Hello,

I'm new to this mailing list and didn't realise this type of Q/A mail out
was included.

My comment as an observation from a trailer builders point of view are as
follows:

If the prime movers (if that's what is being used here) have tandem drive
then I would be cautious of using air suspension drive axles. The stories
from log haulers in West Australia are that air suspensions are causing more
damage to tracks than conventional 6 rod, single point drive suspensions.

I found that hard to believe at first but I think it has to do with the air
spring not having the capacity to equalise axle loading as fast as the
suspension is trying to respond to very rough ground conditions. You end up
with higher momentary axle loads on the axle sitting on the crest of a bump
and lower axle load on the axle in the trough because of the momentary
higher air bag pressure one the axle sitting on the crest.

The six rod suspension, on the other hand, will adjust much quicker and
therefore have a better chance of keeping reasonable axle weight
distribution for trackion purposes.

It's not a question of ride quality but purely weight distribution and when
you need good weight distribution to maintain traction over large
undulations the suspension response time is everything.

I also agree with the reduced tyre pressure idea on the drive.

Hope this is useful.

Regards / Dante Travaglini

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----- Original Message -----
From: Automatic digest processor <[log in to unmask]>
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<[log in to unmask]>
Sent: Thursday, December 14, 2000 10:02 AM
Subject: ROAD-TRANSPORT-TECHNOLOGY Digest - 29 Nov 2000 to 13 Dec 2000
(#2000-3)


> There are 2 messages totalling 131 lines in this issue.
>
> Topics of the day:
>
>   1. Enhancing commercial vehicle traction on sandy roads (2)
>
> ----------------------------------------------------------------------
>
> Date:    Wed, 13 Dec 2000 14:55:14 -0600
> From:    "Bradley, Allan HI0" <[log in to unmask]>
> Subject: Enhancing commercial vehicle traction on sandy roads
>
> Hello colleagues,
>
> I am writing to see whether someone can suggest some solutions to a
> transportation challenge that we have here in Saskatchewan, Canada.  Our
> Highways Department recently opened a winter road of about 150 km length
to
> improve access to the far north of the province.  The locals have decided
> that they want to try using the road during the summer at slow speed (<50
> km/h).  However, commercial trucks with standard tires and wheels are
having
> difficulty negotiating the rocky outcrops and pockets of sand (typical
> Canadian Shield landform).  Can anyone suggest any technologies that might
> be tried to increase the mobility of the commercial trucks on this run?
>
> My thoughts so far are:
> reduced tire pressures (Tire Pressure Control System-controlled)
> Super single tires
> Sand/All Terrain traction tires like the Michelin XS or XL 18R22.5 or
> Goodyear 445/65R22.5 G178
>
> Thanks for your assistance with this.
>
> Al.\\
>
> ------------------------------
>
> Date:    Thu, 14 Dec 2000 09:59:13 +1100
> From:    Bob Murphy <[log in to unmask]>
> Subject: Re: Enhancing commercial vehicle traction on sandy roads
>
> Allan,
>
> I heard there were already provisions for tyre pressure variations in some
> Canadian Provinces and had also heard that centralised tyre pressure
systems
> were already in fairly wide use in Canada. Such systems can vary tyre
> pressure while the vehicle is moving and also provide constant feedback on
> system pressure to the driver.
>
> Also a guy named John Woodruffe who most of this group knows has done some
> papers on the effects of tyre pressures on dirt roads (low pressure is
much
> kinder to the road). He is on [log in to unmask] and his snail mail address
is
> PO Box 189, Carleton Place, Ontario K7C 3P4 (though I haven't communicated
> with him in quite awhile).
>
> Also, Freightliner recently announced the availability or planned
> availability of a very wide Michelin single designed to replace duals on
> drive axles. I played around with one of the Engineering Department's
> Century Class test trucks with a set of them on the drives several years
ago
> in Portland. There seemed to be no contraindications but you had better
> check whether they are suitable for use at lower pressures on dirt roads.
>
> I really think at least part of the answer is centralised tyre pressure
> systems and duals in the short term just because with standard tyres there
> are so many rubber compounds and treads available for the arduous
conditions
> you describe that you have the best chance of dialling in the best horse
for
> each course.
>
> I'd be cautious about encouraging the use of the "super" singles or wide
> singles like the Europeans use on their trailers, despite the significant
> fuel advantages and the fact that you can spread the spring centres and
thus
> increase stability. They are harder on pavements than duals. That might
not
> make a big difference in Europe or even in most of the US, given the
> thickness of their pavements etc but in Australia where we have thin
> pavements and in Canada where the base turns to pus when it thaws in the
> spring I wouldn't be encouraging the things.
>
> A couple of centralised tyre pressure systems are now being marketed by
big
> road transport industry suppliers. Eaton might be one of them. They are
> becoming fairly common in Australia in logging applications and have
greatly
> reduced damage to forest tracks here, especially in the wet.
>
> Remember this spiel is from the point of view of a trucking writer not a
> scientist or engineer. I am reasonably certain of the veracity of the
above
> statements but it would take me some time to properly verify the bases.
>
> Cheers,
>
> Bob Murphy MCIT
> IS Edit Transport & Technical Communications
> PO Box 111
> Campbells Creek VIC 3451
> AUSTRALIA
>
> Tel: + 61 3 5476 4408
>        + 61 3 5476 4474
>
> [log in to unmask]
> [log in to unmask]
>
>
>
> ----- Original Message -----
> From: "Bradley, Allan HI0" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, December 14, 2000 7:55 AM
> Subject: Enhancing commercial vehicle traction on sandy roads
>
>
> > Hello colleagues,
> >
> > I am writing to see whether someone can suggest some solutions to a
> > transportation challenge that we have here in Saskatchewan, Canada.  Our
> > Highways Department recently opened a winter road of about 150 km length
> to
> > improve access to the far north of the province.  The locals have
decided
> > that they want to try using the road during the summer at slow speed
(<50
> > km/h).  However, commercial trucks with standard tires and wheels are
> having
> > difficulty negotiating the rocky outcrops and pockets of sand (typical
> > Canadian Shield landform).  Can anyone suggest any technologies that
might
> > be tried to increase the mobility of the commercial trucks on this run?
> >
> > My thoughts so far are:
> > reduced tire pressures (Tire Pressure Control System-controlled)
> > Super single tires
> > Sand/All Terrain traction tires like the Michelin XS or XL 18R22.5 or
> > Goodyear 445/65R22.5 G178
> >
> > Thanks for your assistance with this.
> >
> > Al.\\
>
> ------------------------------
>
> End of ROAD-TRANSPORT-TECHNOLOGY Digest - 29 Nov 2000 to 13 Dec 2000
(#2000-3)
>
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**