Question for the physics experts : Rolling load of a trailer..

[reeac]

As a retired physicist I feel that I should make a contribution. I see no way that you can calculate the total effort required to move that trailer - the problem is the rolling friction component which is dependant on too many factors such as tyre design and pressure and surface texture of the drive. Best way to get a feel for effort required would be to borrow a big spring balance and get enough people or else a compact tractor to pull a rope until the trailer moves - particularly at the point where there is the slight slope. As an alternative to the spring balance rig up a pulley or block lashed or shackled to something (a tree or vehicle) at waist level and then run the tow line horizontally through it and then downwards culminating in a loop which you can stand in - see if your weight can move the trailer. In short: measure the force rather than trying to calculate it. Once you know the required force you'll be in a better position to choose a method that will work without being over the top.

 

[Iliade]

Having established the maximum load during the pull (perhaps use a spring balance and a lever) you could replace the nasty scary thick wire with dyneema. It could be much thinner than the winch wire as it would need to be far lower breaking strain and thus you could get a lot more on the drum.

E.g we have a 100m (50m?) reel of 240kg dyneema that is about 5"*3"

Dyneema lasts and handles well, to all intent & purpose doesn't fatigue fail. The only issue is it is thin enough to cause harm if you wrap it around your hand and pull! (also use a very serpentine knot since at high loads it will creep)

 

[wipe_out]

Thanks for all the input and suggestions..

I understand the problem of the unknown factors of the friction of the wheels and surface etc.. The spring test and actually measuring is a good idea.. I don't have the boat yet unfortunately (will be here in July) which is why the guess work.. Maybe my car would work as a test object which according to Parkers it weighs 2530 kg and also has 4 wheels so should (??) give a close enough number to determine the winch power needed.. Just have to track down a big spring scale..

 

[Lakesailor]

You are all over-thinking the matter. Dyneema? Electric winches?
Just use whatever you have to hand or learn to reverse.

 

[Hadenough]

http://www.watling-towbars.co.uk/launching_boats.html

 

[lw395]

......
I'd be tempted to find an old sheet winch (Lewmar 8 or similar) then install it on the trailer just behind the towball/tongue. More than enough power to pull the trailer up a ramp, and importantly, you can surge the line under control to let the trailer down the ramp.

I loaned someone an old dinghy ratchet block to assist with hauling a dory trailer to his towball. That worked OK except in the sense I never got the block back.

 

[wipe_out]

You are all over-thinking the matter. Dyneema? Electric winches?
Just use whatever you have to hand or learn to reverse.

The issue is that I have to make it 15m where the gap is about 3m wide (boat is 2.55) and at the pinch point will have about 20mm clearance each side.. I will never be that accurate when reversing.. Having a winch to provide the power and then steering from the hitch slowly will be far safer.. That is all assuming I can get the bow rails to come in under the sofits by dropping the front of the trailer as low as it can go on the jockey wheel.. If it doesn't clear I am probably looking at 40-50mm clearance each side for the whole 15m..

 

[Avocet]

Thanks for all the input and suggestions..

I understand the problem of the unknown factors of the friction of the wheels and surface etc.. The spring test and actually measuring is a good idea.. I don't have the boat yet unfortunately (will be here in July) which is why the guess work.. Maybe my car would work as a test object which according to Parkers it weighs 2530 kg and also has 4 wheels so should (??) give a close enough number to determine the winch power needed.. Just have to track down a big spring scale..

Yes, that's an excellent idea. The rolling resistance of your car won't be so different at all. As plenty of others have said, it's a surprisingly small force that you need to exert though. More of an issue will be trailer stability. On occasions when I've pushed trailers around with a load on them, the jockey wheels tend to be the first things to give out - especially if they hit a joint between paving stones or a pothole. Also, when "lowering" it back down the drive, you'll need help steering the trailer or it will take on a mind of it's own!

Just thinking outside the box though, have you thought of using a caravan mover?

Expensive ones here:

http://www.caravanmoversonline.co.uk/

Cheaper one here:

http://www.ebay.co.uk/itm/Mr-Shifta...017?pt=LH_DefaultDomain_3&hash=item3f4d3e2cf1

 

[ufans]

This might help, used in the vehicle recovery industry

https://cdn.shptrn.com/media/mfg/43...ngTechniquesforVehicleRecovery.pdf?1314391730

 

[lw395]

Yes, that's an excellent idea. The rolling resistance of your car won't be so different at all. As plenty of others have said, it's a surprisingly small force that you need to exert though. More of an issue will be trailer stability. On occasions when I've pushed trailers around with a load on them, the jockey wheels tend to be the first things to give out - especially if they hit a joint between paving stones or a pothole. Also, when "lowering" it back down the drive, you'll need help steering the trailer or it will take on a mind of it's own!

Just thinking outside the box though, have you thought of using a caravan mover?

]

I did suggest that.
I was not aware of this sort, which seems to be mains powered?
http://www.ebay.co.uk/itm/Motor-Mov...6&pid=100005&rk=1&rkt=6&sd=271878860017&rt=nc

The advantage of these over 'learn to reverse' is that you can move the tow hitch in any direction.