[choppergirl]

Someone on Homebuiltairplanes sent me this antique 1986 Ball M-20 wrist vario Serial No. 8810 today (US Patent No. 4,086,810), along with a bunch of 1.8mm pop rivets and stuff. There's no other picture of one of these on the internet anywhere, so I thought I'd post it... it works!

http://dcim7.peachcountry.com/DSC_0735.JPG
http://dcim7.peachcountry.com/DSC_0736.JPG
http://dcim7.peachcountry.com/DSC_0737.JPG

http://www.ssa.org/FinalGlide?id=2747
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=9&f=G&l=50&co1=AND&d=PTXT&s1=4,086,810&OS=4,086,810&RS=4,086,810

That 9volt battery mount wasn't aftermarket grafted on there by the user, that's how it was built by Richard Ball.
Note that he sprung for some heavy custom ABS plastic mold housing.

CHOPPERGIRL
http://choppergirl.air-war.org
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http://alice.air-war.org

[Rick Masters]

Very interesting, choppergirl, and nice photos.
I remember calling Richard Ball in 1986 and asking him if he was interested in incorporating one of Alan Fisher's Thermal Snoopers, which I was testing that year, into his devices.
He was interested at the technical level but felt that hang gliding was such a niche market that it offered little potential for profit.
(See page 61 for his line-up in 1984:
http://ushawks.org/forum/viewtopic.php?f=2&t=2636&start=10&sid=2183635081db229351a44c2b6e55d932#p19263
I have never actually seen one of his wrist variometers.
He may have been commenting on the low sales he was receiving on the new product.
I suspect cross-country pilots of the day would have preferred, as I did, to have my instrumentation mounted to a downtube rather than have it interfere or get covered by high altitude clothing.

[choppergirl]

Well, it has an over kill of enough velcro strap, could could actually wrap it around on the outside of your cold weather jacket. It fits around my bulky motorcycle jacket with plenty of velcro to spare. That explains to me now, why there was so much extra velcro strap...

It is a rather bulky device on a bare wrist, however. I think it would make a good coversation starter. "Nice watch you got there. What does it do? Tell time? Cool. Check out mine..."

~

I was hoping it would look like the Ball M-19, but it looked like nothing of the sort.



At first I thought it was broken, until after playing with it, I realized variometers were simple back then. It beeps for 5 seconds on startup, goes quiet, and then only beeps on rise... not on descent or static altitude. If I hold it at the ground, and lift it to my head, it will beep, and then settle down.

I haven't tested the meter yet, as I assume it is averaged over a few seconds so will not show any reading with my quick lift tests. If I get around an elevator I'll test it, and hope the meter still works. No way to calibrate the meter, but there seems to be no reason to do so... it rests at zero. Impressive it still works, for its age. There's not a whole lot to the circuit board, one small IC chip and 20 or so components.

[Bill Cummings]

I've never seen the top one before.
Any brand works good on the bar (bartender type) if you want to be the first person to notice that a possible date is opening the door.
When the door opens the vario goes wild and you can check out the prospects.