Is it feasible to use both the Alko 3004 and a Bulldog 200 at the same time for added safety? The Bulldog also has the advantage of reducing the noseweight slightly because of the spring action.
Tom
Tom
Stabilisers
- Thread starter Tom_5041734
- Start date
I have seen this set before but a couple of things come to mind, is your outfit so unstable as to require 2 devices? and how does the Bulldog reduce nose weight? the spring is to reduce pitching motion in the outfit.
Hi Tom,
Mark is right, this question has been asked before and in brief:
No - it's not a good idea to use both - the tow-bar type approval process will have approved the use of one device at a time. Using two together stands the very real chance of exceeding a design specification on either the tow-ball or the tow-bar frame.
Each stabiliser applies roughly the same frictional force to resist free-rotation around the tow-ball - so doubling this force will make the coupling very stiff - and you may experience issues with towing the caravan on anything other than a straight road.
So no, don't do it.
Robert
Mark is right, this question has been asked before and in brief:
No - it's not a good idea to use both - the tow-bar type approval process will have approved the use of one device at a time. Using two together stands the very real chance of exceeding a design specification on either the tow-ball or the tow-bar frame.
Each stabiliser applies roughly the same frictional force to resist free-rotation around the tow-ball - so doubling this force will make the coupling very stiff - and you may experience issues with towing the caravan on anything other than a straight road.
So no, don't do it.
Robert
Thanks for the replies. The outfit is very stable but as I have 2 stabilisers it appeared to make sense to use them both - belt and braces I suppose. I'm now intrigued as to why Bulldog offer the 400 as it's basically 2 stabilisers, one down each side of the a-frame. I have asked them to comment but nothing so far.
Hi Tom just been on the web to look at the Bulldog 400 it appears from the intructions that it is set up with 33kg of side resistance per arm which would give you a total of 66kg resistance to the caravan stepping out of line, i think solo stabilisers are set up with more than this, the straightliner i used to use had a resistance of a 100kg,so 2 stabilisers intended for solo use would have a very high resistance to the caravan stepping out of line but also a friction stabiliser resist the caravan coming back into line, thats why the stiaghtliner was so good it positivley acts on the caravan to pull it back on a staight line, hope this helps.
The Staightliner is for sale now got a van with an Alko hitch
The Staightliner is for sale now got a van with an Alko hitch
Mark, you are correct in stating that the setting for a Bulldog 400 is 33kg on each side. However the Bulldog 200 and 300 single leaf stabilisers are only set at 27 kg!!! Strange but true! Still awaiting a response from Bulldog on this topic.
Hi Mark,
I think you'll find that the target market for the 400 "twin" is things like large boat or commercial trailers, and not a white box on wheels
Lutz reminded me that the ISO standard for caravan stabilisers sets a maximum limit of around 300 NM - that's a force of 300 Newtons applied at a distance of one metre - and converting Newtons into Kg - that's a mass of 30.6 kg applied at a distance of 1 metre.
And that's in the same ball park as the Bulldog (and AL-KO)stabiliser - where you use a set of bathroom scales (at the extreme end of the blade) to pre-set the friction pad resistance to 27 kg or 33 kg depending on model.
And yes I know the blades are a bit shorter than 1 m - but that helps comply with the ISO standard (shorter distance means the force will be lower)
Robert
I think you'll find that the target market for the 400 "twin" is things like large boat or commercial trailers, and not a white box on wheels
Lutz reminded me that the ISO standard for caravan stabilisers sets a maximum limit of around 300 NM - that's a force of 300 Newtons applied at a distance of one metre - and converting Newtons into Kg - that's a mass of 30.6 kg applied at a distance of 1 metre.
And that's in the same ball park as the Bulldog (and AL-KO)stabiliser - where you use a set of bathroom scales (at the extreme end of the blade) to pre-set the friction pad resistance to 27 kg or 33 kg depending on model.
And yes I know the blades are a bit shorter than 1 m - but that helps comply with the ISO standard (shorter distance means the force will be lower)
Robert
I don't see how that calculation works for the Alko stabiliser as it doesn't have a blade and it's not at one metre from the ball but I assume that Alko have calculated that the grip excerted by the pads is the same as approx 30kg at one metre. Getting far too complicated for me!! I'll stick with the Alko and put the Bulldog on E-bay!!
Hi Tom,
The example I showed was specifically aimed at the blade stabiliser - where Bulldog recommend using a set of bathroom scales at the end of the blade to set the "slip point".
If you have the right equipement - a tow-bll and a bar - you can do the same test on an AL-Ko, Winterhof or Westfalia - and it comes out as the same sort of value.
But with the AL-Ko you don't need to set this "slip point" yourself, it's automatically set when you close the handle.
Robert
The example I showed was specifically aimed at the blade stabiliser - where Bulldog recommend using a set of bathroom scales at the end of the blade to set the "slip point".
If you have the right equipement - a tow-bll and a bar - you can do the same test on an AL-Ko, Winterhof or Westfalia - and it comes out as the same sort of value.
But with the AL-Ko you don't need to set this "slip point" yourself, it's automatically set when you close the handle.
Robert
hi tom
I know this will be a bit controvertial but for my money use the bulldog and ditch the alko or use both, I have for a few seasons since buying a van which had the alko 300 hitch fitted as standard in my opinion the alko on its own is not up to the job.
I cannot argue with roberts comments as I do not have a degree in mathematics and base my remarks on experience alone.
however this subject has come up quite a few times and similar answers follow on but I dont understand the logic behind it? as the turning resistance of the differant types of stabiliser are exerted in a differant places ie ball and bracket
I know this will be a bit controvertial but for my money use the bulldog and ditch the alko or use both, I have for a few seasons since buying a van which had the alko 300 hitch fitted as standard in my opinion the alko on its own is not up to the job.
I cannot argue with roberts comments as I do not have a degree in mathematics and base my remarks on experience alone.
however this subject has come up quite a few times and similar answers follow on but I dont understand the logic behind it? as the turning resistance of the differant types of stabiliser are exerted in a differant places ie ball and bracket
Yes, if you have two stabilisers the torque is applied at different points on the towbar but the forces are still transferred to the vehicle underbody at the same locations where the towbar is bolted to the sheet metal.
I still go back to the example of the Bulldog 400 which is 2 blade stabilisers each set at 33kg. It shouldn't matter how heavy the trailer is, it still exerts the same forces on the car so why is the Bulldog 400 acceptable but an Alko and single Bulldog are not? Also you hear of people setting their blade stabiliser incorrectly i.e. torqueing the central bolt instead of using the bathroom scales, which gives a much higher setting probably on a par with using 2 stabilisers, but I've never heard of a car being damaged as a result. Maybe the stabiliser manufacturers and tow bar manufacturers need to produce more information on this issue.
There is an ISO standard which specifies the torque performance of integrated stabilisers like the AlKo and the towbar and car manufacturers design their products for strength and durability on that basis. Therefore, if anyone exceeds those maximum limits for any appreciable length of time there is a danger that something (probably the towbar fixing to the car underbody because that's usually the weakest link in the chain) will fail as it will be subjected to higher loads than what the components were designed for.
hi all
I dont know how your bar is fitted but mine has 10 fixing points to the car including the original suspension points which in my view is probably one of the strongest assemblies of the underbody not the weakest.
also it seems to me a bit odd is that in theory a bar that is designed to to take a tow load of say 2000kg max which includes I assume spare capacity ie safe working load and also includes a stress calculation for the said 2000kg pay load during braking ect can be damaged by adding a extra 33kg of force when towing a van that weighs 1400kg that is to say :- 2000-14000 +33 =1433 =667kg under its design strenth.
this is what I meant by I dont understand the logic behind it.
colin
I dont know how your bar is fitted but mine has 10 fixing points to the car including the original suspension points which in my view is probably one of the strongest assemblies of the underbody not the weakest.
also it seems to me a bit odd is that in theory a bar that is designed to to take a tow load of say 2000kg max which includes I assume spare capacity ie safe working load and also includes a stress calculation for the said 2000kg pay load during braking ect can be damaged by adding a extra 33kg of force when towing a van that weighs 1400kg that is to say :- 2000-14000 +33 =1433 =667kg under its design strenth.
this is what I meant by I dont understand the logic behind it.
colin
Interesting reply received from Bulldog:
"Dear Tom
Thankyou for your email.We can not see any reason why the Bulldog 200Q can not be used in conjunction with the Alko 3004 as you correctly point we manufacture a double leaf spring stabiliser which has been in production for a number of years.The main advantage of using this type of stabiliser is the reduction of pitch when in use."
Alko on the other hand do not recommend the use of 2 stabilisers but there was no technical justification for this. I suspect it may be more a marketing exercise to stop people using other manufacturers products.
In line with Colins comments, my car has a towing limit of 2800 kgs but my caravan MLTPM is 1600 kgs so surely there can be no danger in using an extra 30kgs of lateral stabiliser with the added benefit of reducing pitching to make the ride more comfortable?
Tom
"Dear Tom
Thankyou for your email.We can not see any reason why the Bulldog 200Q can not be used in conjunction with the Alko 3004 as you correctly point we manufacture a double leaf spring stabiliser which has been in production for a number of years.The main advantage of using this type of stabiliser is the reduction of pitch when in use."
Alko on the other hand do not recommend the use of 2 stabilisers but there was no technical justification for this. I suspect it may be more a marketing exercise to stop people using other manufacturers products.
In line with Colins comments, my car has a towing limit of 2800 kgs but my caravan MLTPM is 1600 kgs so surely there can be no danger in using an extra 30kgs of lateral stabiliser with the added benefit of reducing pitching to make the ride more comfortable?
Tom
I don't know what torque is equivalent to the 33kg that the Bulldog stabiliser is set to. Without this information from Bulldog it is impossible to comment as it is the total torque from two stabilisers acting together on the towball that is important, not the force.
In their reply, suggesting that that AlKo's recommendation is based only on a marketing exercise, Bulldog have obviously not even understood the potential technical problem. Otherwise, they would have made a statement accordingly.
Neither the car manufacturers nor AlKo have ever tested the durability of their products using two stabilisers, therefore AlKo's reservations are more than understandable. I doubt whether Bulldog have any data to the contrary. Their reply appears to be from a salesman as it lacks any fundamental engineering facts.
In their reply, suggesting that that AlKo's recommendation is based only on a marketing exercise, Bulldog have obviously not even understood the potential technical problem. Otherwise, they would have made a statement accordingly.
Neither the car manufacturers nor AlKo have ever tested the durability of their products using two stabilisers, therefore AlKo's reservations are more than understandable. I doubt whether Bulldog have any data to the contrary. Their reply appears to be from a salesman as it lacks any fundamental engineering facts.
hi all
intersting rely from bulldog there tom although not backed up by any technical criteria and of course a vested interest in consumers using their products it does give some indication that a least the possibility of using two sabilizers may not be a unsound practice and could have beneficial results.
since my last post I have trawled through the web pages of manufacturers and saftey web sites but can not find any reference to the use of two stabilizers apart from one north american towbar equipment manufacturer that supply a double blade canilever stablizer for use with boats and one man tow equipment and according to them reduces the side shift strain and increases trailer stability it looks similar to the two blade bull dog with a bar in between them but does not give any technical data of how it works or why??.
ok so one has to bear in mind that the us and canada have thousands of miles of dead srraight roads and no counrty lanes to negotiate however at least with belt and braces your trousers wont fall down so with out any concrete evidence to the contarary I for one will continue to use the old scott blade and the alko together in certainty that a very least when on a windy M5 when hgvs go thundering past it will have no effect on the van.
I shall of course bear in mind roberts and lutz's resevations and check the bar and mounting points at very least once a year but up to now have found no problems and can not really forsee any dificulties as we are only talking about 30kg exra side strain on equipment designed to take far greater trailer weights than the 1100 kg that I put on it.
bye for now keep me posted if any futher information comes to light as this is a interesting subject.
colin
intersting rely from bulldog there tom although not backed up by any technical criteria and of course a vested interest in consumers using their products it does give some indication that a least the possibility of using two sabilizers may not be a unsound practice and could have beneficial results.
since my last post I have trawled through the web pages of manufacturers and saftey web sites but can not find any reference to the use of two stabilizers apart from one north american towbar equipment manufacturer that supply a double blade canilever stablizer for use with boats and one man tow equipment and according to them reduces the side shift strain and increases trailer stability it looks similar to the two blade bull dog with a bar in between them but does not give any technical data of how it works or why??.
ok so one has to bear in mind that the us and canada have thousands of miles of dead srraight roads and no counrty lanes to negotiate however at least with belt and braces your trousers wont fall down so with out any concrete evidence to the contarary I for one will continue to use the old scott blade and the alko together in certainty that a very least when on a windy M5 when hgvs go thundering past it will have no effect on the van.
I shall of course bear in mind roberts and lutz's resevations and check the bar and mounting points at very least once a year but up to now have found no problems and can not really forsee any dificulties as we are only talking about 30kg exra side strain on equipment designed to take far greater trailer weights than the 1100 kg that I put on it.
bye for now keep me posted if any futher information comes to light as this is a interesting subject.
colin
It's not 30kg side strain, it's probably around 300Nm of additional torque as well as the side forces acting on the coupling, for example due to crosswind buffeting the caravan sideways. How the towbar and vehicle underbody withstands the 2 million cycles specified by law under these more severe conditions is unknown. It may or may not be a problem and it may only apply to certain configurations. The truth is nobody has the answer.
Certainly seems to have opened a can of worms!! I think Lutz is correct in saying nobody knows the answer and until the manufacturers do some proper testing it will remain that way. I have never heard of an accident or incident which has been blamed on the use of 2 stabilisers but will check with both my car insurer and caravan insurer for their approval. Probably time to put this one to bed!!
There's absolutely no danger of 2 stabilisers causing an accident and only in very extreme cases is it even conceivable that they may be a safety hazard. What could possibly happen, however, is material failure, most likely sheet metal cracks in the area of the towbar attachment points. As these are under the car, the problem may go unnoticed for a considerable length of time.
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