Inside the Chieftain's Hatch: XM808 "Twister"

the story of xm808 starts 1963 in sunnyvale california now the army had previously played around with the 8x8 vehicles for example the t-55 gun motor character it's an 8x8 tank destroyer bogey at the front of four wheels spoke at the back of four wheels and that was based off of the cook interceptor but lockheed missile and space company thought that they could do better not only with independent bogies but by a fully articulating vehicle the result came out in 1965 was a vehicle known as twister now this was simply a proof-of-concept mobility test bed vehicle but it did prove to be able to go anywhere the tracked vehicles could go as well as go there faster well eventually this caught the attention of the army and taekon put out a contract for four improved twister-type vehicles one was going to be just an unarmored mobility test bed one was going to be an open-topped armored vehicle won a closed topped armored vehicle and one a swimming test vehicle however budget cuts hit and they had to cancel the open-topped armored vehicle program but one of each of the three continued on to be built july 1969 the first vehicle comes off the assembly line and that was a swimmer test vehicle the armored vehicle came out in september and then november was the arrival of the mobility test bed so capable with these vehicles the lockheed martin had to construct a special test course to try to run these things through their paces before they were delivered to the army so they could find out a couple of snags that were fixed beforehand early 1970 the xm808 arrives in aberdeen proving grounds for safety tests once it passed the safety test it was then shipped off to fort knox for actual testing as mentioned only the one xm808 was built in the armored form and it is now here at the fort benning u.s army armor and cavalry collection and it's looking a little bit ready because it's spent 50 years outdoors the first time it has ever come indoors was about 15 minutes ago uh i they were still putting this in place as i'm setting up the camera equipment so now it is finally in a protected condition and considering it spent so long outdoors is actually not in bad condition either so anyway without further ado let's go around and see what makes this guy special the vehicle is described as an articulated 8x8 vehicle of two aluminium hulls connected by a pivot yoke structure each hull has its own drivetrain which basically means it's a two four by fours bolted together now as we're going around bear in mind that this was a concept vehicle that was not designed for a service requirement like most other vehicles that i cover this means that they made various decisions based more on the basis of economy than on the basis of whether or not it would truly fit a combat requirement no combat requirement was set up for this vehicle they're just testing it out to see what works and if the concept is worth further development so starting off with the front hull as mentioned the entire vehicle is aluminium so it's a welded aluminium structure inside and on the armored version they have basically applique steel armor plate on the front so it's both bolted on and there is adhesive as well so the adhesive performs a couple of functions it helps reduce a little bit of the spalling there's a certain set thickness of the adhesive it even helps with some of the sound deadening but the notes do indicate that the bolts could be a problem in combat should the vehicle be hit so obviously for a combat vehicle instead of messing around with the welded interior which was common to most other vehicles so the other 808s were pretty much similar from the whole level except without the applique steel a real combat vehicle would be made of welded steel to begin with so that's your first difference inside the engine the powertrain is a little bit offset so the engine is located back here the radiator and transmission are on the right hand side the shaft i'll just put up a diagram the shaft comes forward to a transfer case comes over to the first differential from the differential it goes to two outboard stations for the wheels and the third shaft comes back to the second differential for the second axle now these differentials are not limited slip they're regular differentials which is a problem but again we have another case of the vehicle being designed for a concept road when they first built this it had limited slip differentials on the front hull as well the problem was that during that testing at lockheed's facility before they shipped it to aberdeen they realized that there was just so much pulse power the the torque was going in waves that the differentials kept snapping so there were two solutions one was to install a thicker more expensive limited slip differential or the other one was solid we'll just take some regular diffs put those in and we'll bear in mind if we ever build a combat vehicle we'll put the limited slip diffs up front by and large it didn't prove to be a problem in the testing process there were some points where the vehicle would bog down and it would slip and the differential was not getting the traction if that made a lot of difference nobody knows but of course that's what physically happened in the testing and that's what is in the report it got so far and the wheels started spinning couldn't be helped they had a budget to meet for a concept vehicle so now we move around to the wheels on the side okay i'm going to start with the elephant in the room which is that these wheels are not the same remember i said this vehicle was put in here all of 15 20 minutes ago and because these original wheels are so old and battered what they had to do is it took some wheels for the v150 it turns out the lug pattern is the same and you put those front and rear for the sake of moving it into position they've jacked it up eventually they're going to get around they still have them they're going to pull off the v150 wheels and put back the original wheels which are back here now these are 18-24-ply 45-inch diameter with self-cleaning treads and you'll see immediately it is much wider than a v-150 wheel something else that is a little bit unique about this tire is that the tire pressure is all of four psi at the front now and remember generally speaking on a wheeled vehicle ground pressure equals the tire pressure now there's a quirk with this so for example the side walls here add a little bit extra strength so the actual ground pressure and testing for this four psi tire was five psi and yeah they don't make them anymore apparently so that's why they had to use the v150 and sadly they are in a bit of ragged shape but it's on jack so it'll look fine for the rest of this vehicle's career as a monument to science only the front wheels were steered these wheels are fixed in line with the hull and so when the vehicle steers you're going to get a synchronization between the front wheels on acumen steering and then the actual articulation of the front hull by use of a hydraulic ram the wheels were rated to go up to 50 miles when flat now i'm not sure there's much of a difference between four psi and flat but there you go on the front hall where we have our low visibility lights convoy marker lights infrared and service drive headlights pretty common design of the time you'll see those anything up to you know m48 tanks m60 tanks actually by this point and then you get to the pivot yoke structure so this is your pivot point for the pivot yoke system if you consider this to be like the forks on a bicycle you won't be far off the weight of the vehicle is split about 60 40 and the 40 is at the front hole so it comes across this cross beam here to each side of the front hull the weight is then taken by the shaft which angles slightly forward and hooks into a pivot point more or less in the middle of the front hull it's not a full axle it's just a hinge on each side and this is your pivot point purely for pitch so the front bogey will raise in pitch up to 35 degrees and it will go down in pitch 27. now you will have noticed that the most furthest forward thing on the vehicle is actually the wheel which technically means this has an angle of approach of 90 degrees in actuality it could only cross maybe a three foot wall but it does mean also that if you're going down a cliff or a near cliff you can still make it because the wheels are the first thing that will hit all right so this is where is the roll and the yaw and bear in mind the entire weight of this vehicle 40 of the 10 tons is coming through this one joint here roll is up to 30 degrees you can see a little rubber bump stop down here and that is your pivoting left and right and then for you for steering the vehicle there is a single hydraulic ram on the left hand side and again you can see a little rubber bump stop here for when it gets too far to the left now steering as mentioned is a combination of the front wheels and the hydraulics so the front wheels the inside wheel when turning would be up to 19 degrees of deflection then you add the articulation of the vehicle itself originally that was 35 degrees however there were there was a breakage and a field repair kit a little bit stronger was sent out but it again they did sort of on the cheap so it actually limited the articulation to only about 21 and a half degrees from that point on presumably that is the modification currently in place on the vehicle i can't imagine why they would have spent the money to change it back again the manual is not specific or at least the test report is not specific as to what happens when you turn the steering wheel and the vehicle is stationary however there is a note that the low steering low speed steering response was sufficiently poor that they had to upgrade the hydraulics from 9 psi to 13 psi to make it more controllable so the implication is there is an actual curvature and dragging of the wheels if you're completely stationary and attempt to turn the wheel so we continue walking back i count six layers of laminate inside the glass here and you go to million pretty good vision radio antenna horn we are fairly sure this is the fuel filler port but we can't open it uh fire extinguisher handle and then you go a little bit further back by the way the only driver's door per se is the hatch up on the top indicators oh the rear tires they are six psi with a ground pressure of eight when you come around the back regular tail light stowage bin cooling air intake rear windows and then a simple swing open rear door see a couple of tow hooks electrical connector down here so it's is in surprisingly good condition considering how long it has been in storage outdoor storage well obviously the hinges need a bit of work now the powertrains front and rear are going to get to in a second are not identical but a lot of the major components are both engines and both transmissions are the same the engines are chrysler h440s that's a 291 horsepower v8 440 cubic inches also puts out about 400 foot pounds of torque power comes back into a transfer case four gears to transfer the power sideways again front and rear have the same then it goes forward into the same allison transmission it is a six-speed transmission and then from the transmission it goes forward again to another transfer case where it goes towards the center of the vehicle now both transmissions actually change on their own but for whatever way the vehicle was designed it turned out that they changed within a fraction of a second of each other anyway so it was never any problem other things you seen it looks like we have an oil header tank we got the radiator now this one is mounted at 45 degrees because you have a bit more room in the hull but the front radiator is mounted fully flat but could rotate up if you lifted up the engine deck the engine deck by the way is completely bolted in and that's why i haven't opened it but i don't need to because it's basically the same then things start getting different i already mentioned how the front hole the transm the after it goes from the transfer case back to the middle comes back into a into a differential and then gets split three ways two wheels and then the rear axle this one is a little bit more complicated i'm going to get to that one to get around the side so when we left the powertrain and gone forward from the transmission to a transfer case to go towards the center in the center it will then go forward not rearward like in the front hole to the differential this differential is a limited slip differential it turned out that whatever the stresses were they weren't so bad on the main hole from there you go outwards the two drive shafts each drive shaft has a disc brake now there are six disc brakes on the vehicle one for each drive shaft on the rear hole and one for each individual wheel on the front hull then once you go past the disc brakes you then go into the trailing arm so you can just see the training arms come down at an angle and this transfers the power down to the main suspension units now to do this there are three cogs it's a hollow training arm it comes down to the level of the pivot point there's a shaft which comes from the trailing arm to the walking beam so this is a walking beam suspension from here there are then four cogs forward and four cogs rearward actually no wrong three cogs forward and three cogs rearward to transfer the the power within the walking beam again it's a hollow walking beam to the axles when it gets to the axles there's a final reduction somewhere and then you get the power to the wheels you might think all this causes a little bit of resistance it does you'd use 60 horsepower on the rear engine just to overcome the resistance of the powertrain and the accessories you lose 40 horsepower on the front hull because it's not quite as insane so that's a catch the other catch is as a result fuel economy on this thing was abysmal you were doing well to get two miles to the gala and that was on the roads combined fuel economy was 1.7 miles per gallon that's at 40 percent cross-country for comparison the m113 2.6 miles to the gallon so this is pretty abysmal the fuel tank is 84 gallons well we saw the entry point earlier and it's in the crew compartment which also of course means that you need to have piping going forward to the front hull for the fuel other controls you have the accelerator cable goes to the front hole and presumably something for the transmission although i have to say i didn't actually see it in the manual so as you come up then to the top hole stow spin at the back the exhaust pipe is deflected upwards this appears to be another stowage bin unfortunately it's spot welded the things in place the one on the far side i note has piping a little and a little exhaust pipe which i think indicates a personnel heater but i haven't seen it in the manual again windows fantastic you can see out and then this brings us past another indicator to the observer scouts door that's what it's officially called so you crank down it stuck in place but it does swing open and i can climb in and my immediate thought is that if you want to get out this way or in you've got to make sure that the last thing you did on your steering is to turn left because that way you can open this up a lot more the hole right now is pretty much straight so you can imagine if the hull was traversed to the right this wheel will come back and he wouldn't be able to open the door at all fortunately there's a hatch up top as well not easy ah builders plate well i mean there's a few things in the way that i hope wouldn't be there in the real vehicle either way they're just catching on my jeans there were two drivers positions there's head down and if you want to you can open the hatch and go head out although in fairness this is extremely drivable because there are two positions head up ahead out the brake has two pedals there's the the standard standard brake pedal here and then there's one higher up just to the left of it they can use if you're higher up although i note that the accelerator pedal does not appear to be uh that way i guess unless you have this tiny little thing up here but i do note the little ledge that as you're bouncing around cross country it'll keep your foot in place you're just a little bit angled to the right it is a little bit tight for those who are wondering i learned to drive in a ford fiesta and i did a lot of driving in ford fiesta like this cross-country if you're wondering why i'm a lot i'm reasonably tolerant of small spaces but by american standards this is a small space steering wheel to the front nice and simple i note there is a disconnect here for the ackermann steering if you're going to tow the vehicle flip this valve saves the steering hopefully they did that if not while this vehicle was never going to drive again anyway i don't think interestingly when the vehicle was delivered these cracks in the windshield were already there and it was mentioned in the report nobody knows how it happened to why it happened but it's there as you look at the dash it's simple enough so you got temperature gauges front and rear you got a single speedometer two rpm gauges your speedometer of course the vehicle would max out at 65 miles an hour which isn't bad for a vehicle that came in at twenty thousand eight hundred pounds as i recall actually it's got it since it has a data place here gross vehicle weight twenty thousand six hundred eighty two pounds which i presume is including the crew uh shipping damage nine point six two tons ah shipping weight so i guess empty ish nineteen thousand two thirty six um sorry you can read it for yourself i'll just put it up you see two transmission levers because hey we've got two transmissions now there's no indication as to why you couldn't do both transmissions off of one cable but there you go coming down we got the fuel tank lever generator presumably on the back choice between blackouts those are the small ones at the front and the infrared service drives uh let's say start rear engine first okay good to know i don't know why a standard headlight switch everybody's familiar with it there's a high beam selector there's a dimmer selector here initially the accelerator pedal was a physical cable that ran forward and rear but they they eventually realized it wasn't working well and they needed to convert it to a hydraulic system there's not really much else to be said i mean you can you see reasonably well out of the vehicle yeah i see well that's interesting what that is yeah i see the fuel filter fuel fill comes down and back behind me the 0-60 time was 25.9 and it would do the quarter mile for those who are interested in 23.4 crossing the line at 56 miles an hour which i'm sure there's a lot of volunteers you know we got to test that again and again just to make sure braking was 60 to zero in 300 feet or less actually 298 but the brakes weren't particularly strong so after a couple of goes at that the brakes exploded so there was a note in the test report saying you know we need stronger brakes if this ever android service when it came to the actual driving experience the report notes that well firstly you have to train people very carefully and very slowly because of the quote unique characteristics of the vehicle but once you figured it out apparently the drivers really liked it so steering was very precise it was very low effort at least once they increase the pressure on the hydraulic ram very easy to steer it had a tendency of under steering when you went into a turn not least because your mostly weight is on the rear hull which is always pointing straight forward and you only had the two wheel steering and a little bit of yaw from the hydraulics once he got turning then the vehicle had a tendency to oversteer which if you've ever done that it's a lot of fun so i can only imagine people careening across country over steering uh this uh vehicle they really like the only problem the only complaint that they had was it was ungodly loud and he needed to wear hearing protection and eventually they installed an intercom system the test report says it needs one i guess they put one in because i see the the j boxes scattered around to his right i'm not going to sit in it because just a chair the observer scout and there was originally it was some contemplation given to making him fully parallel with the driver but they didn't see a point it seemed just the excess of space and by putting him a bit further back it was a lot easier for him to dismount the vehicle so next stop the commander's position okay so you come into the tc's compartment i strongly suspect you just get in through the hatch i do think that you can fold forward the observer scout seat but it's frozen in place if it is possible to do so either way getting in hats is probably a lot simpler it's considering getting thrown around there's a lot of things that you can hurt yourself on i think that is my single biggest worry it's not that you're uncomfortable it's that this is a fast off-road vehicle and there is a lot of things in here that you can break your nose on on the right hand side i see a radio rack a bit of stowage you see the spare the external power port for jump starting or slave starting whatever you call them these days um so the seat has a backrest amazingly enough the cupola again this is just saving money let's get what we have the koopa is the m27 that comes right off of the m114a1 so it came with the 820 it's uh the m139 in american service hispanic swizza and it was never well regarded by the us to aim it it is a fully hydraulic turret so you have a set of cadillacs here that you can spin left right and elevate up and down the catch is that the sight is outside it's fixed next to it's actually attached you bolt it on next to the gun and it's either a daylight sight a by seven or the night sight is the nv2a and if it gets dark you just bolt the other one on so you're kind of sticking ahead out aiming through the physical sight like a rifle a huge rifle optic and you're controlling with the hydraulics down here ammunition capacity on the right hand side as i recall is 75 rounds of 20 millimeter now it's not a dual feed system the the ammunition belts were alternating between ap and he so you'd fire both and hopefully the ballistics were the same the ap round was rated for about 47 millimeters at 100 meters or so to 30 degrees or 28 millimeters at 800. now there are quite a few selections here for the fire type so you can fire single shot five round burst or full auto and the rate of fire was selectable the slow rate of fire slow was 200 rounds a minute and the high rate of fire was full cyclic and that was between 850 and 1000 and something rounds per minute it's pretty insane especially considering you only have those 75 rounds ready to go mounted outside a total of about 400 rounds will be stowed around the vehicle that's basically anything i can say about this uh this commander's position so i cannot get out the hatch so yeah that's not happening oh wasp nest again this vehicle is outside we're going to tell him um yeah so i guess i'll just get out and close up the old-fashioned way so what was the end result of this experiment well firstly it was faster and with a better ride than anything else the army put up against it it would even go places the gamma go couldn't go on the other hand there were places that the m113 wouldn't get stuck but this did particularly in particularly loose soil or mud hills but there's no way of knowing really whether that was the fault of the fact that they didn't have limited slip differentials therefore just an inherent design issue fuel economy as mentioned was pretty horrible there was some consideration given to putting diesels instead of the petrol engines but that would have added over a quarter ton to the weight and it was wonder whether or not that would affect the mobility the liability was absolutely awful so you had an average mean time between failures of five and a half hours of operation by way of comparison an m60 tank was running in about 11 and a half and a gamma goat at 35 when it was down it took a long time to repair not least because most of the things that broke tended to be under the engines so you had to pull the engines out to get whatever it was that needed fixing for every hour of running time you had two and two thirds man hours of maintenance by a comparison you expected to get point nine of an hour for an m60 and about half an hour at worst for a wheeled vehicle and somewhere less than point one of an hour of maintenance for every hour of running time in the end though of course this is only a proof-of-concept vehicle all they wanted to see was whether or not they could get a vehicle that could run quickly and well off-road and in that they succeeded there was of course no future for this vehicle and no others were ever built lockheed did revisit the concept with the xm800 wheeled the also known as the 806 it was the entrance for the armored scout reconnaissance vehicle program it did not do anywhere near as well so that's it i hope you found the tour interesting and informative thanks to the us army's armor and calvary collection for letting me roam around and also to the patrons who have funded this trip out here for me to film it for you so that said take care and i'll talk to you on the next one ah so does i do that intercom box behind me heater control dome light what's this it's red and white air cleaners one for each so it's a restriction gauge for the air cleaners come 1963 though something happened let's warm my way in here getting into this thing is a little bit more difficult because i have the tripod right in the middle of where my legs would ordinarily go so this is not representative i also have a very large audio recorder what the hell you can't get in does the seat fold forward no oh hang on what's this and there's a hinge i think the seat folds forward unfortunately i can't get the damn thing to open okay nothing for it i need to turn off the camera and move it out of the way [Music] i wonder if the hatch works probably not with my look they probably welded the bloody thing

Channel: The_Chieftain

Views: 219,489

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Id: opKSpWjueG4

Length: 31min 25sec (1885 seconds)

Published: Sat Sep 11 2021