*This message was transferred with a trial version of CommuniGate(tm) Pro*
-----Original Message-----
From: Ian Wallace <iwallace@uswest.net>
To: Military Vehicles List <mil-veh@uller.skylee.com>
Date: 01 April 2000 23:11
Subject: [MV] How Hot is Hot
>
>Ferret & Saracen Owners
>
And Saladin, Stalwart and Salamander too.
> - how hot do your bevel boxes and hubs get after a
>brisk drive? Warm? Hot? Too hot to hold your hand on them?
>
Yes, yes and yes.
You won't find many people with arms long enough to reach FV600 series bevel
boxes but the 5 pinion epicyclic reduction hubs in these do get hot. It seems
to be possibly dependant on the number and nature of curves in the road with
tyre radius matching causing variations in wind-up and loading from vehicle to
vehicle.
The Ferret has a relatively low vehicle weight and reduced scrub resistance
compared to the FV600s having one wheel less per side and 9.00 x 16s compared to
11.00 x 20 and 14.00 x 20s on the FV622/3/4 but proportionally larger hub
drives.
I do know my 623 gets hotter than a known Seattle based 622, also we have more
sharp curves and my tyres are not 6 new matched ones. In winter they stay dry
on wet days and are pleasantly hot, summer has them on the point of stinging
hot, quite unscientific but a few seconds before painful hot is only about 45ºC
if that.
Perhaps to a lesser extent on Ferrets but very noticeable on the 600s is that
they are even more stunningly gutless than normal until the copious quantities
of gear oil has warmed through, I have several times almost pulled over in the
first few miles to investigate a noticeable loss of power but before a suitable
pull in presents itself all seems to be back to normal, you learn to live with
this.
By way of comparison a suspended FV623 with all six wheels turning air needs
about 1/4 throttle or so to show an indicated 20mph in top, thats just 60HP
churning the 15 imp gallons of 90EP contained (temporarily at least) in the 13
operative gearboxes necessary for wheel driving, leaving out the actual gearbox
itself having SAE 30 in it.
>I have just
>checked the level of all fluids in the drive train and now I am curious how
>toasty these gear boxes get. I certainly don't want to fry a seal, but on
>the other hand if it's sort of like a car or truck, the drive train gets
>pretty hot after freeway speeds (50 mph for 5 miles or so), and that's
>normal. I'm using the recommended weight gear lube, all up to the level of
>the "check" plugs.
>
That doesn't seem too unusual, lipped oil seals (using the term "seal" loosely,
as they do) are used in the engine running continually at around 100ºC and the
transmission at this temperature would be very noticeable. The hub drain/filler
plugs should be at 90º to the vertical when checking of course.
Lets not forget that we often operate these vehicles well outside their designed
role, mile upon mile of high speed freeway thrashing was not in Mr. Daimler's
mind when he put pen to paper for the FV701 I think, but it likely was when he
did the Daimler Double-Six (XJ12).
Richard
(Southampton - England)
This archive was generated by hypermail 2b29 : Mon May 01 2000 - 05:30:04 PDT