Hello all, I just picked up this Waltham A8 Ground Speed watch. As you can see it comes with its original box and cloth bag as well. Can someone tell be a little of this watch's purpose. I know it is a "ground Speed" watch and was probably used to time the take off time of aircraft? Can someone eleborate on this piece such as it's use, where it would been used (aircraft carrier ect...) and whom might have known how to use it. I probably paid to much for this piece ($87)(as most of my watches) but I could not pass up this opportunity with such an original piece, its condition and boxes. Cheers all!

Rear case

I also have ashock absorber in its original box UP-OPENED.

1 Absorber, Shock
Stcok No. F36-01-00011
Dwg. No. 20-90-1
1 Chain
Stock No. F36-01-00201
Dwg. No. 20-18-29
Used on Watch, Pocket
Hamilton, R.R. Grade

Would this shock absorber and chain been used on this watch as well. I belive both the 4992b and this A8 are both 16 size watches.

Hi Michael. Your A-8 is in really nice unused condition. The engraving on the back of these is not very deep and on the ones that were used it is often not very crisp. On some of the more heavily used ones you typically have to tilt it under a bright light to be able to see the markings. Having the original box is a real plus in many ways, especially for collectors who seek examples in as close to mint condition as possible.

These A-8s were used in all kinds of aircraft for the purpose of determining how fast you were going, and that was essential to determining when you would arrive to where ever you were going. That is also useful information for many other things including knowing if you have enough fuel or if you have to stop along the way.

Aircraft of the day would have an airspeed instrument on the panel but this does not tell you how fast you are going relative to the ground. It only tells you how fast you are going relative to the air you are flying in. Think of it this way - you are in a transport aircraft and your airspeed instrument says you are travelling at 100 miles an hour, but you are flying into a wind that is blowing the opposite direction at 50 miles an hour, how far will you go in one hour? The answer is 50 miles. The reason is for every mile you fly through the air, the wind is pushing you back a half mile through the air. Or if you have a tail wind of 50 miles an hour - a wind that is blowing in the same direction you are flying - and you are flying through the air at 100 miles an hour, how far will you go in one hour? The answer is 150 miles since the wind is pushing you forward 50 miles through the air every hour in addition to the speed your engines are moving you forward 100 miles every hour. There is a big difference if you are traveling a ground distance of 50 miles and hour and 150 miles an hour and it is important information to a pilot or navigator. It gets more complicated when the wind is coming at you from some other direction that directly in front or directly behind you and you need to use trigonometry, but you get the idea.

Anyway, there you are in your airplane flying along and you know your airspeed instrument is telling you something but it is not terribly useful information by itself. One easy way to find out how fast you are actually traveling in terms of distance along the ground is the following. First you get yourself a map to take with you there in the cockpit (they are called aeronautical charts), and then you find out exactly where on the map you are by looking around at the landmarks. Next you pick out two easily identifiable landmarks that you will be flying over - something like a road or a railroad track or a river or whatever, and ones that are a couple of miles apart, give or take. You then take out a ruler and measure the exact distance between those landmarks on your map and using the scale printed on the map you determine exactly how far apart those two landmarks are. You then fly over the first landmark and when you are directly over it you start your stopwatch. As soon as you pass directly over your second landmark you stop your stopwatch. You now have two measurements - how long it took you to fly from one point on the ground to a second point on the ground, and the exact distance between those two points. All it takes now is a simple calculation to give you your exact ground speed so long as you are flying on that exact compass heading, and so long as you do not fly so far or for so long a time that you get into a differnet wind pattern. You can also use this knowledge of your exact groundspeed to tell you whether to add or subtract to your airspeed instrument reading to help keep track of how fast you are going relative to the ground. You take groundspeed measurements with your A-8 and your map every so often as you are flying along the same heading, or imediately after you turn onto a new heading and voila, you are now doing some elementary navigating.

As to where these were used the answer is in pretty much any kind of aircraft. They were more commonly used on larger aircraft like transports, cargo planes, observation aircraft, and bombers, but there were also used in small aircraft like trainers, fighters, liaison aircraft, etc.

Since yours is crisp with the original box it would not have seen any use itself. The late date on the box further supports the thought that it is an unused example.

The price you paid is fair retail rather than a bargain for these but you did well since you got the original box with it so no worries.

Thank you very much Jim for the simple but informational explaination. When I posted this question I did not realize this question with the same watch had already been visited by this forum...for that I appologize. Would this watch been carried in some sort of container like an Adamson or would it have been carried around the neck for easier access. I would think putting this watch in an Adamson type case would be a pain due to having to depress the stop button when you have passed your landmark. I think most likely this might have been carried in a bumber in the pocket or around the neck on a cord. Any thoughts or comments anyone? Thanks again for the great information Jim. Mike

Also, I tend to see more Elgin examples of this timepiece. Is there any information, maybe in Whitney's, to which company made more? I can also imagine that Elgin and Waltham were not the only makers of this watch. Is that correct?

Normally they would have been carried in a pocket or sometimes they were clipped to a kneeboard in a simple metal springclip. A kneeboard is a small clipboard that has a strap. When you are seated in the aircraft you place it on your thigh above your knee and the strap goes around your leg to hold it in place. The you clip your aeronautical chart on this so you have it handy without having to use a hand to hold it.

By the way, another use for these in navigation was in combination with a bubble octant so you could find your way when you did not have and landmarks such as when you were over water or over land where you were at a high altitude or such when ground landmark use was not accurate. You would take a series of readings and average them out over the time you recorded on the A-8 stopwatch.

You could buy a WW II era kneeboard or bubble octant that still has its springsteel clips on it and mount your A-8 on it for a display.

These are not high quality timepieces like some of the chronometers and such so there would be no point in having a special case for one.

By the way, a nickname you sometimes hear for these is 'jitterbug' because they make such a loud racket when they are running - it sounds like of like a cicada when they are running.

Thank you Jim for another helpful explaination. Mike

Well Michael, as Jim has stated, "These watches were used for many different things in the military,"....I was in the Navy and was for a time a Training Instructor in the Navy Fire Fighting School located in Pearl Harbor, Hawaii.... Part of the training process included training the new guys just out of boot camp how to use an OBA, Oxygen Breathing Apparatus, and the timing was critical on the amount of time these new people could stay inside the burning building with the OBA in place....I would use one of these stop watches to monitor the time that the OBA was being used and it was critical to get the new guy out as quickly as possible after his allotted time had expired....They were never issued,(the watches) they were just part of the equipment being used by all the Trainers....

Just another use for your watch....

BTW, your watch is in very nice condition and I, for one, do not think you paid too much....No Sireee....

Regards,

Jerry

Thank you Jerry. It just goes to show a timer like this has many uses. It was nice to hear from you...I think for the first time. Nice conversing with you. Cheers, Mike

Thanks Michael, I appreciate your comment....

I read most of the posts in this Forum, however my experience level with Military Watches is very limited but my interest level is quite keen so I do find many of the posts very interesting....

You guys are doing a super job of maintaining interest in the Military Time Pieces and I for one appreciate it very much....

Thanks and keep up the great work....

Regards,

Jerry

I want to thank everybody for their replies & Questions. Responses like this keep the club together.
Patrick.

I found one of these A8 stopwatches at a night market in Thailand. I don't want to harm it. Would anyone know what would be the best way to open the back of the watch?

It unscrews

It must be the front unscrews because the back has a flap type hinge at the bottom. Thanks