Motor mover slippage

[Lutz]

What sort of experience do other users of motor movers have of their performance on wet soggy ground? My single axle 1800kg has a Truma motor mover fitted and failed to shift it on a muddy pitch because the drive was slipping against the tyres. It's my first caravan to have a motor mover fitted so I was wondering whether this is normal under adverse conditions like these, or what sort of conditions one can expect a motor mover to be capable of handling.

(I presume that the mover itself was adjusted properly by the dealer who fitted it and that the slippage was not due to maladjustment)

 

[nrdonnelly]

Lutz,

A lot of these sort of problems are caused by low tyre pressure. The tyre pressures are critical in ensuring good traction between roller and tyre, particularly in high-slip conditions such as you describe. It's much easier to check before getting the installation adjusted!

Hope this helps

Nigel Donnelly

Editor

Practical Caravan

www.twitter.com/pcaravan

 

[WatsonJohnG]

Usually a spacer is provided with the mover and its easy to insert it between the tyre and roller to check if its set right

I have needed to reset mine a few times over the years as the pressure needed on the tyre can cause the unit to creep along the chassis

 

[JTQ]

With a cast alloy Powrtouch 3, fitted on a 1900 kg s/a van and both the tyre pressure and gap set correctly we can get slippage in difficult conditions.

Such as wet tyre, wheel sunk in ground etc. It helps sometimes to ease the van out a tyre at a time where you can "assist" by pushing sideways on the hitch.

Our earlier Reich with an embedded grit type roller and lighter 1700 kg s/a van was a bit less prone to slipping but far from immune.

I accept that traction is limited with these devices and will be a bit more of an issue in wet conditions with heavy vans.

I have no experience of the drive limits with castellated rollers, and wondered myself how these compare with friction drives.

 

[Dustydog]

Our heavyduty Twin Powrtouch has needed adjustment once in the last two years. It seems to me the Powrtouch rollers are more robust with better grips than the FIL's Truma.

We have had wheel slip, not the Powrtouch, but the wheel itself! Clearly we need a traction control system.LOL.

It sounds like you need some adjustments made to the tensions on the traction motors to tyres. As John Watson says the distance between the rollers and tyres is important as is the tyre pressure. Initially I was quite surprised just how far "in "the rollers went into the tyres.

Cheers

Dustydog

 

[JTQ]

With the Twin Powrtouch of course the rollers are only coping with about half the torque faced by the single axle so slippage will be very different.

Also the twin axle has a greater footprint so settling into the damp ground will less than for a single axle requiring torque overall. This is something that also must help twin axle owners with only two wheel drives relative to similar weight single axle vans.

 

[JTQ]

With the Twin Powrtouch of course the rollers are only coping with about half the torque faced by the single axle so slippage will be very different.

Also the twin axle has a greater footprint so settling into the damp ground will less than for a single axle requiring torque overall. This is something that also must help twin axle owners with only two wheel drives relative to similar weight single axle vans.

Edit:

"Also the twin axle has a greater footprint so settling into the damp ground will less than for a single axle requiring lower torque overall".

 

[Dustydog]

Edit:

"Also the twin axle has a greater footprint so settling into the damp ground will less than for a single axle requiring lower torque overall".

The Powrtouch Twin I have only works on two wheels not four as with the Powrtouch All Wheel Drive Twin. The motors are specifically geared down to apply more torque to the wheels because of the additional weight that requires moving. I guess that's why "wheelspin " can be achieved in certain circumstances.

Are we talking at cross purposes here JTQ? My apologies now if I have misunderstood your point.

Cheers

Dustydog

 

[Gumbo]

No real problem on wet ground witha Truma TE, the real problem comes for us on sites with small chippings then we do get slip.

 

[Saladdodger]

Lutz,

A lot of these sort of problems are caused by low tyre pressure. The tyre pressures are critical in ensuring good traction between roller and tyre, particularly in high-slip conditions such as you describe. It's much easier to check before getting the installation adjusted!

Hope this helps

Nigel Donnelly

Editor

Practical Caravan

www.twitter.com/pcaravan

Nigel

Do you think Lutz would have incorrect tyre pressures?

 

[C_374479958]

Perhaps the slippage is caused by the smooth ribbed Truma mover wheel, where as the Powrtouch is a Knobbly spikey wheel, not sure what damage it may do to the tyre though if IT slipped.

 

[Dustydog]

The Powrtouch Twin I have only works on two wheels not four as with the Powrtouch All Wheel Drive Twin. The motors are specifically geared down to apply more torque to the wheels because of the additional weight that requires moving. I guess that's why "wheelspin " can be achieved in certain circumstances.

Are we talking at cross purposes here JTQ? My apologies now if I have misunderstood your point.

Cheers

Dustydog

 

[JTQ]

Dustydog:

Well I made an error in assuming that the "Twin" was the four-wheel drive unit; my "half torque" comment [at the roller/tyre] was about movers driving on both axles, sorry.

The same higher geared drive unit is also supplied as the "heavy duty 3" for the single axle market but here fitted with a smaller roller that further increases its overall gearing. My single axle van is up at twin axle weights, being 1900kg. I had a dialog with them because of its weight and the recommendation was to have the smaller roller version. I never did understand why in the twin axle case they fit a larger roller.

The original units I was supplied with had cast alloy rollers with "spikes" but the replacement for some reason had cast large "diamond knurl" surface. I feel the spikes might have given better wet traction than the smoother surfaced diamonds.

Mine never gets any "wheel-spin", but gets a lot of roller to tyre slip in wet conditions. The smooth diamond knurl does not leave any visual witness on the tyre after slipping. Never got to try the spiked rollers in the wet.

I can see with a twin axle van with drive to a single axle it could more easily encounter wheel spin. And I can see that for the same weight the twin axle could roll easier on soft ground.[in straight line anyway]

Lutz's Truma unit with its big castellated pattern might present too smooth a surface to be good in the wet. Wet rubber against metal has zilch friction [used in marine shaft bearings] , so any drive must be through its ability to deform the rubber.

As I said in an earlier posting I am interested in how well this type of roller actually performs in the wet, Lutz's experience is suggesting no better than my diamond knurl.

Cheers JTQ

 

[Dustydog]

JTQ

I also have the diamond knurl rollers which are very "rugged" imo. I think they are the standard roller diameter. When I was buying the dealer and Powrtouch told me the Powrtouch Twin was more than sufficient for the Wyoming as there was a heavier duty motor and the gearbox lowered the overall ratio giving plenty of torque.

I could have gone for the four wheel drive version but felt the extra expense and bother of moving the spare wheel and carrier , pipe work and extra weight wasn't worth it.

The rollers do intent quite a lot into the tyres and have never slipped on the tyre. I have had the wheel spin on very wet grass caused mainly by the jockey wheel sinking in the mud.

I use a wide , solid jockey wheel. I am certain that also influences the overall performance.

Cheers

Dustydog

 

[Gafferbill]

Lutz has a single axle 1800kg caravan, which no doubt contributed to the mover slipping....... in the soft ground the rolling resistance would have increased enormously due to almost 900kg on each wheel... I am not mentioning what happened to the jockey wheel.

My concern about movers is that some people move caravans up slopes with them expecting the mover to provide the braking and not realising the roller can slip against the tyre!

 

[WatsonJohnG]

I remeber you expressing that concern before

In my experience they do hold well on quite steep slopes but under muddy/ wet conditions it would be wise to use chocks as well

I use them a little in front of the wheel just in case when pausing in manoevering the van on my tarmac drive even in the dry

I once last year had the van run away in reverse as the brakes were inadequate and the handy chock saved serious damage

 

[trucker]

Used the powrtouch now for 5 years and caravan all year round, never had any slippage in any condition, this is the heavy duty 3 on a 1450kg caravan

Kevin

 

[Gafferbill]

........ I have been fitting my seat belt ever since Jimmy Savill told me to "clunk click" it has never worked in anger...it is a safety back up!

There is a potential danger with a caravan on a slope when using a mover... it is wise to have a back up.

Watson(JohnG) uses chocks as his back up.