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Mainly for Oldtop, but Roy and some others may shed some light:

I'm trying to get a handle on what it was that made top-loading air filters less satisfactory than side loaders apart from convenience/access, if anything. That is, were they less efficient or just less likely to receive attention? I've crewed vehicles (M48A2, M60A1, M60A2) with both systems, but only at Ft. Knox which isn't as dusty as some other locations that come to mind.

Also, I notice that some of the top loaders on M60A1's have a smooth-sided armored box on the outward side while others have a single horizontal "ridge" there, like on this one:
image2.sina.com.cn/jc/...093650.jpg

...my pics of the M60A1 side-skirt test vehicle, "Hotpants", has this ridge too. I don't recall any function associated with it.

Thanks!
D.

Hi Doug, all,

The top loading air cleaners were made of steel, rather than aluminum as the originals were. I recall that our maintenance guys didn't like the side loaders because the mechanisms were easily damaged, hard to repair, and the filter elements were often screwed up by crews trying to jam them back in. The doors were tricky and the seals often leaked, which is a problem when they are sucking air in that close to the tracks! The doors were a problem from the beginning, and the horizontal rib your pic shows is a reinforcment to stiffen the door and keep from flexing. (Yup, that's a side loader in your pic.)

I remember fighting with both, and hated the side loaders. The filter element was a very tight fit, and had to be held at just the right angle. However, you had to stand beside the tank and hold the heavy element at roughly shoulder-height to do this, which made it double hard. We usually used two folks to do it, one on the ground and one on the tank (leaning over the side) to guide it into the slots. The top loaders were a piece of cake, and the element just dropped into it's cradle.

Sometime after the A1s began to be produced, fairly early in the run, they changed to the top loading 'armored' type. I remember hearing that this was originally done by the Israelis, and adopted by us. But there are/were some A1s with the old-style side-loaders. The RISE modifications were supposed to replace these, when they were done.

This is all from deep memory, so I await corrections from better memories!

C

Thanks, Chuck...

Only now, I'm really confused! I based my phrasing on "Oldtops" comment in the other thread:

One indecater that this is an first production is "side loader " air filter housing which is the same as on the M48A3 upgrade, M60A1s picker up the "top loader" armored box type...and with which the vehicle was damned for its operation life.

...which I understood (perhaps incorrectly) to mean that the toploaders were the troublesome types.

As I didn't personally experience problems with either, I'm just trying to clarify in my mind which system was preferred, and why. Sounds like you're more a fan of the toploaders.

Cheers!
D.

The first problem with top loaders was they stood out and everything fired at the tank hit them, 10 micorms (I could put that much dirt in your eye and you wouldn't notice it)of dust would kill the 1790 diesel engine.
The side loaders were postive sealing (when the cover was closed it was sealed) . The top loaders lid had two legs (one on each side) that engaed two studs on each side of air filter cage, when the lid close it was desiged for the leg to force the element (cage) seal into the front of the aircleaner housing so that no unfiltered air could be drawn into the engine intake..or all air had to go through the filter element first. The filter elements were a group of bag shaped cloth or paper envelopes held in a welded steel cage with a rubber gasget on the open end.
Problem #1 Each manufacter placed the metal studs a little bit off from what the specs called for, so when you closed the lid the leg may or may not engae the two studs and complete seal.
Problem#2 It was possible for the crewmen to put the element in backwards and by standing on the lid get the bolt holes to line up enough to get the bolts in...results were raw unfiltered air in the engine.
Problem #3 The soution was to weld shims to the lid legs to make sure they made contacted with the studs on the element cage. To do this the instuction for testing the seal was to coat the element seal with art white lead oil paint close and bolt down the lid then unbolt it and open the lid and check to see if there was a complet impression from the seal on the end of the housing...."However" because each manufacter place the studs differantly if you had welded shims the seal could end up too tight and the gasget seal was crushed and no airtight seal..raw unfiltered air (again).
My solution was to glue plastic shim or ring cut from PVC pipe on the studs, that way the ring would crush before the seal did and I knew we had a good seal no matter what...ya it worked fine!
As for the crewmen you simply put alining makes on the filter elements and the housing and hopefully the dummys would get it right..maybe.
...sub-problem err lets call it 3A problem, on thr front of each filter housing was a elbow that conducted the filtered air to the engine intake, the problem was the 3/8" capscrews holding it to the filter housing would work lose (even with lock washers) and you had (again) raw unfiltered air getting into the engine. the solution was to go to 1/2 capscrews and a spring washer...well it worked for me.
sub-problem 3B...the cloth elements were which designed to be cleaned and reinstalled, these elements developed holes in them and the only way to detected them was to build a "ligt box" over which you placed the elements (in a dark room), as you found each hole you placed a drop of "Elmer's glue on it. This problem alone killed over 50% of the dead lined engines, the solution was to use paper "one time" uses filter element which were in such a short supply that they'er production never caught up with the needs....so tank units clean and patched the paper elements and reused them...raw air problem again!!!

Hi Folks!

Thanks Top for explaining your post. I guess that one is a case of the repairer's point of veiw.

I was like Doug(SORRY DOUG). While I didn't work directly with the M60s very much, I never heard any of the tankers I was around saying the top loaders were a problem. For the most part, all of them loved the top loading design. But then maybe it was a major case of they didn't know their last engine failure was caused by raw air intake.

That's two things I have learned today!
Sgt, Scouts Out!

- Roy_A_Lingle

I was like Dong.

Hi everyone,
My experience was with top loaders only, which came in armored and aluminum. Aluminum was on some of the A1's we had in 1-63 Fort Riley. The only side loaders I had any dealings with was when the Kansas National Gaurd had straight 60's and would be on the the range. The crews hated them. They wanted the simplicity of the top loader. Never had a problem getting filters either, got new ones every Q-service. I remember having to check the seals on ours too with that paint Ole Top talks about. They all sealed fine, this was in Germany, Riley and Irwin. The filters where made by Donaldson (?) from what I remember. If there was a sealing problem it would've been very evident at Irwin. I think the biggest improvement was the VDSS system, which IIRC stood for Vehicle Dust Scavenge System. It got rid of the blower motors and could self clean the filters. We had that system at Irwin. Even had a warning light in the drivers compartment. I absolutely loved that system. As far as placing a filter in wrong, yes, it could be done but you had to be a rock with lips to not notice it was when you closed the lid. To me the top loader was the way to go, and for what it's worth, blowing a pack was not a common thing, even with all the miles we drove in Germany. I guess my comparisons are also skewed by my very negative experiences with the M1 system and it's very high sensitivity to dust.
I am still trying to figure how the side loaders were less of a target than the top loaders on the 60, Both are loacated in the same place and took up the same amount of space. At least the later model top loader was armored and not aluminum.

My perspective

Joe D

I am still trying to figure how the side loaders were less of a target than the top loaders on the 60, Both are loacated in the same place and took up the same amount of space. At least the later model top loader was armored and not aluminum.

I might be wrong about this, but I think Oldtop was not referring to "hostile fire" when referring to what "might be fired at them", but dirt, debris, dust and the like. I'm sure he'll correct me if I'm wrong 'bout 'dat.

Well, what's emerging here is at least a good explanation of why I was confused...it seems there are at least two bodies of opinion out there regarding air filters, and maybe some of that follows the perspective of crews vs. mechanics or something. For sure there's a basis of experience to support both views.

My own one was that there was no significant difference between the two types...each having it's own virtues and vices. But I've heard strong negative opinions expressed about the toploader before and didn't fully understand the reason for it. I'm not sure I do now, but at least there's something to go on.

I'd sure like to hear any other opinions from those with time on either or both types.

Hi Doug, Roy, Oletop, everyone!

I'm guessing that which one you hated more depended on which one gave you the most problems.

I remember our maintenance guys being very firm about putting the air filters in right, so Oletop's comments probably cover the same concerns. I remember the effort that was required to get the lids closed on the top-loaders, and how careful we had to be to get them right.

One needed and welcome improvement on the M60A3s were restriction indicators on the intake elbows...as long as no one knocked them off. They were vacuum indicators, similar to those used on many commercial diesels, that told you it was time to change/clean your filters.

I do know that the maintenance guys didn't have much nice to say about the side loaders, especially the doors. Apparently, they were subject to warpage under some conditions, which broke the seals on the filters. Fixing the doors was quite challenging, and being aluminum they were virtually impossible to weld under field conditions. The latch handle was held shut by a steel bolt, tapped into the aluminum housing. Inevitably, some young, strapping, not-so-bright crewman would overtighten the bolt and strip the hole. At some point, there were no practical bolts available large enough to retap the hole again, and the entire housing had to be replaced (or the hole had to be welded up...cheaper and simpler, but not likely). Being in a Reserve unit in the early 80's,parts were slow coming, and a simple stupid repair like that could deadline a tank for months or more.

C

What was the compounded problem was due to dust ingestion (both filters and lose elbows) there was a shortage of engines (RISE mod) at the same time a batch of "bad" pistions got into the system so maint units were caught between a rock and a hard place as were rebuild centers, you would see engines with mixed parts (RISE and non-RISE mixed). Once the new air filtering system was in place on the production line most of the problems were ironed out.....but from 1975 to 80 maints was pure hell in the support units. As for this thing between the side loaders vs top loaders, just look at the hight deference, the Israeli IDF pointed out time after time the damage done to the housing in combat...why in the world would you desgne a vehicle with its air filtering system sitting out in the open on the fenders?????

This story begins with the M48s. Like most med to heavy tanks they are limited by their range of operation, if one reads the manuals you'll the range of U.S. diesel powered tanks is around 300 miles. However this was not the story with the gasoline fueled models, M48s and A1s were lucky if they got 90 miles per fuel load. (the german Tiger 1 had a ture combat range of 70 to 80 plus miles) The Army tried fuel injected engines for a few more miles, I know there are pictures foating around of M48s with barrels of gas strapped to a rack on their ass to push for more range (made the hairs stand up on the back of my neck just to think about it)...So heres the rule of thumb I use in calulating the fuel needed to support a tracked vehicle in the field. For every hour of cross-country operation you lose 5% of your total road range on top of you normal fuel consumtion...or a addistional 50% of your total road range milage every 10 hours...or if you burn half your fuel in 10 hours cross contry move you'er out of the go go stuff. This was the wall every army in the world was up against..and still is. So what has this to do with airfilters you ask. Well when the U.S. went to the dieselized M60 they remove the "lil joe" (APU) and installed form -fitting fuel tanks in the engine compartment, one other thing had been removed, the aircleaners which has sat in the left and right front of the engine compartment (fuel injected M48s had been the first with airfilters moved in this manner ). Now we had a med tank with a 300 mile road range and better than 150 mile cross country range (the diesel powered M103 heavy tank could now get better than 100 miles per fuel load with twice the fuel tankage)...However we now had the airfilter housings sitting rightt out in the open for everybody to shoot at, it was like the designers had said "oh were should we put these things")

"I do know that the maintenance guys didn't have much nice to say about the side loaders, especially the doors. Apparently, they were subject to warpage under some conditions, which broke the seals on the filters. Fixing the doors was quite challenging, and being aluminum they were virtually impossible to weld under field conditions. The latch handle was held shut by a steel bolt, tapped into the aluminum housing. Inevitably, some young, strapping, not-so-bright crewman would overtighten the bolt and strip the hole. At some point, there were no practical bolts available large enough to retap the hole again, and the entire housing had to be replaced (or the hole had to be welded up...cheaper and simpler, but not likely). Being in a Reserve unit in the early 80's,parts were slow coming, and a simple stupid repair like that could deadline a tank for months or more."
I was lucky enough to have a LM-62 welding unit with a "mig" system so I could rework the housings, once the word got out that I was repairing the housings I had Army reserve and NG units bring them to my shop for repair. With gobs of money for the Marine Reserves as well as pro welders I had a first class welding and machine shop, I mean my reserve troops built ships and powerplants for a living so they did great work.

Hi Folks!

I always though that putting the air filters out on the fender was a compromise for some reason. Never realized it was to make room for larger fuel tanks.

One thing I have learned from this, which surpised me, was the fact that the side loading boxes where made out of aluminum.

Now that is a weight compromise and I guess the IDF proved that it wasn't worth it. If I understand it right, they were the ones who came up with the armored version?

I think this is a major example of everything that goes into a tank is a compromise with something else. Only combat proves if each compromise is a good or bad idea.

Thanks Top!
Sgt, Scouts Out!

- oldtop

What was the compounded problem was due to dust ingestion (both filters and lose elbows) there was a shortage of engines (RISE mod) at the same time a batch of "bad" pistions got into the system so maint units were caught between a rock and a hard place as were rebuild centers, you would see engines with mixed parts (RISE and non-RISE mixed). Once the new air filtering system was in place on the production line most of the problems were ironed out.....but from 1975 to 80 maints was pure hell in the support units.

This at least partially explains my lack of familiarity with this problem in spite of the fact that I crewed side loader and top loader vehicles. All my experience was prior to 1974, so RISE parts availability was not an issue. Furthermore, I ETS'd about 60 days after the October (Yom Kippur) war, so any lessons learned by the Israelis during that one (apart from vulnerability to TOW missiles and the shortcomings of committing tanks without infantry support) were too late in coming to reach me. I'd moved on to other things.

I was also probably a bit spoiled by serving my last ~2 years at the Armor Board, one of the most support-rich units in all of tank-dom.

The Israelis got a way with "cheating" for years (sending tanks in with out grunt support) till Yom Kippur..after all, the enemy had always ran away before! Any 2nd Lt in any other army knew you don't do that!!!
Know one ever want to fes up to how bad the M60 engine shortage was in the Marines, I had M60s sitting for over a year on my maint line/bone yard deadlined due to the lack of engines. And I couldn't get the parts to rebuild.