[MV] Re: Ferrets - PS

Jim Webster (jimweb@patching.thegap.com)
Tue, 18 Nov 1997 20:59:56 +0000

Alan Bowes wrote:

> I'd agree with Jim's comment that neither model of Ferret would be a
> good high-speed vehicle, and that the MK 1 might be a little less
> likely to roll.
>
> Jim, see if you agree with my thoughts on this topic. Since you have a
> lot of "real world" experience driving these vehicles, your input would
> be valuable. Anyway, here's my theory, right or wrong:
>
> The CG on the Ferrets doesn't seem to be terribly high relatively
> speaking. However, they have a fairly short wheelbase relative to
> vehicle dimensions, plus, I suspect that they were designed with less
> understeer to improve maneuverability. This would be an unstable
> situation for high-speed cornering.

Because of the numbers of amateur ferret drivers out there I am switching
this message to the mailing list as it could be important,, now where was
I?I agree it isn't terribly high. The 'fly in the ointment' so to speak is
the wheelbase and I suspect the wheel size... incidentally they cured all
these problems with the big wheel ferrets - unfortunately the army brought
very few of them. I still wonder how making the wheels larger cured the
problem...

> Even if they are designed with some understeer, they still couldn't
> take advantage of as much understeer geometry as is possible with
> longer-wheelbase vehicles. Understeer provides less-responsive
> handling, but more stability. In an understeer situation, the rear
> wheels describe a smaller arc on turning than the front wheels. This
> means that on a vehicle with less understeer and a larger rear wheel
> arc relative to the front, the center of inertia vector is more
> laterally aimed in a turn, rather than diagonally over the outside
> front wheel. In other words, when cornering, the inertia of the vehicle
> with less understeer tends to want to roll the vehicle to its side (the
> shorter dimension), while the inertia of a vehicle with more understeer
> will try to roll the vehicle diagonally (the longer dimension), which
> is more stable. The greater the difference between the front and rear
> turning arcs (front larger), the less of a tendency there is to roll in
> cornering, but the less maneuverable and responsive the vehicle.

> If the center of gravity is high and combined with very little
> understeer or some oversteer, this will make the situation even worse.
> Vehicles with neutral understeer (or even some slight oversteer) are
> generally very low-slung "sports" vehicles, in which case the low
> center of gravity or roll center will have much less tendency to want
> to roll the vehicle and they can take advantage of the more responsive
> handling that neutral understeer or slight oversteer provides.

> Another situation that can cause cornering problems relates to
> inconsistent steering characteristics, such as when a vehicle enters a
> turn in an understeer situation, but with body lean, it changes
> suddenly to an oversteer situation, which can require immediate driver
> correction to overcome it...if it can be overcome. I don't know if that
> applies to the Ferret or not, since I haven't driven one, but maybe Jim
> could provide some input on that.

That about sums it up [ I think] and to 'idiotize' it - Don't make sudden
steering movements particulary once you are committed to making a turn. In
addition we used to try make the CofG as low as possible by packing all
the heavy kit in the bottom of the bins/vehicle. It worked to a certain
extent but in the end it boils down the experience of the driver. A driver
with enough experience can overcome the deficiencies of any vehicle
providing he lives long enough.

> Some problems you'd have in the back country would relate to weight,
> such as collapsing soft roadbeds, light bridges, etc., the difficulty
> of emergency maintenance, and the difficulty of another vehicle
> extracting the Ferret if it gets hopelessly stuck. In addition, its
> relatively poor visibility (maybe not so bad over the front), lack of
> cargo capacity, width on narrow roads, and interior heat (formidable in
> the Arizona summers) would be some things you'd have to deal with.

Weight isn't so much a problem I think.. we used to take the vehicles
everywhere and they rarely got bogged. When they did we usually extracted
them with one of those hand-crank-winches - never use another ferret.. that
is unless you liked being sprayed with red hot oil from the fluid flywheel.
Incidentally the flywheels are the worst part of the ferret.. wait till you
have to replace it and you'll find out. Usually they don't go that often
thankfully.

> That said, I still think a Ferret would be a blast. It may not be a
> practical back country work vehicle, but it would be great fun to
> drive...slowly. I'd love to have one.

They are very nice to cruise around in.. but again only when you have the
experience AND despite the fact that some of them can clock 70 or more -
don't bother unless your very experienced and have enough insurance to keep
your dependents going after they scraped your brains of the road..It was
always a major concern when we had to get new drivers so whenever we had to
have a driving course we always borrowed a Mark I - it was safer and then
weaned the drivers onto mark II. Having said that I survived 4 roll-overs
while commanding one and each time I saw it coming - an inexperienced
person may not. BTW the thing that usually kills the driver are all those
mounting bolts inside the hull - WEAR A HELMET! The poor old commander
usually gets thrown out by the centrifugal force of the spin so if
something unusual seem to be happening don't try to climb out -head for the
floor of the vehicle and hold on tight. NEVER let your commander ride sat
on the turret.
You wouldnt believe where the CofG is when they do that.

> 12,000 dollars seems to be a typical ballpark figure for 1970's Ferrets
> in complete and running condition. I believe that the vehicles in the
> following sites were priced in that range.

Some Ferrets seem to get reputations for rolling and certainly seem to have
a propensity for it. If your going to buy one watch out for ones that seem
to have more than their fair share of gouges, particularely around the
corners of the armour. Whenever a repalcement vehicle used to come in it
was very difficult to get the crew to take it if it was 'blighted' ie gouge
marks and a new paint job inside. It was quite amazing how often such a
vehicle would suffer a major problem and have to be replaced.

Just to hark back to the Mark 2/3 - thats the one with the even higher
turret and the fiuttings for Vigilant.. after the Vigilant went out of
service we sometimes got the odd one stripped out for use in the recce
role.. the first thing we did was collect all the scrap tools we had and
put them in the side bins and then pour in sufficient concrete to cover
them... So if you come across one you'll know it served at some time with
the 9/12 Royal Lancers {Prince of Wales's Own]

Speaking of which I think I have enough ferret stories for an article for
the mag...

TTFN
Jim

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