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Army's Mechanised Infantry Vehicle

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Given that wind up is more of a problem with a 6x6 Stolly than a 4x4 vehicle, can anyone explain why the army are considering using a new 8x8 wheeled APC, the Mechanised Infantry Vehicle?

How will wind-up be minimised to an acceptable level?

 

Wind up in a Stalwart or other Alvis FV600 series vehicles, or Ferret and Fox to is attributed to the 'H' drive train layout and one central diff in them where all wheels on one side theoretically have to travel at same speed but almost impossible when on bends or tight turns. Advances in drivetrain layouts today mean this is not so much of a problem.

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Agreed - it's just the lack of differentials that causes wind-up in a Stolly. Provided that a vehicle is properly designed for prolonged road use (the Stolly wasn't) it shouldn't be a problem.

 

Andy

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Dear All,

 

IMHO all the Stolly needed was a means to declutch the fore most and rearmost wheel stations when not needed. Then there would be no wind up loads on the transmission.

 

John

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Dear All,

 

IMHO all the Stolly needed was a means to declutch the fore most and rearmost wheel stations when not needed. Then there would be no wind up loads on the transmission.

 

John

 

There's a rumour that the still-born Mk.3 Stolly (with K60 engine) could do exactly that.

 

Andy

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Dear All,

 

IMHO all the Stolly needed was a means to declutch the fore most and rearmost wheel stations when not needed. Then there would be no wind up loads on the transmission.

 

John

 

Some private owners have done just that.

 

Richard

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The problem of wind up is overstated anyway. None of the vehicle manuals even mention it, and as long as tyre diameters are within specification it largely just results in additional tyre wear.

 

Cheers,

Terry

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The problem of wind up is overstated anyway. None of the vehicle manuals even mention it, and as long as tyre diameters are within specification it largely just results in additional tyre wear.

 

Cheers,

Terry

Terry,

The military publications never state problems or fault finding in these Alvis and Daimler vehicles. Things like that are largely taught on the courses. Having been working on these vehicles over a 40+ year period I can assure you the 'wind-up' is not overstated. Even with all new tyres on, once you turn the steering and drive on a hard surface all the wheels on one side of the vehicle are trying to travel different distances yet being driven together, This means all clearances in the gear train and tracta joints are being taken up, which also means high friction levels and stress, especially in Tracta joints.

 

regards, Richard

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This is when the 3rd diff in the driveline comes into its own. If you take a standard set up with a lockable 3rd diff and do a test most notably on an unmetaled surface, A clear difference can be seen and heard in the drivetrain turning without and with it engaged. I used to run a Terberg 8x8 and one driver could break half shafts on the first corner when he went from the unmade opencast road to the metaled haul road then forgot to disengage it after use. When a multi axle vehicle is turning each axle is following a different arc therefore the wheels need to go at a different revolution to the next in line. Off road tyre slip evens things out but on hard ground that effect is lost so wind in a conventional driveline occurs and axle fight is the result. Leading to higher fuel consumption, high wear patterns and broken parts. With an individual drive on each wheel station either electric or hydraulic the problem does not occur but a different set of problems manifest themselves usually to do with heat.

Edited by john1950

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I recall playing around at Shrivenham (whilst doing my engineering degree) with a Ferret fitted with viscous couplings rather than universal joints and as such did not suffer any sort of wind up.

 

 

Unofficial SOP for stollys back in the day was to make one side bounce up a kerb or two to relieve wind up.

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Wind-up; an interesting subject but one that I can also say that I never heard of in the Army, when driving Land Rovers! I only knew about wind-up after leaving ad later buying an MV. All I was told in the Army was don't drive on the road in four wheel drive, which at the time seemed logical as once back on the road we wanted to drive at the road speed limit not crawl along.

 

Richard's point about wind-up on the road as soon as the steering wheel is turned, made me wonder whether it would be OK to drive my Lwt in 4x4 in a straight line as in May each year I take part in a parade of MVs and other vehicles that moves so slowly, that clutch pumping is getting to be a bind on my knee. So far I have resisted using 4x4 mode but if it is a very straight 1 mile parade, then I trust it would be ok to be in 4x4 second gear and trickle along?

Edited by LarryH57

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Richard's point about wind-up on the road as soon as the steering wheel is turned, made me wonder whether it would be OK to drive my Lwt in 4x4 in a straight line as in May each year I take part in a parade of MVs and other vehicles that moves so slowly, that clutch pumping is getting to be a bind on my knee. So far I have resisted using 4x4 mode but if it is a very straight 1 mile parade, then I trust it would be ok to be in 4x4 second gear and trickle along?

 

Larry,

The remark I made about steering related to those vehicles with H layout of driveline and one central diff only, ie Saracen, Stalwart, Ferret, etc. The wind up referred to is between each wheel on one side.

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A L/R Freelander is in permanent 4 wheel drive, fitted with a Viscous coupling in the rear driveshaft.

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Larry,

 

No problem at all, even on curves. Sharp bends will kick back on the steering a bit but not an issue. I often do this trick in traffic with my Series 1, low range first or second and tickle the hand throttle. Just remember to take it out of low when the traffic clears!

 

Gordon

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Thanks folks; perhaps all the warnings over driving in four wheel drive on the road during the parade was a 'wind-up':-D

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On something like a Landrover in 4x4 it is down to how long and how many curves you drive round whilst in 4x4. My Unipower is permanent four wheel drive with no centre diff. On the road no issues as left and right corners seem to cancel out any wind up. The times I do notice it are tight manoeuvring on hard surfaces. On those occasions she will skip a wheel when the wind up gets too much. Disconcerting the first time she did it but used to it now. On grass or any form of loose surface no issue. It would be nice to have a centre diff to remove the stress and friction but it's the way it was built and everything is massively overbuilt on it.

 

Ed

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A lot of older 3-axle military transport trucks see some results of a wind-up as well, the original M35 (deuce-and-a-half) with the sprag clutch for the front axles had the potential for all 6 wheels to move at different rates and even just having both back axles driven at different rates.

Many collectors fit hubs so they can unlock the front and sometimes back axles and report much improved steering, tire life, and fuel economy. In cases where locking hubs are not available, or they would alter the look of the vehicle in an undesirable manner, it is common to find some extras and de-spline hubs you don't want driven and just swap back in the originals should you think you might need the traction.

Of course, the modified driveshafts for the Stolly have the same utility.

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It was common to see Stalwart's and ferrets bouncing off curbs when following them. I wandered what they were doing when I first saw it but then someone explained they they were bouncing/jumping off the curbs to allow and wind-up to be let out.

There are no plans to introduce wheeled Inf Armd platforms at the moment. We are waiting for the Scout family of vehicles to come into service, but I can honestly say I am not aware of any plans for a wheeled 6 or 8 wheeler yet.

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It was common to see Stalwart's and ferrets bouncing off curbs when following them. I wandered what they were doing when I first saw it but then someone explained they they were bouncing/jumping off the curbs to allow and wind-up to be let out.

There are no plans to introduce wheeled Inf Armd platforms at the moment. We are waiting for the Scout family of vehicles to come into service, but I can honestly say I am not aware of any plans for a wheeled 6 or 8 wheeler yet.

 

Maybe He is thinking about this from BAE for the US marines:

 

http://foxtrotalpha.jalopnik.com/one-of-these-will-be-the-next-u-s-marines-amphibious-1746202361

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