On our last trip, the OH spotted an outfit that had two stabilsers, both the hitch type and blade fitted to the same van.
Isn't that a bit overkill ?
Isn't that a bit overkill ?
Two Stabilsers !!
- Thread starter Rubix
- Start date
I presume you mean 2 frictional type stabilisers, in which case the short answer is yes.
Theoretically, a stiffer joint, which, in effect, these stabilisers provide, would improve stability. However, neither the towbars nor the car underbody to which the towbar is attached are designed for this condition. ISO Standards define a maximum stiffness and both car and towbar manufacturers use this figure for their design and test purposes. Therefore, neither the car nor the towbar manufacturer can guarantee that any further increase as a result of a second stabiliser may not result in the risk of reduced durability of the components, i.e. failure at some time in the future.
The only type of supplementary stabiliser which can be used without such risk is one which does not impose higher loads through the towball. This would be an electronic one, like the AlKo ATC or the BPW IDC.
Theoretically, a stiffer joint, which, in effect, these stabilisers provide, would improve stability. However, neither the towbars nor the car underbody to which the towbar is attached are designed for this condition. ISO Standards define a maximum stiffness and both car and towbar manufacturers use this figure for their design and test purposes. Therefore, neither the car nor the towbar manufacturer can guarantee that any further increase as a result of a second stabiliser may not result in the risk of reduced durability of the components, i.e. failure at some time in the future.
The only type of supplementary stabiliser which can be used without such risk is one which does not impose higher loads through the towball. This would be an electronic one, like the AlKo ATC or the BPW IDC.
hi jeff
where were you and when cos it could have been me, thats the set up I use. overkill probably but it works just fine the blade does most of the work and adds a bit of assistance to the rear springs that elliminates pitching alltogether the alko although only just set (1 click) makes sure there is no movement in high winds and vortexes from hgv's. it may look odd to some but it suits me just fine, AND:-
while lutz might have a point in theory, but thats all it is, a theory, I had what I believe was the diminutive answer from a professor of mechanical engineering in a answer posted on another forum, that was:-
"while it is true that the extra rotational force that two fricton stabilisers put on the tow ball will be significantly greater than one it is unlikley that a failure will occure in either short or long term use.
there are several reason why I say this. first, in order to gain type approval for a tow bar the manufacturer has to prove that the materials used in the bar and car underbody will withstand loads and forces far greater than the ratings to which the bar is approved for, typicaly 50 to 100% greater as a safety margin the safe working load has to take into account the maximum trailer weight that the car will tow, plus the kinetic energy sustained while braking and accelerating both horizontally and vertically. also two well adjusted friction stabilisers may well put less strain on a towbar than one poorly adjusted one, a typical rotational force of a well adjusted stabiliser is in the order of 30/35 kg a poorly adjusted one could be over 100kg but this figure would still be within the paramiters of the specifications.
other factors have a bigger effect on the performance of any towbar,the condition and age of the donor vehicle as well as ambient temperature. the scenario you posted ie: under weight van lightly loaded with two stabilisers would I believe not be outside the paramiters of the type approval and therefore acceptable.
well that was good enough for me,
colin
where were you and when cos it could have been me, thats the set up I use. overkill probably but it works just fine the blade does most of the work and adds a bit of assistance to the rear springs that elliminates pitching alltogether the alko although only just set (1 click) makes sure there is no movement in high winds and vortexes from hgv's. it may look odd to some but it suits me just fine, AND:-
while lutz might have a point in theory, but thats all it is, a theory, I had what I believe was the diminutive answer from a professor of mechanical engineering in a answer posted on another forum, that was:-
"while it is true that the extra rotational force that two fricton stabilisers put on the tow ball will be significantly greater than one it is unlikley that a failure will occure in either short or long term use.
there are several reason why I say this. first, in order to gain type approval for a tow bar the manufacturer has to prove that the materials used in the bar and car underbody will withstand loads and forces far greater than the ratings to which the bar is approved for, typicaly 50 to 100% greater as a safety margin the safe working load has to take into account the maximum trailer weight that the car will tow, plus the kinetic energy sustained while braking and accelerating both horizontally and vertically. also two well adjusted friction stabilisers may well put less strain on a towbar than one poorly adjusted one, a typical rotational force of a well adjusted stabiliser is in the order of 30/35 kg a poorly adjusted one could be over 100kg but this figure would still be within the paramiters of the specifications.
other factors have a bigger effect on the performance of any towbar,the condition and age of the donor vehicle as well as ambient temperature. the scenario you posted ie: under weight van lightly loaded with two stabilisers would I believe not be outside the paramiters of the type approval and therefore acceptable.
well that was good enough for me,
colin
Hello Jeff,
No one should rely on a manually activated stabiliser to make a trailer stable enough to tow. If an outfit cannot be towed safely without a stabiliser then it could be construed as not roadworthy. The reason is, as it requires a positive manual activity to apply the device, then it can conceivably forgotten, or not applied correctly.
A friction stabiliser should only be used to give a belt and braces approach to safety,not to provide the minimum safety to allow a system to be towed.
I do not know what the actual law is regarding multiple attachments but if it says only onecan be used, then one and no more it would be. Therefore Colin's professors pronouncement would not override any legal requirements.
Disregarding any potential legal implications, and given the circumstances of an Alko and a blade type as fitted, as the Alko and the blade do not use initial any common load bearing structures. The Alko uses the hitch and the ball, and the blade uses a separate friction plate mounting, and blade saddle. As a a consequence the two devices do not affect each other, but of course they do both have common secondary mounting assemblies, such as the caravan A frame, and the ball sub frame.
Whilst the dynamic forces generated a trailer are substantial, the low frequency high amplitude pitch and yaw motions are only likely to generate 1 to 2G, but what is often forgotten is higher band frequencies from harmonics and other sources have been measured as high as 8G (Belgian Pave) but these are very low amplitude and very short duration, but they all stress the hitch assembly. These forces are variable and highly dependant on the speed of travel, and clearly by historic evidence hitch designs seem capable of handling these.
By contrast, the forces generated by the friction devices are not dependant on speed, only on the relative turning between the trailer and the tow car. The peak forces are quite constant, and low speed. By comparison to the peak loads generated by towing, the frictional resistive forces are low, and should be easily managed by the hitch sub assemblies. Even doubling them up as in Colin's method it is unlikely in my view they will overload the assemblies.
This does not mean I endorse multiple frictional stabilisers, if it infringes any regulations
No one should rely on a manually activated stabiliser to make a trailer stable enough to tow. If an outfit cannot be towed safely without a stabiliser then it could be construed as not roadworthy. The reason is, as it requires a positive manual activity to apply the device, then it can conceivably forgotten, or not applied correctly.
A friction stabiliser should only be used to give a belt and braces approach to safety,not to provide the minimum safety to allow a system to be towed.
I do not know what the actual law is regarding multiple attachments but if it says only onecan be used, then one and no more it would be. Therefore Colin's professors pronouncement would not override any legal requirements.
Disregarding any potential legal implications, and given the circumstances of an Alko and a blade type as fitted, as the Alko and the blade do not use initial any common load bearing structures. The Alko uses the hitch and the ball, and the blade uses a separate friction plate mounting, and blade saddle. As a a consequence the two devices do not affect each other, but of course they do both have common secondary mounting assemblies, such as the caravan A frame, and the ball sub frame.
Whilst the dynamic forces generated a trailer are substantial, the low frequency high amplitude pitch and yaw motions are only likely to generate 1 to 2G, but what is often forgotten is higher band frequencies from harmonics and other sources have been measured as high as 8G (Belgian Pave) but these are very low amplitude and very short duration, but they all stress the hitch assembly. These forces are variable and highly dependant on the speed of travel, and clearly by historic evidence hitch designs seem capable of handling these.
By contrast, the forces generated by the friction devices are not dependant on speed, only on the relative turning between the trailer and the tow car. The peak forces are quite constant, and low speed. By comparison to the peak loads generated by towing, the frictional resistive forces are low, and should be easily managed by the hitch sub assemblies. Even doubling them up as in Colin's method it is unlikely in my view they will overload the assemblies.
This does not mean I endorse multiple frictional stabilisers, if it infringes any regulations
I'm not saying that either the towbar or the vehicle attachment points will fail if two frictional stabilisers are fitted. However, I am saying that they will increase the risk of failure and neither the car and towbar manufacturers would accept responsibility for any possible consequences.
I know of one particular case where the vehicle underbody sheet metal developed a crack after the car had been towing with two stabilisers over a significant period of time. This led to rust occuring at the crack. The car manufacturer refused to pay for the cost of the repair.
I know of one particular case where the vehicle underbody sheet metal developed a crack after the car had been towing with two stabilisers over a significant period of time. This led to rust occuring at the crack. The car manufacturer refused to pay for the cost of the repair.
Scott market a twin stabiliser with a double bracket
I had a Straightliner stabiliser and liked it so much that I continued to use it alongside the Alko hitch type
Then it came up as a topic on here so I asked Alko and their reply was that it would put too much strain on the towball
I wasn't convinced but having asked I had to take their advice
I now just use the Alko hitch stabiliser mainly because its so easy to use
Funny how this ties up with the other posting about towball strength on this section.
I had a Straightliner stabiliser and liked it so much that I continued to use it alongside the Alko hitch type
Then it came up as a topic on here so I asked Alko and their reply was that it would put too much strain on the towball
I wasn't convinced but having asked I had to take their advice
I now just use the Alko hitch stabiliser mainly because its so easy to use
Funny how this ties up with the other posting about towball strength on this section.
Bulldog may offer a twin arrangement, but it's unlikely whether they would take the responsibility for any possible collateral damage. Maybe a twin stabiliser is OK for a 4x4 with a beefy chassis frame but who knows whether it's still alright for all light saloon cars? There is no performance standard for blade-type stabilisers like the ISO11555-1 which applies to integrated units and I doubt whether any performance data for their product is available. I also doubt whether they ever checked with the car industry regarding its suitability. Therefore, no third party will take responsibility and you are completely on your own if you use such a stabiliser.
hi all
lutz, I think you may be over playing things a bit and making it more complicated than it needs to be, why should a third party have to take resposibility for something that you or I choose to do I guess that has more to do with the(I am not to blame so someone else must be) culture that abounds in todays world.
you said "I know of one particular case where the vehicle underbody sheet metal developed a crack after the car had been towing with two stabilisers over a significant period of time. This led to rust occuring at the crack. The car manufacturer refused to pay for the cost of the repair".
just assuming that a particular problem was caused only by one factor is to my mind flawed and without subtance, for instance how old was the car??, how long had it been used for towing??, what size trailer was it??, was the overun damper working??,what else had the car towed during it's life had it towed another car??, or pulled up tree roots ECT??, you see what I am getting at!!.
my doctor once told me that my bad chest was due to smoking!! ok I said but what about the 20 odd years I did down the pit and all the black stuff I am still coughing up???, or the 15 years in the glassworks breathing in all that glass dust??, no it's just the smoking "yer allright then".
if the towbar mounting points were so suseptable to wear and tear and damage and was considered critical then surely it would be part of the MOT which it is not.
colin
lutz, I think you may be over playing things a bit and making it more complicated than it needs to be, why should a third party have to take resposibility for something that you or I choose to do I guess that has more to do with the(I am not to blame so someone else must be) culture that abounds in todays world.
you said "I know of one particular case where the vehicle underbody sheet metal developed a crack after the car had been towing with two stabilisers over a significant period of time. This led to rust occuring at the crack. The car manufacturer refused to pay for the cost of the repair".
just assuming that a particular problem was caused only by one factor is to my mind flawed and without subtance, for instance how old was the car??, how long had it been used for towing??, what size trailer was it??, was the overun damper working??,what else had the car towed during it's life had it towed another car??, or pulled up tree roots ECT??, you see what I am getting at!!.
my doctor once told me that my bad chest was due to smoking!! ok I said but what about the 20 odd years I did down the pit and all the black stuff I am still coughing up???, or the 15 years in the glassworks breathing in all that glass dust??, no it's just the smoking "yer allright then".
if the towbar mounting points were so suseptable to wear and tear and damage and was considered critical then surely it would be part of the MOT which it is not.
colin
The car manufacturer is liable for all failures that occur within the specifications, i.e. so long as you remain below the max. allowable towing limits and so long as the loads imparted into the towbar do not exceed those specified in the applicable standards, including the durability requirements and ISO11555-1. Beyond that, you're on your own.
If the condition of the underbody attachment points are not included the MOT, then they should definitely be included. The underbody is probably the weakest link in the chain. The chances of cracks appearing in the adjacent sheet metal is a lot higher than a towball breaking, which is so much easier for the layman to identify in advance of it happening anyway.
If the condition of the underbody attachment points are not included the MOT, then they should definitely be included. The underbody is probably the weakest link in the chain. The chances of cracks appearing in the adjacent sheet metal is a lot higher than a towball breaking, which is so much easier for the layman to identify in advance of it happening anyway.
While I don't disagree with what you are saying Lutz I wonder if the overall actual strain on the car structure is any greater using a twin stabiliser that is sharing the loads from the caravan than it is when one stabiliser is taking the whole load
It would be interesting to see some actual data
It would be interesting to see some actual data
So long as you are below the threshold limit of when the stabiliser starts to break away, you are correct, JohnG. If the forces of instability build up to such an extent that they exceed the restraint due to friction in the stabiliser, there is no further increase in load. This is the maxmum load that the stabiliser is able to cope with and beyond which it is no longer capable of doing its job. By adding a second stabiliser, you are doubling the threshold limit and so doubling the potential load.
While I agree with both of you, that credable data and confirmation from manufacturers should be sort to define any benifit and or legallity/safety of using twin stabilisers, should the focus firstly be on loading.
After all, a properly loaded van should not sway, or require a stabiliser to be used as a pre-requisite.
The hitch incorporated stabiliser realy only seems to offer resistance to swaying (sideways movement), so I can see why you might want to fit a blade type stabiliser to assist yawing (up and down movement).
I tow a large caravan which is at the max tow limit for our car. By making sure the heavy items are as low down and over the axles as much as possible, and balancing the hitch weight to 75Kgs I get a stable tow. But I do get yawing if I don't use my snakemaster blade type stabiliser. I have replaced the shock absorbers on the car but it had little affect.
My point is that we should not run away with the idea that adding stabilisers of any type or combination, or multiple models, is a cure for a badly loaded van in the first place.
I think originally the twin stabilisers were aimed at horse boxes where nose weight is not fixed as such due to the fact that you are transporting livestock.
Steve L.
After all, a properly loaded van should not sway, or require a stabiliser to be used as a pre-requisite.
The hitch incorporated stabiliser realy only seems to offer resistance to swaying (sideways movement), so I can see why you might want to fit a blade type stabiliser to assist yawing (up and down movement).
I tow a large caravan which is at the max tow limit for our car. By making sure the heavy items are as low down and over the axles as much as possible, and balancing the hitch weight to 75Kgs I get a stable tow. But I do get yawing if I don't use my snakemaster blade type stabiliser. I have replaced the shock absorbers on the car but it had little affect.
My point is that we should not run away with the idea that adding stabilisers of any type or combination, or multiple models, is a cure for a badly loaded van in the first place.
I think originally the twin stabilisers were aimed at horse boxes where nose weight is not fixed as such due to the fact that you are transporting livestock.
Steve L.
Yes, Steve, like I said, the twin stabiliser on a horsebox is very likely to be towed by a 4x4 where I would not have quite as much concern regarding the use of two stabilisers as I would expect its underbody to be able to take the harder knocks.
However, with respect to pitching movement, the ISO standard for hitch incorporated stabilisers has the same specification regarding resistance to pitching as to yawing, so there is no reason to fit an additional blade stabiliser just in order to obtain a stiffer joint in pitching.
The safest solution, if you are concerned about the adequacy of a hitch incorporated stabiliser, is to have, in addition, a car with ESP+ and/or a caravan with an electronic stabiliser, although this only affords additional protection against swaying.
However, with respect to pitching movement, the ISO standard for hitch incorporated stabilisers has the same specification regarding resistance to pitching as to yawing, so there is no reason to fit an additional blade stabiliser just in order to obtain a stiffer joint in pitching.
The safest solution, if you are concerned about the adequacy of a hitch incorporated stabiliser, is to have, in addition, a car with ESP+ and/or a caravan with an electronic stabiliser, although this only affords additional protection against swaying.
lutz, while I accept that in theory you may have a point I do not accept that an extra 35kg of extra turning torque will cause damage and make the tow bar fall off.
the rating plate on my bar gives the values as nose weight max 75kg trailer weight max 1500kg and that is on a car with a max trailer weight of 1275kg.
my trailer mtplm is 1021kg well under both and a whopping 479kg less than the bar was designed for i just cannot see how an extra 35kg is going to make any difference to either bar,car,or trailer.
also if alko were not satisfied with the blade stabilisers and not recommended in favour of the stabiliser hitch why is the a frame pre drilled to take the blade bracket mine was.
colin
Torque is not measured in kg but Nm, so I assume you mean 35kgm (or around 350Nm). A comparison of weights with torques is meaningless.
If AlKo provide predrilled holes for blade stabilisers, then this is to satisfy those people that prefer blade stabilisers to hitch incorporated stabilisers, i.e. it's an either/or choice, not both.
That is a surprise that Alko have predrilled chassis for stabiliser brackets because I've had a few and never seen one drilled yet and have always had to use the clamp on bracket
That is not to say that yours wasn't drilled!!
I asked if Alko had a conversion kit so that the jockey wheel could be mounted on the side and they informed me that I could use their clamp but that drilling the A frame to fit it would invalidate the warranty
The Alko hitch stabiliser is far better than I imagined it could be when it first came out and I was very sceptical until I tried it
I am not aware of pitching any more than I was when using a blade type of stabiliser and I have tried a few!!
The Alko2004/3004 has 4 pads and I understood that the front/rear were to damp out pitching
That is not to say that yours wasn't drilled!!
I asked if Alko had a conversion kit so that the jockey wheel could be mounted on the side and they informed me that I could use their clamp but that drilling the A frame to fit it would invalidate the warranty
The Alko hitch stabiliser is far better than I imagined it could be when it first came out and I was very sceptical until I tried it
I am not aware of pitching any more than I was when using a blade type of stabiliser and I have tried a few!!
The Alko2004/3004 has 4 pads and I understood that the front/rear were to damp out pitching
hi lutz
just before this tread drops off the board all I can say is that after 35years of towing I know what works for me so I will not be dissuaded from using my blade stabiliser.
the upwards lift that the blade exerts on the coupling is directly opposite to that of the nose weight so cancels out some of it the alko does not assist the nose weight at all, my car with softish rear springs phyically lifts about 40 mm when the blade is engaged and gives a level plane to the unit that is better for towing. really I only use the alko because it was on the van allready and don't see any point in removing it.
they seem to work well together anyway giving a better towing ride and infinitely stable tow in any conditions, all I can say is you do it your way and I will do it mine
I am happy to leave it at that.
colin
just before this tread drops off the board all I can say is that after 35years of towing I know what works for me so I will not be dissuaded from using my blade stabiliser.
the upwards lift that the blade exerts on the coupling is directly opposite to that of the nose weight so cancels out some of it the alko does not assist the nose weight at all, my car with softish rear springs phyically lifts about 40 mm when the blade is engaged and gives a level plane to the unit that is better for towing. really I only use the alko because it was on the van allready and don't see any point in removing it.
they seem to work well together anyway giving a better towing ride and infinitely stable tow in any conditions, all I can say is you do it your way and I will do it mine
I am happy to leave it at that.
colin
A blade stabiliser does not affect the noseweight. It can only relieve the towball of some load by introducing a torque into the towbar system. The net force that the towbar transfers into the body of the towcar, however, remains the same.
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