Hi Gang,
I work on this problem for a long time. I wonder if we have the size of a tire e.g. 16.00R20 as used on HEMTT truck, can we calculate the outside diameter from this. I know that HEMTT tire are approx. 36 mm in diamater. So what is the outside diameter of a 29.5R35? Is there a formula to calculate this?

I may be wrong (maybe even certainly) but I think that the Rnn (R20 or R35 means the radius of the rim, measured as half the diameter of the hole in the rubber tire. The rim and tyre overlap a bit so the maximum diameter of the R20 rim will be maybe an inch larger than the diameter of the hole.
The other number means the width of the tire measured inside the rim (guessing a bit here ...)
The total diameter of the rubber tire then depends on the profile, older tires have a 100% ratio between rim width and the distance from the hole to the patterned surface of the tire.
Modern tires usually have a lower profile, like 70% or 60%.
So Rnn x 2 + 2 x the other number x the profile percentage

http://www.militaryoffroadtires.net/product-p/t-1600r20xzl.htm
This page claims that the tires are 53 inches tall (remember that rubber will get worn off so that the diameter of a used tire is less than a factory fresh one)


/ Robin

Ignore my gibberish above !
Rnn is not the radius or diameter.
I found a pdf-file for Bridgestone tires where the recommended rim for 29.5R35 is given as 25.00/3.5 rim/flange (inch).

See http://www.goodyearautoservice.com/content/content.jsp?pageName=TireSize seems to be for passenger cars (PKW)

Found a table of tires from some chinese manufacturer:
https://sc01.alicdn.com/kf/HTB1g68UIpXXXXbEXFXXq6xXFXXXj/202069897/HTB1g68UIpXXXXbEXFXXq6xXFXXXj.jpg
They claim that the overall diameter of 16.00/R20 is 51.5 inches or 1309 mm.

/ Robin

The webpage of that Chinese manufacturer shows an image of an HEMTT and they say they can provide military tires
https://www.alibaba.com/product-detail/Chinese-famous-brand-ADVANCE-SAMSON-brand_60267988908.html

This dutch webpage gives other measurments for Michelin 16.00R20
https://www.heuver.com/item/2258/16-00r20-michelin-xzl-170g-tl

Maybe the easiest way is to Google each individual tire size and manufacturer since the measurments seem to differ a little.


/ Robin

Hi Robin, thanks for clarifying. I did a little search and found out the a Bridgestone 29.R35 tire has an outside diameter of 2120 mm, aprox. 60 mm in scale. I have the crazy idea to build a Kalmar RT 240 RTCH, so all I need to do is building 4 tires from scratch, the rest of the project is a piece of cake then.

'Crazy idea' sounds about right

That's a big piece of cake

Which building method are you planning to use for the tires ?

/ Robin

I actually cut out round slices of 1mm sheet and laminated 22 of them for the required thickness. Size of the model tire in 60mm diameter and 22 mm wide. I can use a lathe on the job to make the thing round. Then comes the task of glueing the profile. Making the rim is another task at work. I am still undecided if I cast the prototype or make all four tires from scratch. Like said it`s just an idea now.

I was mostly curious about the tire tread(lauffläche).
I have been thinking about making treads by glueing bits of pattern to a flat strip and then wrapping the strip around a tire disc. With access to a small CNC milling machine it might be possible to produce a tread strip by milling.

Keep us posted on the progress with the tires
/ Robin

I take my prototype plastic junk tomorrow to the job and use an industrial lathe to make a wheel out of it. Next task is to extract and enlarge drawings from the RTCH TM. I hope I am not struck by the models size.

I guess you don't plan to just scale up the Balaton one



H.P.

Interesting find! Just scaled up the drawings that I have and bought me some 1.5 mm sheet for the start.