Prior to a Rock Drill with the Division Commander I was walking some younger troops through it. Talking them through the maneuvers I said "the tank will go to this position and the tank will go bang!, then move to this position and the tank will go bang! I didn't know the Division Commander was walking behind me when he tapped me on the shoulder and told me I had it all wrong. He said, "Sergeant the tank will move to this position and the tank will go BOOM!" Two lessons learned that day. Tanks go BOOM not bang and when your troops seem unusually attentive check your six.
22:25 Idk if I am wrong about this, but I think one of the reasons why the Sherman tank (and other similar tanks) was so tall, was, because of the transmission shaft
Not entirely wrong. The other reason was that the Grant/Lee/Sherman all used an aircraft radial engine, so the crankshaft was in the center of the engine instead of at the bottom like a Panzer 4. That made the driveshaft much higher, which made the bottom of the turret basket much higher.
Don't the blow off panels also protect the crew from detonation of the rounds if they get hit or catch on fire? Pretty sure the ammo is behind a blast door so that if they go off they will blow out the blow off panels instead of blowing up the crew compartment - if they were also going to be used for fast resupply, I can see that - and OF COURSE they didn't buy the support equipment to make that happen, it was the first thing to go when the costs exceed budget.
Can you please explain what exactly are the advantages and disadvantages of front vs rear transmission? I have been looking for this for ages and a lot off reasons i found makes no sense because people compare to much to (race)cars. For example people cite weight balance as a pro for front transmission, (saying it helps to have weight in the front wich actually seems weird for trench crossing) while i believe you can alter the center off gravity more with the location off the turret (wich is usualy more to the back with a front transmission)
Another example is height off the tank because off the drive shaft. While it clearly does make a tank higher in for example a sherman, you can also see that the driveshaft could have been made lower(if they used 2 more universal joints or a set of gears) or just move the driveshaft to one side off the tank, wich would make the problem less pronounced. This off course would make the drive train a little bit more complicated but not a huge deal actually. So clearly it didn't bother the designers to much.
@@therogueadmiral only the sheman would roar, the M1 howls and post Vietnam war IFVs like the Bradley are generally far quieter than they have any right to be for their size... especially from the front! (Personal experience of beeing chased down by CV9040s and a CV90 ARV on several occations.... on foot. ) You feel them through the ground long before you hear them, and you can't ident the direction they come from by the feeling alone...
@@brianreddeman951 It is very unprofessional if the presentation is followed with models or pictures pointed with a finger. BTW. Polish/Czech APC was called SKOT. While "S" stands for "Sredni" - a medium sized, it was one of the biggest if not the biggest APC of its time. OT-64 was a Czech name for it but both were in use in two countries. SKOT was was a very modern vehicle in the middle of '70s. Almost all (weak armor, weakly armed)of today's designing standards SKOT filled 50 years ago. Apart from the crew of 2 or 3 men, SKOT was able to take 10 soldiers onboard.
That bit about the compensation for the fin stabilized rounds was really interesting. I never really thought about it, so I would have answered wrong. After hearing you explain it, it makes all the sense in the world. That was super cool, thank you. I really enjoyed that, along with everything else.
A similar thing happens with an RPG, specifically with the PG-7V rocket, in that it ends up turning _into_ the wind. I think the mechanism is a little different, since there aren't really any substantial fins on the rocket I think it might have something to do with a lift force being produced when the air moves sideways across the round body. It tends to make an already inaccurate weapon even worse.
@@Laotzu.Goldbug rpg rounds do have fins which extend once the rocket leaves the barrel, they run a substantial length of the narrow rocket part, thus very highly affected by wind.
It really doesn't make sense though, because there is no forward acceleration on the round once it leaves the gun tube. The round is not a rocket. Therefore, any yaw of the round should not have an effect of the direction of the velocity of the round, all forward force has already been applied. This phenomenon only makes sense when the projectile still has forward acceleration after being affected by the wind, such as an RPG rocket. I wonder if there is more to this explanation.
@@hjalmar4565 Maybe think about the physics before just saying I'm wrong. Ignoring air resistance, rotating an object while its traveling with 0 acceleration will not result in a change in the direction that object is traveling. So there has to be some other force acting on these shells other than what the Chieftain stated, or perhaps he got it wrong. No one is 100% right 100% of the time.
Can you give us a watered down, wont get in trouble with the Army version of how armored operations work? How you go about going outside to do tank stuff, how doing tank stuff works, maintenance, resupply, going back for the next guys to go out and do tank stuff, etc. Aircraft get a mission, sortie, and then come home, but ships are out for months at a time doing things. I imagine tank stuff is somewhere in between the two?
"Aircraft get a mission, sortie, and then come home, but ships are out for months at a time doing things." At one point the Air Force wanted nuclear-powered bombers that would orbit the North Atlantic for weeks on end. I imagine serving on one of those would be like a submarine crew, except with windows, but all you see is clouds and the ocean surface.
Drivers have it best far as where to sleep ( now days that is) in a Bradley you just pull a lever and the back rest drops . Use whatever to get it at the angle you want and sleep. To drive all you do is sit up, pull up the backrest , done. Good vid.
Not a a"bullet" it is a cannon round. There is no bullet in that object he is holding. A bullet is a solid projectile fired by small arms. It is the part of a cartridge that actually leaves the gun to fly to the target. A cartridge or 'round' is a bullet and propellant case and primer assembled in a unit (what ignorant people and the media call a "bullet"). That is a 30mm cannon cartridge, with a shell instead of a bullet, casing and primer. No bullets involved.
One thing to keep in mind about muzzle brakes is that they are somewhat dependent on the mass of gas relative to the mass of the bullet. Putting a brake on a .38 Special (relatively small powder charge, low pressure, big bullet, especially in the original 200grain loading) would make little difference in recoil. Putting a brake on a 5.56x45 with the 55grain loading makes a much bigger difference because there's much more mass of gas (at higher pressure) to operate against the brake.
Only to receive concussions from the main gun being fired. Other than canister, the Abrams doesn't have a low pressure round. I think I heard something about the new multi fuse round being less terrible. You'd think after nearly a decade of insurgent warfare, we'd make some minor changes to actually make tanks useful.
24:30 also having the engine at the front means that anything that does make it thru the Armour at the front still has to get thru an engine block before it hurts you not great for the engine tho... :P
Probably the most common question I get asked about tanks is how do you get power from the hull to the turret since the turret spins. I know they use a variation of a slip ring but explaing about powered rails and brushes tends to make peoples eyes cross. Maybe you could do a video and explain it better.
The Tank museum at Bovinton recent series "the Matilda Diaries" shows a teardown of the turret rotary joint with combined electrical & hydraulic layers, in the turret electrical systems video with clear explainer and excellent video work. A good, simple 1938 design example that's easily comprehensible. Probably better than nick could, due to pro editing team and their resources on hand. His commentary on the video with David Fletcher would be great tho, especially if linked to his own Matilda review some time ago.🙂
Sadly while the Chieftain always talks about track tension WG is putting their hands in their ears and going "LaLaLaLa I can't hear you, tensionless tracks look kool" (tvp vtu is just one example)
Grandpa remembers saving French soldiers with OT-64 who were stuck in some fire engagement in Kosovo (KFOR mission). There was a narrow, muddy road. Driver had to back up several hundred metres, because the risk getting stuck/fired at when turning around was high. They came in, loaded Frenchies and got away.
@John Fulghieri-- DU is a lot less radioactive than NU, but U235 accounts for only a very small fraction of the radioactivity of natural uranium. The rest comes about equally from the U238 and its decay product, U234. The latter gets swept out during the enrichment process, along with the U235.
Donald Palmrose is correct. Also found in an M1 Abrams is : Thorium oxide in combustor liner in the turbine engine. DU (Depleted Uranium) ammo M829 series DU APFSDS-T. DU in the armor of M1A1 "Heavies" and M1A2 , identified with a U at the end of the serial number. A thermal imaging window "may" contain thorium- not sure if this is specific to an Abrams though. Self-luminescent sights, dials gauges probably contain radioactive material. Source: Radiological Sources of Potential Exposure and/or Contamination TG-238 U.S. Army Center for Health Promotion and Preventive Medicine 10 December, 1999
Here is a list of the best WW2 original content creator I've found Tank and AFV News, TIK, both Military History Visualized channels, Bismark aka Aviation history, The World War Two channel in real time, The_Cheiftain, Montemeyer, Forgotten Weapons, Bovington Tank Museum channel, Greg's Planes and Automobiles, the Stalingrad Battle Data, Mark Felton Productions, Armchair Historian are the best of the best. Please copy, paste, share this and update if I've missed some.
I think that we need at least one video showing off The Chieftain's new house, or at least his office. It could be called "Inside the Chieftain's lair". We also need an Inside the Chieftain's Hatch video of your desk at your NG job. It's rare that people actually get to see the inner workings of an actual tactical military desk. :D
That's a nice and educational way to show off your models :) thanks for another great vid. I agree - building scale models is a fun way to get more familiar with the different parts of a tank. I highly appreciate companies like Tamiya who take the time to label the parts in the construction manual. It's also a good excuse for me to look up both technical drawings and photos of the tank to make sure that all the details are there, and do a bit of research on the history of the vehicle and the experience of its crew. I always make it a point t learn something about the tank and its crews whenever I finish a model.
That is obviously larger than a 20mm. Looks like a 30mm. A 20mm isnt that much bigger than a .50, and usually has a larger length/width ratio. That and the standard 20mm case in the west is 20x110mm which has a much longer case relative to the round. That thing is way too short and thick, and it has almost no neck.
Did I just hear a Ballistic Meteorology class in the middle of the video? I did! And I just thought the Red Legs was only ones who knew that. I guess tankers learned it too! Man I miss Field Artillery.
Heh! I did my compulsory service training as a radio specialist in a 120mm mortar platoon of a mechanised batallion, and if there is one unit especially dependant on accurate meterology, it's the batallion level heavy mortars...
I was curious in the movie "Fury" ,after they hit the land mine ,they started to repair the track but never addressed why they didn't complete the job.
If I remember the movie correctly there really wasn’t enough time for a repair like that, I think the bogey was messed up too. There were Germans coming down the road
Which way do you aim the dart? (I paused the video, scouts honor) You aim the dart downwind. The fins are blown, causing the dart to "weathercock" or slightly tilt upwind. Like a model rocket.
huh i always assumed you would sleep under the tank or did a shallow trench and drive the tank over it ? actually couldn't you just carry a canvas tarp attached to one side of the hull or turreted rolled up wit a pair of poles? and then to set up all you need do is park up unroll the canvas tarp prop it up with a pole in each corner and voila you have a ready made tent ... make the poles of a decent size and strength and you can sling some hammocks between them and the tank...
You could, but why do that if you can spin the turret so that the gun is over the back deck, and it makes a ‘spine’ for the tent made by draping the tent o er the gun tube tothe deck edges? Still no mud.
Right now that might not be that easy to set up, as he'd have to ask one of the militaries operating them or KMW if he could get access to one of them for filming, as none are currently on display in museums.
'Glacis' is from military engineering and pronounced 'gla-see'. Pronounced thus being a French word. BTW sabot is French for shoe (made of wood) and is pronounced 'sabb-oh' not 'say-boh'. Thus you get 'sabotage' from cross French workers protesting by throwing their wooden shoes into their machinery. Infantry don't like muzzle brakes or blast deflectors on 'friendly' tanks as the blast gets directed to do unpleasant things to the PBI either directly with blast or by bouncing the local scenery off them. There are few pecetime character building moments to match approaching a stationary 70 ton mobile thing which can instantly begin moving at you backwards and does not know you are there until you have actually opened and licked up the exterior telephone and got the warm dry sleepy/busy inhabitants to acknowledge they have friendly human almost touching their tracks.
Enjoyable, for sight/gun alignment would you consider similarly detailing say Sherman and Pershing. Just read 740 tank battalions with mixed 76mm and 75mm Sherman after action report 1945, very sobering. “9th April 1945 At G178708 Lt. Loopey (3rd Plat) destroyed two 70-ton Jadtiger tanks w/128mm guns. At ,elschen Ennest the Pl4,t set up road blocks and remained for the night”. In February 1945 they claimed a Tiger 1 confirmed by the infantry support. Worth a read it does appear they alone destroyed 3 tiger vehicles.
It’s interesting to think how long it took to get some design rules down like: put the engine in its own compartment, put ammo in its own compartment, evacuate the smoke from gun after firing, thermally balance the gun, etc etc.
remember that many of these issues only got solved when they became a problem. before ww2 most tank guns were small and did not produce a lot of propellent smoke and that even in ww2 most tank engagements were at short ranges.
@@ineednochannelyoutube5384 And God forbid the bananas! (No idea if bananas or dried bananas are in military food but if you know about how radioactive bananas are you'll get the joke)
Bustle--'female version of the codpiece or something...' HA! :D I wish you had gone into 'track pitch'; I'm not clear on that. Also, would you do a video comparing & contrasting all-rear drive train vs front tranny?
@@TheChieftainsHatch Thanks. Given how 'pitch' is so often used in reference to angles, I was having a hard time visualizing how it applied to track. In fact, I was trying to apply it to the angle from roadwheels to the drive or front wheels. :p
At least the codpiece could dispense wine. If you tried to store snacks in a bustle, nobody would eat them, cause they would have been fumigated with 19th century lady-farts.
It is indeed the OT-64, more precisely the OT-64 SKOT with SKOT being either Střední Kolový Obrněný Transportér or Średni Kołowy Opancerzony Transporter, which means medium wheeled armoured transporter.
I vaguely remember bore sighting the M109 back in my Army Guard days. Later I learned to color inside the lines, went active duty Air Force and flushed most of that artillery stuff out of my noggin'.
Chieftain... when measuring wear on the barrel, is each type of ammo fire measured differently or or is it just a matter of how many rds fired regardless of ammo type? Or does the tanks record all this data automatically?
The description of aiming off away from the wind intrigues me. I've been competing at national and international level in archery for over 15 years, and we too use a fin-stabilised projectile. But we have to aim into the wind, sometimes by 1m or more over a 70m shot. You can see the arrow in flight, and the tail definitely gets pushed, but there isn't a subsequent "lift" back into the wind. I suspect it has to do with the extreme speed and mass of a sabot round, but if anyone has further information that would be very welcome.
Interesting. There are folks commenting elsewhere in this section that RPGs also have to aim with the wind rather than into it, so it’s more than just speed, at least.
It could be the strength/elasticity of the projectile. Arrows are flexible and won’t be affected by the crosswind pushing against the fin as much as a rigid sabot round.
This is clearly bugging me. I found this (www.aircav.com/cobra/ballistic.html) where 3.C.(3) states the effect you described for a rocket under acceleration. Which makes sense, because you have something propelling it at its new angle of attack. Since this (and every other source I can find) states such effects cease when the motor is turned off, I'm guessing that the fins and penetrator body are creating lift against the wind.
Interesting thought, and indeed when you watch high speed footage of arrows (check out the Werner Beiter stuff like ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-wGNslUNBrEM.html) you can see this in action.
That first link seems to indicate that it's a component of the launching platform's characteristics, and the bit you are referencing is launching when the helicopter out of trim. (i.e. it both requires additional, uneven control inputs, and is moving at a cross path to the wind), possibly because the wind will affect different parts of the rocket at different times as it leaves both the tube and the downdraft of the blades. At the very end of the paragraph, it simply states that if the aircraft is in trim, to aim with the wind, as the rocket will turn into it with no additional qualifications.
M1 bustle = Female cod-piece, Best line ever! That was hysterically brilliant. ~_^ As a retired SFC senior service school instructor I taught M1 Turret/Fire Control repair DS/GS at Vilseck, Germany 7th Army Training Command and USAOC&S APG Maryland. It never gets easier trying to explain the basics, great video.
Be me. Graduate Tank school yesterday. Get sent to Ft.Bliss with 100 other privates from my company. Learn that they are converting Stryker brigades to Heavy brigades. Gets sent to 1-36 IN. “Cool where are are the tanks”. there are none. “When are they coming”. December. “Ok thats fi...” .2020. wut. “What the fuck do I work on then?”. We dont know, guess you’re infantry now.
SKOT is Czechoslovakian, but we used to use it in Poland. Rather got poor reputacion, because it was used by goverment of PRL during military state in 80's. Yep, due to covid-19 situation I have a lot of time to watch missed videos ;)
This would’ve been improved by closeups as you talked. Even a iPhone’s macro lens would be enough. Just a suggestion. Love the video and pretty much all the content you create. (I’m even tempted to try the game, which is much of the point. Oh, capitalism, you cad!) Thanks!
There's a misunderstanding of "muzzle break" and "muzzle brake" and they're two different things. For example the D30 soviet has come with both, the earlier towed version had a "brake" which used a series of flutes to spray the muzzle flash back and to the sides and the export version had a brake version that directed a large proportion of the gasses simply TO the sides to reduce the length of the plume. In the case of artillery you want as little as possible of the BRIGHT FLAMING GASES shooting high into the air with each shot, a device that peels these gasses off is a *break* and will have as broad an opening on each side as possible with as small a final path hole as can be gotten away with. Muzzle brakes on the other hand are designed to keep the high velocity flow of gasses but turn and deflect them backwards, as seen on guns like the M230 30mm chain gun. The confusion is fun and simple. Same sound different words and different purposes. So people use the term "flash hider" instead for muzzle breaks. They don't actually hide the flash very well on small arms but they DO keep it from being a big long spew from a ball of light. Since the two purposes are often needed on larger caliber weapons we result with a great deal of confusion. But the true flash hiders are the cones on weapons like a Bofors 40mm or a DP28.
Nice idea about a video! The first thing I noticed was it would have complemented the layout if you brought the vehicle models closer to the camera! Some questions: 1. Can a blast deflector and muzzle break both be present on the end of the same barrel? 2. Can a muzzle break's exhaust paths be directed upward to lessen the ground dust effect? 3. Which guns and tanks have so much recoil that a muzzle break becomes pointless? 4. Can flames from a blast deflector ignite surrounding materials?
Some answers: 1. Yes, one muzzle device can do/be both, it can both redirect gas and flash away from the ground/shooter/optics and reduce recoil, but not all do. 2. Yes and many do, you see this in small arms a lot because they have significantly less concussive force to deal with so it's easier, but a well designed one absolutely can on a tank too. 3. I'm not sure about this one, couldn't say a specific model it applies to, but I'm sure that there are instances of a big enough gun on a light enough tank that the reduction in recoil while still theoretically doing something, wouldn't be noticeable. I wouldn't say there's a hard line though, any well designed brake will reduce concussion by some amount, and any reduction will reduce vibration and wear on the gun/optics. 4. Not easily, definitely not gonna catch brush on fire or whatever. In regular small arms it's very unlikely, even with guns that have significant muzzle flash, a flammable gas or liquid isn't likely to light even. Mythbusters tried natural gas flooded into an enclosed space and guns wouldn't light it. Now a tank has a MUCH bigger flash, but I think unless there was large amounts of still burning powder exiting the barrel (which would not be normal or good) I don't think a tank cannon would be much different, just a lot bigger. Hope that helps. (disclaimer: I don't drive tanks for a living and only some of this is from first hand experience, the rest is internet research and semi-educated guesses lol)
Thanks for the answers! Although I'd still like to see Nicholas' responses on these. Nonetheless feel free to join in like you did so! I'm just interested in tank gun mechanics, not handheld firearms. A few more mysteries: 5. Can engine exhaust smoke be toggle redirected under the tank for further concealment? Is it worth it? Has it been done yet? Does it hinder amphibious designs? 6. How difficult is it to manufacture depleted uranium for countries to make special APFSDS and hard armor plating? What infrastructure is needed and any international laws? 7. Why aren't ATGM launchers ever mounted behind the chassis of the tank facing upwards in a 45 degree angle? Aiming for a starting launch then a forward facing cruise. 8. Are shot traps still relevant in this day and age on decently armored MBTs? Leo 2A5-2A7+ turret front looks rather trippy...
@@rudolphantler6309 You're welcome. Yeah my area of "expertise" is basically just small arms, my interest in tanks is purely for fun, but they do share a lot on the conceptual, design, optics, and physics side so sometimes I know what he's talking about lol. I got nothin' for your new questions lol, hopefully Chieftain can help!
Thanks for the insight Kneon. 4. What makes range control officers pissy? The vegetation ignition, the direct fire, or the rubber sheet shenanigans? 8. What about the Leo 2A5-2A7+? Are we looking at the same thing there? Why was it made this way? And a new question: 9. How common is direct fire with artillery? Is it done with the same muzzle velocity or power in today's time as indirect fire? What situation brings it about and why isn't it utilized more to build more common awareness of the action?
Is there Merkava episode in the works? Will You make an episode where you will compare all type of suspensions used on the thanks? I am especially curious about all types of bogie suspension HVSS, Horstmann and one planned for German Entwicklung series
Isn't depleted uranium in shells and armor radioactive? It might have shielding but still..? Also, I would think all the settings, adjustments, and calibration would be computerized and automated by now. I guess most tanks aren't completely up to date with technology yet.
"supposedly done every day". A video talking about what routines you as a real tanker in war actually followed. Historians often dispare because they have the official story an manuals, but when the soldiers pass the unwritten knowledge passes with them. You could rectify that. However, you might need to wait until you retire? ;)
I loved the talk about sleeping on the Bradley when you have dismounts. I’d be hated by my infantry if I was a Bradley commander. I would literally tell my dismounts “bitch please, this is my vehicle, you just ride in it. You are the poor bastard who got the infantry duty, you can pitch your tent out there and sleep in the dirt 🤣”
Not called a stern because it isn't. Like most military ideas, it's very straight forward. Stern comes from stjorn which means "steering" in Norse. It would be confusing if you called it a stern without a stern (stiarne Frisian spelling meaning "rudder"). Like I said, very simple reason why a tank has no stern, because it has tracks.
@@baastex At this point the nomenclature is not going to change anyway, but theres two things wrong with that. First, of course not all tanks or "not" tanks have the power in the back. Second, the steering is done by the tracks, not the power pack. Consider how a rudder steers compared to how a sail or boiler powers.
@@baastex notice how a rudder isn't a propeller. We're not talking engines or propulsion, but the thing that contacts the medium for steering. On a car, that would be the tires, not the engine, on a tank it's the tracks, not the engine, only on a boat can it be the engine if mounted on the stern. There is no configuration where the steering is done from a specific location that can universally be called "steering" and nothing on a tank remotely comes close to a rudder. It's why a tank has a driver not a pilot, there is no rudder to be piloted or a helm for a helmsman. You're not guiding a tank, you're steering it. Or at least your commander hopes to fuck you are not asking the tank if it is willing to maybe go a place at some point in the near future.
1st Steering is done by the transmission sending either more power to 1 track or the other or just removing power on 1 side or even heck send the track into reverse the track only carries the tank and transmit the rotary force of the engine into the ground as liniar force. This is the same as a rudder shifting the force from the propellor to one side or the other as that is how a powered ship steers by guiding the propulsion 2nd Most large ships these days don't even have a rudder anymore as the forces of the ships side would snap the rudder... these use turnable propellers (forgot the name Ships aint my bread and butter) that bypass the need of a rudder as they guide the force already into the correct direction 3rd Seriously saying that the tracks are the thing that steer a tank makes as mutch sense as saying water steers a ship... I understand the name will not change I only said a argument could be made...
@@baastex 1. No, the transmission doesn't do that. The differential does that. And like I said, in this case the word is referring directly to the thing in contact with the medium used for steering on, I.e. air, water, dirt, pavement, so on. 2. Modern ships didn't exist in 1945. 3. I didn't say tracks are exclusively used for steering, but they are what steers a tank. When you move the controls the tracks being in contact with the ground is what's important here. Yes, everything else needs to be there to send the driver's command, but the tracks are doing the job of steering. If a track breaks on a moving tank, the other is going to steer the tank. Forget it, if you haven't got it by now, you don't want to get it. 4. Bonus round. "Rear" and "back" are fine. Those words work wonders. Any sighted soldier can immediately tell where the back of the tank is. Wonderful for training. Yes an engine can be a stern, but a track can never be a rudder.
Yeah those sensors on the Panzerhaubitze are measuring the velocity of the rounds, a way of knowing if the rounds will hit short or far. That measurement is called "v0" in swedish, no idea if its the same in english or not. // Soldier in the Swedish artillery.
I mean you COULD put the engine in the back and the ramp n the front if you wanted to get all your infantry killed Higgins-boat style and to make the ramp super heavy since it would need all the front armor.
I'm not sure why you admit to building scale models like it's an embarrassing thing. What are any of us going to do to you? Call you a nerd until you come knocking on our front doors with 120 mm HE round?
I had a friend in the motor pool - did Humvees over in Iraq. If they had an oil leak, they'd take one of the engine/drivetrain crates from the stack to the ceiling and replace the whole thing. Which was faster than fooling around with changing a valve cover gasket.
