]

I recently posted about some reverse engineering that I needed to do to replicate some classic motorcycle crankcases at
http://www.homemadetools.net/forum/h...029#post120271

Continuing on from that I needed to measure some corner and other radii, there are many possibilities for such tasks, for example MichaelMoore recently posted his templates at
http://www.homemadetools.net/forum/r...348#post122031

This current post is about a set of radius gauges that I built using a digital gauge as the measuring element.



I have put the full story in a PDF which can be seen and/or downloaded from:
Tony's radius gauge
I have also written a simple bit of software to perform radius calculations and that is linked in the PDF file. I will also add a video in the next few days.

[yves78]

Thanks a lot Tony : 2 days ago, I was just thinking to build something similar in order to evaluate a radius.

That's very nice to get an idea of your solution for that.

I take also the opportunity of that reply, to thank you for your pdf explanation documents, always clears and usefuls.

[tonyfoale]

Thanks a lot Tony : 2 days ago, I was just thinking to build something similar in order to evaluate a radius.

That's very nice to get an idea of your solution for that.

I take also the opportunity of that reply, to thank you for your pdf explanation documents, always clears and usefuls.

Glad that you find it useful. If you make something like it be sure to post it here.

[NortonDommi]

Thanks, I've put this in the to do list for Winter.

[Toolmaker51]

Thanks, I've put this in the to do list for Winter.

WELL it's winter here, hint hint. Weeks and weeks worth...

[Toolmaker51]

I recently posted about some reverse engineering that I needed to do to replicate some classic motorcycle crankcases at
http://www.homemadetools.net/forum/h...029#post120271

Continuing on from that I needed to measure some corner and other radii, there are many possibilities for such tasks, for example MichaelMoore recently posted his templates at
http://www.homemadetools.net/forum/r...348#post122031

This current post is about a set of radius gauges that I built using a digital gauge as the measuring element.

I have put the full story in a PDF which can be seen and/or downloaded from:
Tony's radius gauge
I have also written a simple bit of software to perform radius calculations and that is linked in the PDF file. I will also add a video in the next few days.

I can't recall anything on the market or DIY anything like it. Seems Tony, you knock two thirds the competition off before they get in the pit let alone on track. Said other way; He's lapping them right inside the shop?

Further; Jon. Is there a HMT.net logo decal for Tony's machine? What an audience!

[tonyfoale]

I have just enhanced the software to allow calculation of the curve radius and centre coordinates when the XY coordinates of three points on a curve are known.
This is useful if you use the DRO on a milling machine to determine the coordinates of three points. This does not need the radius gauge described above.
The link to the software is the same as that in the PDF RadiusGauge.pdf

[prm]

I have just enhanced the software to allow calculation of the curve radius and centre coordinates when the XY coordinates of three points on a curve are known.
This is useful if you use the DRO on a milling machine to determine the coordinates of three points. This does not need the radius gauge described above.
The link to the software is the same as that in the PDF RadiusGauge.pdf

Tony,

I always read your articles with interest. As I had not used my brain over Christmas, I decided to work out the formula for the radius before reading the appendix.
I ended up with a different and, perhaps, a simpler formula: R=(s^2 + h^2) / 2*h
(where s is half the distance between the probes, h is the value on the indicator and, ^2 means 'squared')

I hope you won't mind if I also note that there are some typos in the pdf file : in the sections were you discuss errors in the indicator reading and errors in measuring the probe spacing, the radius value are not correct.

Regards,
Paul

[tonyfoale]

Tony,

I always read your articles with interest. As I had not used my brain over Christmas, I decided to work out the formula for the radius before reading the appendix.
I ended up with a different and, perhaps, a simpler formula: R=(s^2 + h^2) / 2*h
(where s is half the distance between the probes, h is the value on the indicator and, ^2 means 'squared')

Paul,

I always like to find an easier way regards of where it comes from but I just don't follow your formula. Please show the full derivation. I assume that brackets could enclose the 2*h as (2*h) for clarity and that it is not ((s^2 + h^2) / 2)*h, to remove any ambiguity. In any case I am just not getting it, sometimes we get tunnel vision.

I hope you won't mind if I also note that there are some typos in the pdf file : in the sections were you discuss errors in the indicator reading and errors in measuring the probe spacing, the radius value are not correct.

I never mind it when errors are pointed out. Thanks, I'll check it out later, I am on the wrong computer at the moment.

[prm]

Paul,

I always like to find an easier way regards of where it comes from but I just don't follow your formula. Please show the full derivation. I assume that brackets could enclose the 2*h as (2*h) for clarity and that it is not ((s^2 + h^2) / 2)*h, to remove any ambiguity. In any case I am just not getting it, sometimes we get tunnel vision.

Tony,

I have produced a document with the derivation. It is very convenient that the r^2 terms cancels out and leaves a remarkably simple formula.

Cheers,
Paul