Curious circular slide rule - UK Vintage Radio Repair and Restoration Discussion Forum

neutronic · 9th Jul 2019, 9:37 pm

Something surprises me.
I just bought this military slide rule for fun. (and it was cheap).

The backside gives most popular formulas.In top is the explanation for sin,cos and tn.
Instead of giving the right angle in 90 degrees,it says 1600 pro mile or 0/00.
What does this mean or is this normal in the military artillery?
Jard N.

Andrewausfa · 9th Jul 2019, 11:15 pm

Nice rule, made by ALRO in Holland. The 'pro mile' bit is the same thing as something you may have heard called 'mils'. 1600 mils is 90°, 6400 mils to a NATO circle.

Andrew

neutronic · 10th Jul 2019, 10:20 am

Thanks Andrew.

I did not know that,I have no military background.
In fact,I found this slide rule while looking for one special model I knew from the past.
A pocket model made to the specifications by the firm I used to work for.
At one side the relation between L, C and frequency.
And at the other side a voltage across a resister giving a certain dB value.
Even today very useful
But this model is rather scarce.
Jard N.

Pictures:Alro 746 circular slide rule 6cm diameter

9th Jul 2019, 9:37 pm	#1
neutronic Pentode Join Date: Oct 2009 Location: Bergen, North Holland, The Netherlands Posts: 180	Curious circular slide rule Something surprises me. I just bought this military slide rule for fun. (and it was cheap). The backside gives most popular formulas.In top is the explanation for sin,cos and tn. Instead of giving the right angle in 90 degrees,it says 1600 pro mile or 0/00. What does this mean or is this normal in the military artillery? Jard N. Attached Thumbnails Last edited by neutronic; 9th Jul 2019 at 9:53 pm.

9th Jul 2019, 11:15 pm	#2
Andrewausfa Octode Join Date: Dec 2010 Location: St Ives, Cambridgeshire, UK. Posts: 1,180	Re: Curious circular slide rule Nice rule, made by ALRO in Holland. The 'pro mile' bit is the same thing as something you may have heard called 'mils'. 1600 mils is 90°, 6400 mils to a NATO circle. Andrew __________________ Invisible airwaves crackle with life. Or they should do. BVWS Member

10th Jul 2019, 10:20 am	#3
neutronic Pentode Join Date: Oct 2009 Location: Bergen, North Holland, The Netherlands Posts: 180	Re: Curious circular slide rule Thanks Andrew. I did not know that,I have no military background. In fact,I found this slide rule while looking for one special model I knew from the past. A pocket model made to the specifications by the firm I used to work for. At one side the relation between L, C and frequency. And at the other side a voltage across a resister giving a certain dB value. Even today very useful But this model is rather scarce. Jard N. Pictures:Alro 746 circular slide rule 6cm diameter Attached Thumbnails