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theodon

trailer with surge brakes

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theodon    0

I need to tow a 23ft cruiser boat on the public road. My trailer has surge brakes. DO you guys use a weight distribution hitch like the blue ox towing WDH? I'm hearing conflicting reports on this. I was told that it is not ideal to use a WDH since I have surge brakes on my trailer and the hitch will put to much force on the tongue. Is this true? Any advice/suggestions will be much appreciated. Thanks! 

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cuthound Contributor    371

This thread shows what can happen if the noseweight is too low. 

IIRC, the trailer designer I was working with, said that ideally nose weight should be 4% of the trailers gross weight, i. e. about 140kg on at 3500kg trailer.

 

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Iain_S    77

Not too sure how that device functions!

When we towed Gamebird, we used twin stabilisers. Noseweight was fairly high, probably above the optimum, and I found it surprising how much a small change in weight distribution within the boat could affect the handling, although some of that could have been psychological! 

The stabilisers certainly helped, allowing an extra 10 m.p.h. or so, which meant we could keep up with the trucks, making the journey a bit more relaxing, wtihout being overtaken by HGVs every five minutes!

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Graham Davis    326
9 hours ago, theodon said:

I need to tow a 23ft cruiser boat on the public road. My trailer has surge brakes. DO you guys use a weight distribution hitch like the blue ox towing WDH? I'm hearing conflicting reports on this. I was told that it is not ideal to use a WDH since I have surge brakes on my trailer and the hitch will put to much force on the tongue. Is this true? Any advice/suggestions will be much appreciated. Thanks! 

As that is an American site, I'm not even sure if they would be legal in the UK.

And what are "surge brakes"? I've been towing for 40+ years and never heard of them.

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cuthound Contributor    371
40 minutes ago, Graham Davis said:

And what are "surge brakes"? I've been towing for 40+ years and never heard of them.

I suspect he means "overrun brakes".

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nicknorman    1,972

In my opinion it's a (very popular) myth to say that having lots of nose weight makes a combination more stable. If there is a lot of weight in the nose, when the combination corners (or starts a weave) the towbar pushes the rear of the car in the opposite direction giving a tendency to "oversteer", and eventually in extremes to jackknife.

In my experience of towing numerous glider trailers (which tend to be very long) the combination is most stable when there is minimal weight on the tow bar. But obviously one doesn't want negative weight on the towbar.

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cuthound Contributor    371
15 minutes ago, nicknorman said:

In my opinion it's a (very popular) myth to say that having lots of nose weight makes a combination more stable. If there is a lot of weight in the nose, when the combination corners (or starts a weave) the towbar pushes the rear of the car in the opposite direction giving a tendency to "oversteer", and eventually in extremes to jackknife.

In my experience of towing numerous glider trailers (which tend to be very long) the combination is most stable when there is minimal weight on the tow bar. But obviously one doesn't want negative weight on the towbar.

Definately not the case for the mobile generators I tested.

When I hired Bruntingthorpe Vehicle Test Facilty to test the stability of the 3500kg mobile generators,  we moved from absolute balance (no nose weight at all, to 150kg nose weight (the maximum recommended for the Land Rover Defender tow vehicle) over several steps.

The rig circulated their track at a steady 50mph, whilst being overtaken by a 44 tonne artic at 56mpg, a 7.5 tonner circulating at 70mph and several people testing racing cars at very high speeds.

Each increment of increased nose weight improved stability and reduced "snaking time".

The trailer designer said 4% was the theoretical ideal nose weight, (140kg for a 3500kg trailer) and we couldn't go over 150kg, so unable to test the impact of too much nose weight.

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Graham Davis    326
3 hours ago, cuthound said:

I suspect he means "overrun brakes".

I did wonder that, but considering that the link was to an American site, and the American towing systems can be very different, it needs clarifying.

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jake_crew    14

I certainly agree that the original post sounds American.

I imagine the laws about towing are different in the USA to here in the UK, so best to check wherever you live Theodon.

However, the usual reccomendation that the towing vehicle shuld be significantly heavier than the trailer & boat seems like very good Universal Physics & Engineering to me.

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nicknorman    1,972
16 hours ago, cuthound said:

Definately not the case for the mobile generators I tested.

When I hired Bruntingthorpe Vehicle Test Facilty to test the stability of the 3500kg mobile generators,  we moved from absolute balance (no nose weight at all, to 150kg nose weight (the maximum recommended for the Land Rover Defender tow vehicle) over several steps.

The rig circulated their track at a steady 50mph, whilst being overtaken by a 44 tonne artic at 56mpg, a 7.5 tonner circulating at 70mph and several people testing racing cars at very high speeds.

Each increment of increased nose weight improved stability and reduced "snaking time".

The trailer designer said 4% was the theoretical ideal nose weight, (140kg for a 3500kg trailer) and we couldn't go over 150kg, so unable to test the impact of too much nose weight.

Perhaps it depends on how the mass is distributed rather than the relationship between the axle and the centre of gravity? Glider trailers are pretty long for the mass, I can imagine a generator being much shorter thus with a smaller radius of gyration. It will also depend on the towing vehicle since the instability I refer to arises from the trailer affecting the vehicle, rather than the trailer's stability in its own right.

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cuthound Contributor    371
8 minutes ago, nicknorman said:

Perhaps it depends on how the mass is distributed rather than the relationship between the axle and the centre of gravity? Glider trailers are pretty long for the mass, I can imagine a generator being much shorter thus with a smaller radius of gyration. It will also depend on the towing vehicle since the instability I refer to arises from the trailer affecting the vehicle, rather than the trailer's stability in its own right.

Very possibly, I had no experience of towing until that, indeed my first experience was with towing the generator with zero nose weight! 

The Land Rover has a height adjustable hitch and that made a difference to stability too. It was most stable when set to the natural height of the towbar on the trailer ( a twin close coupled axle jobbie).

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Alan de Enfield    1,068
16 hours ago, cuthound said:

The trailer designer said 4% was the theoretical ideal nose weight, (140kg for a 3500kg trailer) and we couldn't go over 150kg, so unable to test the impact of too much nose weight.

My Mercedes M-Type has a max trailer nose weight of 150kgs, but our Tri-Axle 3500kg Horse Trailer (it has 'living' in the front and is 23 feet long) has a nose weight in excess of 220 kg (the max weight limit of the scales is 22kg) and tows superbly. The weight of the horse(s) is directly over the axles so makes little difference to the 'balance'.

I have (for many years) towed 30 foot Glider trailers all over the country, and being so light and only single axle are relatively easy to 'pull back in line' if they do start to 'wander', but I have seen the odd one or two on the side of the A1 in a bit of a crumpled heap.

I think the additional driving test requirements for trailers should help the ab-initio to better understand what they are doing.

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nicknorman    1,972
1 hour ago, Alan de Enfield said:

I have (for many years) towed 30 foot Glider trailers all over the country, and being so light and only single axle are relatively easy to 'pull back in line' if they do start to 'wander', but I have seen the odd one or two on the side of the A1 in a bit of a crumpled heap.

Yes single seater trailers tend to be pretty light. However my ASH25 weighs 550kg and the metal trailer it's in is long and heavy, double axle, and starts to weave over about 65.

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Alan de Enfield    1,068
3 minutes ago, nicknorman said:

Yes single seater trailers tend to be pretty light. However my ASH25 weighs 550kg and the metal trailer it's in is long and heavy, double axle, and starts to weave over about 65.

I had a Skylark 3F at around 830lbs then an IS29D which weighed in at 240kg

We would have a 'Winter expedition' to Sutton Bank over the Christmas period and take a mix of gliders K6, Astir, my IS29 and the club IS28 - that was a pretty heavy beast at about 400kg empty weight but pales into insignificance to your ASH25 at 550Kg.

Ahhhh - A convoy of Gliders from Saltby to Sutton Bank, struggling in the snow up the 'bank' and around the hairpins, those were the days !!

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bizzard    874

The longer the wheelbase of the towing vehicle the more stable the combo will be. The old Volvo 240's were good towers.

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RLWP    1,038
4 hours ago, nicknorman said:

Perhaps it depends on how the mass is distributed rather than the relationship between the axle and the centre of gravity? 

It does. I used an 8' x 4' trailer to move two electric cement mixers. Moving them to the job, I had them strapped together in the middle over the axle. On the return I had one at each end of the trailer. With them at the ends, the trailer became unstable and snaked easily. 

I moved the mixers back to the middle and it was fine again. Nose weight and overall weight were the same

Richard

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cuthound Contributor    371

Photos of the rolled over mobile generator, and an undamaged one with a Land rover

100kVA Canopy Front.JPG

100kVA ACM and Land Rover 4.JPG

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nebulae    25

A tri axle is much more stable at speed than a twin axle. 3,500kg Ifor Williams behind a Discovery with a max gross loading and 150kg nose weight is comfortable at 50mph,in my experience. At 55 a passing lorry or a gust of wind can seriously unsettle the rig. As to the over run brakes,if the braking of the towing vehicle is not effective,then the trailer brakes will not come on. I have had many linen soiling moments where the rig does not respond predictably to my efforts to stop. American trailers have electric braking(From the towing vehicle) or no brakes at all. Dont know what the parameters are for over run brakes in the States.

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mrsmelly Contributor    1,247
11 hours ago, nicknorman said:

Yes single seater trailers tend to be pretty light. However my ASH25 weighs 550kg and the metal trailer it's in is long and heavy, double axle, and starts to weave over about 65.

Which is of course why the speed limit for towing is 50/60 mph :rolleyes:

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nicknorman    1,972
9 hours ago, mrsmelly said:

Which is of course why the speed limit for towing is 50/60 mph :rolleyes:

No it isn't. If the towing speed limit was based on a propensity to weave, there would be just one figure, not two.

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mrsmelly Contributor    1,247
57 minutes ago, nicknorman said:

No it isn't. If the towing speed limit was based on a propensity to weave, there would be just one figure, not two.

I havnt time to educate you on the whys and wherfors of the speed limits on public roads your knowledge and driving experience and training is too far below mine to have a meaningful debate. The speed limit is 50/60 for a reason playing on words doesn't wash. Basicaly you shouldn't even know that yours starts to weave above 65 mph as you aren't equipped to deal with it at that speed.

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nicknorman    1,972
50 minutes ago, mrsmelly said:

I havnt time to educate you on the whys and wherfors of the speed limits on public roads your knowledge and driving experience and training is too far below mine to have a meaningful debate. The speed limit is 50/60 for a reason playing on words doesn't wash. Basicaly you shouldn't even know that yours starts to weave above 65 mph as you aren't equipped to deal with it at that speed.

Oh you are so parochial! Other countries have different speed limits! My single seater wooden Ventus trailer could easily do 80. I say "could" because it's now trashed.

No, not from some terminal weave but from Mother Nature who decided to pick it up from the trailer park and deposit it upside down in the hedge. So no point in bothering with speed limits when your trailer's going to get trashed anyway.

As to your superior driving knowledge and experience, operating in 2 dimensions is so trivially easy. Operating in 3 dimensions adds a whole other ... dimension!

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mrsmelly Contributor    1,247
25 minutes ago, nicknorman said:

Oh you are so parochial! Other countries have different speed limits! My single seater wooden Ventus trailer could easily do 80. I say "could" because it's now trashed.

No, not from some terminal weave but from Mother Nature who decided to pick it up from the trailer park and deposit it upside down in the hedge. So no point in bothering with speed limits when your trailer's going to get trashed anyway.

As to your superior driving knowledge and experience, operating in 2 dimensions is so trivially easy. Operating in 3 dimensions adds a whole other ... dimension!

Oy Nick that took you 8 minutes longer than I thought it would :lol: and too true Flying them copter jobbies is for the criminaly insane, well insane anyway, fair play to you :cheers:

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