Really Large Radius Gages, Anyone Make Any?

dr_clyde · Jul 16, 2018

I do a lot of reverse engineering. People bring me a broken thing, ask me to make a new one.

Most recently, I had a need to measure what turned out to be a 4.75" radius. There was lots of measuring and math for something that isn't all that critical, where a quick comparison gage would work great.

Seems like most pre-made radius gage sets stop at 1/2", and a few cheap sets go to 1".

I know of the one Baleigh makes that looks like a crossbow. I'm not interested. I want to be able to measure more than 1 direction. Plus, Baleigh can't make a tool worth owning to save their life.

I'm getting close to just making my own, but before I spend all the time and energy, does anyone know of a store bought set? I'd be interested in a set up to 5" radius or so.

If I do end up making my own, what graduations would be useful? I can't see doing every 64th, that would get expensive fast.

Maybe every 1/8" or even 1/4" would probably get me in the ballpark.

I'm drawing a model in solidworks that I should be able to just input different numbers and get a set out of.

Its pretty simple laser work, but I'd still prefer to just buy something.

Alexander · Jul 16, 2018

From my limited experience and research your best bet for an inside radius might be the Baleigh (or similar looking other branded) options.

Outside radius, I'm still no expert but beyond the other baleigh would you be able to use the old fashioned type of calipers, plus a little math if you know the angle measured?

Assuming if you could get halfway around you'd use regular calipers or a micrometer or something.

Alexander · Jul 16, 2018

I know it's not ideal, but if I were in a similar situation on a rare basis, I would probably just print out a few radii full scale on a per project basis. (regular printer or maybe 3d if I'm feeling fancy)

Then again, this doesn't come up often enough in my line of work to make it worth purchasing something. I also have enough round reference items around for comparison that I could get close enough for what I need, so obviously your needs may be different.

dr_clyde · Jul 16, 2018

I've been printing stuff off to use for the last few years, and I've decided I want a dedicated tool set for this.

Plus, paper is hard to keep straight and square, and I'm thinking just some laser cut radii will work for what I need.

But if someone makes a nice set I'd be willing to pay a few hundred bucks and save myself the hassle.

PCustoms · Jul 16, 2018

Empty cereal box, an old school compass and a good pair of scissors.

Start of the "wrong" side of what you think it is and walk yourself in, should be able to get it dead on in a couple iterations.

sweet victory · Jul 16, 2018

Faro arm

PCustoms · Jul 16, 2018

sweet victory said:
Faro arm

Go big or go home!

3d laser scanner

LXCam · Jul 16, 2018

I don't know of anyone that makes them. But a super sized set like this would be really handy to have around. Even if it were in 1/8" increments up to 3" then maybe 1/4" up to six.

dr_clyde · Jul 16, 2018

LXCam said:
I don't know of anyone that makes them. But a super sized set like this would be really handy to have around. Even if it were in 1/8" increments up to 3" then maybe 1/4" up to six.

That's basically what I'm after.

ducksface · Jul 16, 2018

If you make them, I'm good for a set in metal, and I'll buy the layout file.
I'll PayPal.
That will offset the cost of your time.

larry_g · Jul 16, 2018

https://planetcalc.com/1421/

If you know a chord length and height of the segment you can plug it into the above site and find radius.

I assume this is the way you are doing this?

lg
no neat sig line

davewo · Jul 17, 2018

I made these many years ago. I needed to measure axle tubes and forgings in order to make weld-on brackets. Sometimes measuring with a tape or caliper is not possible. They're graduated in 1/8ths and there's enough arc length to determine if a side fits small, big or just right.

View media item 85025

cvairwerks · Jul 17, 2018

I know trick tools has one for 6-144 inches. There is one other source I know of, but will have to get home before I can check it.

Strouty · Jul 17, 2018

davewo said:
I made these many years ago. I needed to measure axle tubes and forgings in order to make weld-on brackets. Sometimes measuring with a tape or caliper is not possible. They're graduated in 1/8ths and there's enough arc length to determine if a side fits small, big or just right.

View media item 85025

Those look slick!

Strouty · Jul 17, 2018

cvairwerks said:
I know trick tools has one for 6-144 inches. There is one other source I know of, but will have to get home before I can check it.

https://www.trick-tools.com/Arc_Master_Large_Radius_Gauge_Set_RG_3600_1341

The only issue I see with this is the width of the radius portion, it could bee too wide for certain situations.

MShaw · Jul 17, 2018

Why not just hold a square against the radius. Measure from the beam to the tangent point and you have the radius. With a good eye it could be used for an inside radius also.

dr_clyde · Jul 17, 2018

davewo said:
I made these many years ago. I needed to measure axle tubes and forgings in order to make weld-on brackets. Sometimes measuring with a tape or caliper is not possible. They're graduated in 1/8ths and there's enough arc length to determine if a side fits small, big or just right.

View media item 85025

I like these, I may make a set like this as well.

dr_clyde · Jul 17, 2018

MShaw said:
Why not just hold a square against the radius. Measure from the beam to the tangent point and you have the radius. With a good eye it could be used for an inside radius also.

This is basically what I do now. I just want something fast and easy. Which isn't to say measuring with square isn't fast, I just like the ease of use of regular radius gages and they just aren't big enough.

JMLangford · Jul 17, 2018

This is what I use.......

.

larry_g · Jul 17, 2018

Above is a neat tool that does it all for you. However if you use a caliper and know the length of the jaw to the beam you can get the cord length and the height (jaw length) by having the caliper touch at three places, the ends of the jaws and the beam. If the radius is to big then touch the jaws to the part and measure from the beam to the part and derive the height. Good for outside radius.

Like said by Davewo, won't work in all situations but it will in a lot. Davewo's set is to the nearest 1/8 and from there he can get what he needs. The method used depends on the required accuracy of the part. A lot of difference between the radius needed on a log for a log cabin and the part the machinist has to produce with tolerances measured in arc seconds.

lg
no neat sig line

dr_clyde · Jul 17, 2018

I should clarify. I don't plan to use these for precision applications. I use things like this for stuff like tank corner radii and reverse engineering weldments. Just something fast and easy to get me in the ballpark.

For precise machine work, I usually use calipers and gage pins to measure chords and stuff like that.

franzdom · Jul 17, 2018

3D print...

dr_clyde · Jul 17, 2018

franzdom said:
3D print...

I don't have a 3d printer. I don't really want one either. They are an expensive distraction for what I do.

MoonRise · Jul 17, 2018

Up to 54" radius

http://fabtooling.com/us/accessoires-accessories/radius-gauge-jauge-rayon/sm-big-arcmeter

Up to 27" radius

http://fabtooling.com/us/accessoire...auge-de-mesure-digitale-pour-rayons-diametres

2.5 to 30" radius

https://www.trick-tools.com/Arc_Master_Small_Radius_Gauge_Set_RG_750_955

6 to 144" radius

https://www.trick-tools.com/Arc_Master_Large_Radius_Gauge_Set_RG_3600_1341

jsteih · Jul 17, 2018

https://davistoolz.com/product/large-radius-gauge-set-16-sizes-4-116in-to-5in/

dontlifttoshift · Jul 17, 2018

They have another one with different sizes. 40 bucks for the pair.

https://www.trick-tools.com/Radius_Check_Gauge_TTRCG_366

dontlifttoshift · Jul 17, 2018

I have a set, it measures radii. It does so with all the accuracy that I think the OP requested.

There was lots of measuring and math for something that isn't all that critical, where a quick comparison gage would work great.

jimreed2160 · Jul 19, 2018

A mid sized radius set exists now in your pantry. The cans are great for woodworking. I just grab a can with the size I need and use it to trace. If you save tomato paste, tuna and coke cans you can build a nice set in no time.

jmarkwolf · Jul 19, 2018

JMLangford said:
This is what I use.......

.

Me too.

tarbellb · Jul 19, 2018

davewo said:
I made these many years ago. I needed to measure axle tubes and forgings in order to make weld-on brackets. Sometimes measuring with a tape or caliper is not possible. They're graduated in 1/8ths and there's enough arc length to determine if a side fits small, big or just right.

View media item 85025

These are great! Gave me a idea, if you are going to make your own, perhaps a more compact and less prone to losing one style like this-

(super quick mockup for illustrative purposes)

ptgarcia · Jul 19, 2018

How about a set of drafting railroad curves? Mine start at R=3" and go up to R=200".

Really Large Radius Gages, Anyone Make Any?

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