PS Magazine Issue 056 1957 Series [56 ed.]

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Connie Sez-

Hey, There. •• You know, there are some guys around who just don't give a hoot how they spend their dough. Not that it's any skin off our noses, most times. But, there are times when these guys start throwing their bucks down the drain, they fll.!.sh some of our lo,ot, too. For example, toke these guys who start pulling cables off their vehicles when they show the slightest cracks. These ore the "spit·and-polishers"-the guys who think they'll make on impression on their inspectors by having every· l~ ~ thing absolutely one hundred per cent. ~.,' The things these guys are doing are just downright, down. cussed unauthorized. Para 9b of TM 9-2810 (Oct 53) makes 'em that way. It says there that as long as an as. sembiy or port has usable life left in it, that part o r assem_ bly's to stay on the vehicle. It's only when a part or assembly can flub a vehicle that you're suppose d to pull her and put another one .on. Further than that, it tells inspectors that they shouldn't expect a guy to replace a port while that part's still good, no matter how shlompy it might look. Here's what the words say-read 'em for yourself:

b sue No. 56

1957Serlel

Publisbtd by lbe Department of the Army for tho information of organizational maintenance and supply personnel. Di stribution is made through normal publication channels. Within limits of availability, older issues may be obtained direct from Preventive Maintenance Agency, Raritan Arsenal, Metuchen, New Jersey.

IN THIS ISSUE FEATURE ARTICLES Testing the 24-Volt Systems Ignition System Te sting Federal Supply Numbering System

2 17 29

Lens Tissue

42

Wheel Scraper Operation

52

DEPARTMENTS Connie Rodd Tank Talk Half-Most Armament Quartermaster Chemical Engineer Contributions Connie Rodd's Briefs

22 26 37 40

42 46

50 62 65 PS wants your ideas and contributions, and is glad to answer your Questions. Just write to: Set Half·Mast, ps. Raritan Arsenal, Metuchen, New Jersey. Names and ad· dresses are kept in confidence. The printing of this publication has been approved by the Director of the Bureau of the Budget (17 Apr 56). WO-HCH AL.LMeANS THAT AS L.ONGAS THOSe PART'S A"'e STIL.L. OPEi~TING OK, YOU L.EiAVEi 'EM Be. NOMATTEiR HOw THeY L.OOK. !3UT SOMe GUyS DON'T-AND TI4ATS WHAT w e SHOUL.D

131" TO'D Af3OUT.

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These tests will tell you juSt where your troubles are, and what units you must replace. There are several differenc ways in which you can hook up test equipment and make satisfactory tests of your vehicles. The tests listed below have been carefully worked Out and proved safe, easy and convenient. You can use them, or you can use the hookups devised in other systems. Either will be OK. But, for goshsakes, don't mix your drinks. If you use these tests, make 'em juSt exactly as they are laid down here and you will get good results and not louse up your equipment.

As you know, the using-unit mechanics are supposed to be able to check all the separate assemblies of the electrical system and decide which ones to leave on the truck and which ones to replace. The only water-proof unit you open up is the distributor, wb.ere you swap ignition points and condensers if needed.

These tests will tell you just where your troubles are, and what units you must replace. There are several different ways in which you can hook up test equipment and make satisfactory tests of your vehicles. The tests listed below have been carefully worked out and proved safe, easy and convenient. You can use them, or you can use the hookups devised in other systems. Either will be OK. But, for goshsakes, don't mix your drinks. If you use these tests, make 'em JUSt exactly as they are laid down here and you will get good results and not louse up your equipment.

As you know, the using-unit mechanics are supposed to be able to check all the separate assemblies of the electrical system and decide which ones to leave on the truck and which ones to replace. The only water-proof unit you open up is the distributor, where you swap ignition points and condensers if needed.

This 'ere new Model 129 Load Bank is the latest gadget to hit the secondechelon equipment. It lets you load up your generator to check the output, and it gives you a field rheostat to control your generator while testing it. To use it for this series of tests, you want to use the 24-volt terminal with all three links closed. And, of course, your regular tool kit. You'll get better results if the driver and the shop electrician team up to test the truck. 3

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This 'ere new Model 129 Load Bank is the latest gadget to hit the secondechelon equipment. It lets you load up your generator to check the output, and it gives you a field rheostat to control your generator while testing it. To use it for this series of tests, you want to use the 24-volt terminal with all three links closed. And, of course, your regular tool kit. You'll get better results if the driver and the shop electrician team up [Q test the truck. 3

Now connect the positive (+) lead from your low voltage circuit tester voltmeter to the positive (+) terminal of your second battery-the one the starter cable hooks to. Connect the negative (-) lead from the 50-volt terminal of the tester to the negative (-) post of the first battery-the one where the ground cable fastens. The best way to attach the leads to the battery posts is with a small sharp prod driven right into the post itself (it's made of lead). Tap gently so's not to bust things. If you haven't got such a prod, and can't make one, be extra sure your cable clamp is clean and tight on the battery post. Better take it off and be sure, and then put your voltmeter clips on the cable clamp tightening bolt -trouble is, you sometimes get a high resistance because of corrosion between the battery post and the cable clamp. When you make this connection, your voltmeter should show somewhere between 23 and 26 volts. All this means is that you have the meter connected right. 4

Now, crank your engine with the starter-for not more than ten secondswith the igntion switch off. If your voltage falls below I8-volts while you're doing this, replace the batteries. This test will show up any trouble inside the battery which didn't show up when you checked the specific gravity-things like plates busted loose from the terminals. Did you get at least 18 volts while the starter-'s cranking? OK, now shift your voltmeter positive lead over to the starter switch terminal, and the negative lead over to the vehicle frame and repeat the test.

If you still get within one volt of the voltage you got from the battery posts, and your total voltage is 18 or more, you are all right in the batteries and cable.

Caution: On these tests, if working with a helper, do not make a permanent hook up at both ends of the cable you are testing-fasten one end and then touch the other tight to the source of current but couch it in such a way that if you do have a real bad cable and the meter hand goes right off the scale, you can turn it loose instantly to prevent harm to the meter. If you are working alone, you'll

have to make all these checks twice, oncc with the voltmeter lead on the 50 volt tap to sec if you get more than one volt, and then again with the voltmeter lead on the I-volt scale to measure the voltage in tenths of a volt. Positive lead at the vehicle frame, negative lead on the first battery negative post. Thjs checks the ground cable.

Next, lead at the positive POSt of the first battery, negative lead at the negative ' post of the second bauery. This checks the link cable between the batteries.

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'Then, positive lead on the positive post of the second battery, negative lead on the starter switch terminal. This checks the bauery.to-starter cable.

In anyone of these tests, does the voltmeter show over 5/ 10 of a volt with the starter cranking? If it does, remove the cable, clean and inspect, clean the battery posts and re-install-tight. Then retest. If the voltage drop is still there, replace the cable and again re-test. When all this checks out, you're sure of your baueries and cables-and no system will work without 'em. Now you're ready to test the charging circuit. 6

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6e=-T OF T$TG t-IA? 6f%EN WHICH WILL C~ECK

WOFl~ED OUT

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