I am looking at carrying a bike on the rear of the van. van is 18.5 ft and at the moment no trouble with the towing, never noticed any swaying, also use a WDH. The bike weights 15kg, is this enough to cause any swaying or any other difference to the towing of the van. How much weight can you add before it will make a difference.
travelyounger said
12:31 PM Feb 6, 2021
wombat50 wrote:
I am looking at carrying a bike on the rear of the van. van is 18.5 ft and at the moment no trouble with the towing, never noticed any swaying, also use a WDH. The bike weights 15kg, is this enough to cause any swaying or any other difference to the towing of the van. How much weight can you add before it will make a difference.
Ill get in early get the popcorn and tin hat a ready
Izabarack said
12:39 PM Feb 6, 2021
Even such a small mass may be the "straw that broke the camel's back". All vans are inherently unstable and become unstable on the road at a particular speed. The critical speed is a function of the particular arrangement of the van and the current load distribution of mass across the length and breadth of the van. The length of the lever behind the axle group is the most influential component. One way to look at and consider the effect of adding 15 Kg of mass is that the critical speed at which instability occurs will be less than it is now. The only real way to determine how much effect adding 15 Kg is to just go faster, up to the posted speed limits, and see if the van gets out of shape and you crash.
Dougwe said
12:40 PM Feb 6, 2021
Maybe Cindy could move this thread to the 'weights and measures' section in Techies. That way the replies and suggestions will all be together.
wombat50 said
12:45 PM Feb 6, 2021
Hi Izabarack, if i took your advice "The only real way to determine how much effect adding 15 Kg is to just go faster, up to the posted speed limits, and see if the van gets out of shape and you crash" and did crash does this mean the 15kg was a bit to much to add.
-- Edited by wombat50 on Saturday 6th of February 2021 12:51:05 PM
Whenarewethere said
12:48 PM Feb 6, 2021
Adding weight to the ends.
Try this experiment swaying the end of the ruler around. My guess is that you may rethink where you load heavy items!
-- Edited by Whenarewethere on Saturday 6th of February 2021 12:50:23 PM
Hi Dougwe, i diddnt know that section was there and have now posted the question there. Thanks
wombat50 said
12:59 PM Feb 6, 2021
Hi Whenarewethere, i have seen the examples on you tube with toy cars towing trailers put on a conveyer belt and shifting the load. was trying to find out the approx. added weight at which can cause a change
Whenarewethere said
01:08 PM Feb 6, 2021
Anyone can test this, even using a cutting board & tins of tomatoes or bags of rice etc. If the weight is over the caravan's wheels. The tail will not be wagging the dog.
Whenarewethere said
01:15 PM Feb 6, 2021
wombat50 wrote:
Hi Whenarewethere, i have seen the examples on you tube with toy cars towing trailers put on a conveyer belt and shifting the load. was trying to find out the approx. added weight at which can cause a change
If the van is close to it's balance limit, ie it already is tending toward a rearward bias then the 15kgs could cause sway. There are so many variables here that it is very hard to say one way or another on a forum.
Really the only way to test it is to add the 15 kgs and test it out. Just edge the speed up to your normal cruise speed in small increments and feel what the van is doing. If there is no evidence of change in the way the van behaves you are fine. If it starts to feel a little twitchy you know the 15kgs has affected its stability.
This is basic test driving techniques.
bgt said
01:44 PM Feb 6, 2021
It's not just speed that is the problem. Braking, semi and wind can have an adverse affect. I've had one trailer pass me and it was still hooked to the back of the car!!!!! Now I wouldn't push my luck even with just 15kg.
Peter_n_Margaret said
01:54 PM Feb 6, 2021
Izabarack wrote:
Even such a small mass may be the "straw that broke the camel's back". All vans are inherently unstable and become unstable on the road at a particular speed. The critical speed is a function of the particular arrangement of the van and the current load distribution of mass across the length and breadth of the van. The length of the lever behind the axle group is the most influential component. One way to look at and consider the effect of adding 15 Kg of mass is that the critical speed at which instability occurs will be less than it is now. The only real way to determine how much effect adding 15 Kg is to just go faster, up to the posted speed limits, and see if the van gets out of shape and you crash.
That.
Impossible to tell if it will be a serious problem, or not, but it will be worse, and you won't be able to tell until it is too late.
Cheers,
Peter
yobarr said
02:36 PM Feb 6, 2021
wombat50 wrote:
I am looking at carrying a bike on the rear of the van. van is 18.5 ft and at the moment no trouble with the towing, never noticed any swaying, also use a WDH. The bike weights 15kg, is this enough to cause any swaying or any other difference to the towing of the van. How much weight can you add before it will make a difference.
Hi Ross...others have pointed out the variables,but I certainly would not recommend it.Is your towbal weight around 10% of your van's ATM? What is your car? I note that you have a WDH....do you understand that a WDH has NO effect on towball weight,but will take weight OFF your car's rear axle, as will putting a bike on the rear of the van.Both of these scenarios involve an increased risk of oversteer.....after his many years of working on,and driving, race cars, Greg is the resident expert in documenting dynamics of this phenomenon.Good luck with your research,but I wouldn't be doing it. My car is 16% heavier than my van,and all is well balanced,so at one stage I mounted a 30kg generator to the back of my van to see how it felt. What a nightmare! After a 50km trial run on a back road,it was removed,and is now retired in the back of my shed,never having even been started. Cheers
Aus-Kiwi said
06:14 PM Feb 6, 2021
Youll be fine . Just counterweight it with drinks, water etc up front ? Or anything forward of axles, spare tyre etc .
-- Edited by Aus-Kiwi on Saturday 6th of February 2021 06:16:55 PM
Peter_n_Margaret said
06:46 PM Feb 6, 2021
Aus-Kiwi wrote:
Youll be fine . Just counterweight it with drinks, water etc up front ? Or anything forward of axles, spare tyre etc .
It is not about balance or ball weight, it is about yaw inertia.
Cheers,
Peter
Yes, weight forward does not change the length of the lever behind the axle group.
yobarr said
07:28 PM Feb 6, 2021
I suspect that Graeme's comments were made tongue-in-cheek,as he seems to have a good understanding of weights etc.Cheers
Whenarewethere said
07:30 PM Feb 6, 2021
As said above. It has nothing to do with balance. When you balance something it is simply balanced. That it, nothing more, zilch, Nada, 0!
This is how gyroscopes function. We would all be stuffed without gyroscopes. Their mass is at the perimeter.
The further the mass is from the centre the more difficult it is to control.
Get the mass all in the centre so the tow vehicle has more control over the trailer.
I have to carry petrol outside the car, but it gets used as the tank empties. Very easy with my holder. The sand tracks & solar panels I put in the car for rough roads. The second spare wheel I can't carry it inside, but it is as central to the car as possible, including 2 x 5L of fuel in the centre of the wheel.
It is all about getting your mass as concentrated as close to the centre as possible. Lower would be better still!
Its only 15kg people !! A few suit cases inside would weigh the same ! Without a thought !! Sheesh ! Mind you if can be fitted in the front ?
oldbloke said
07:55 PM Feb 6, 2021
Unless there is other stuff mounted on the rear, say 20kg toolbox. More than likely ok. But as mentioned by others no guarantee.
Whenarewethere said
09:09 PM Feb 6, 2021
Counterbalancing is missing the point.
Izabarack said
09:10 PM Feb 6, 2021
wombat50 wrote:
"The only real way to determine how much effect adding 15 Kg is to just go faster, up to the posted speed limits, and see if the van gets out of shape and you crash" and did crash does this mean the 15kg was a bit to much to add.
Yep, that's right. One way to test the stability of a van is to steadily increase speed until it sways and gets out of control and you crash. If you do the test now, you will be able to establish the speed at which the current setup exceeds critical velocity. Always best to make decisions on changes to van configuration once you have established a baseline.
Aus-Kiwi said
09:13 PM Feb 6, 2021
Ok fit a lightweight carbon fibre bike there ! Weight and leverage yes ! Move weight to front . Wasnt meaning adding extra !!
elliemike said
09:39 PM Feb 6, 2021
wombat50 wrote:
Hi Whenarewethere, i have seen the examples on you tube with toy cars towing trailers put on a conveyer belt and shifting the load. was trying to find out the approx. added weight at which can cause a change
Where I live you see, sea kayaks & the like on roof racks. Going over bumps, at intersections, the kayaks are trying to control the car.
Ideally one should cut the kayak in thirds so it doesn't overhang.
montie said
10:34 PM Feb 6, 2021
Aus-Kiwi wrote:
Its only 15kg people !! A few suit cases inside would weigh the same ! Without a thought !! Sheesh ! Mind you if can be fitted in the front ?
Absolutely agree...15kg will have no material effect provided ball weight is around 10%.
Bobdown said
11:25 PM Feb 6, 2021
Whenarewethere wrote:
Yes.
Where I live you see, sea kayaks & the like on roof racks. Going over bumps, at intersections, the kayaks are trying to control the car.
Ideally one should cut the kayak in thirds so it doesn't overhang.
You have never towed a 3 ton van WAWT, 15 kg on the back is bugger all in the scheme of things, some have 2 x spare wheels at 60 kg+, a grey water tank could be 60 + kg.
It all depends on the van and how it is loaded etc, I have a wood rack that will take a 25 kg load, no probs at all in a 3200 kg van.
cheers Bob
Greg 1 said
01:51 AM Feb 7, 2021
That depends entirely on the van. If it is a well designed van with reasonable tow ball weight, the axle group well positioned rear of centre then 15kgs is not going to do much at all.
But you can have a van which by it's design is very susceptible to slight shifts in weight. I hired one once that was a bit of a dog to tow. After checking a few things I then shifted a bit of stuff around inside. A 20kg shift from the rear to the front and the van towed quite well.
Wanda said
09:41 AM Feb 7, 2021
Aus-Kiwi wrote:
Its only 15kg people !! A few suit cases inside would weigh the same ! Without a thought !! Sheesh ! Mind you if can be fitted in the front ?
Tend to agree, only 15kg, probably will be ok, maybe just try it, with care and mindful of what to do if something happens. Controlled enviroment!
I am looking at carrying a bike on the rear of the van. van is 18.5 ft and at the moment no trouble with the towing, never noticed any swaying, also use a WDH. The bike weights 15kg, is this enough to cause any swaying or any other difference to the towing of the van. How much weight can you add before it will make a difference.
Ill get in early get the popcorn and tin hat a ready
Hi Izabarack, if i took your advice "The only real way to determine how much effect adding 15 Kg is to just go faster, up to the posted speed limits, and see if the van gets out of shape and you crash" and did crash does this mean the 15kg was a bit to much to add.
-- Edited by wombat50 on Saturday 6th of February 2021 12:51:05 PM
Adding weight to the ends.
Try this experiment swaying the end of the ruler around. My guess is that you may rethink where you load heavy items!
-- Edited by Whenarewethere on Saturday 6th of February 2021 12:50:23 PM
Anyone can test this, even using a cutting board & tins of tomatoes or bags of rice etc. If the weight is over the caravan's wheels. The tail will not be wagging the dog.
It will be an increasing risk.
This is where we put the heavy things in our car.
That.
Impossible to tell if it will be a serious problem, or not, but it will be worse, and you won't be able to tell until it is too late.
Cheers,
Peter
Hi Ross...others have pointed out the variables,but I certainly would not recommend it.Is your towbal weight around 10% of your van's ATM? What is your car? I note that you have a WDH....do you understand that a WDH has NO effect on towball weight,but will take weight OFF your car's rear axle, as will putting a bike on the rear of the van.Both of these scenarios involve an increased risk of oversteer.....after his many years of working on,and driving, race cars, Greg is the resident expert in documenting dynamics of this phenomenon.Good luck with your research,but I wouldn't be doing it. My car is 16% heavier than my van,and all is well balanced,so at one stage I mounted a 30kg generator to the back of my van to see how it felt. What a nightmare! After a 50km trial run on a back road,it was removed,and is now retired in the back of my shed,never having even been started. Cheers
Youll be fine . Just counterweight it with drinks, water etc up front ? Or anything forward of axles, spare tyre etc .
-- Edited by Aus-Kiwi on Saturday 6th of February 2021 06:16:55 PM
It is not about balance or ball weight, it is about yaw inertia.
Cheers,
Peter
-----------------------------------------------------------------------------------------------------------------------
Yes, weight forward does not change the length of the lever behind the axle group.
I suspect that Graeme's comments were made tongue-in-cheek,as he seems to have a good understanding of weights etc.Cheers
As said above. It has nothing to do with balance. When you balance something it is simply balanced. That it, nothing more, zilch, Nada, 0!
This is how gyroscopes function. We would all be stuffed without gyroscopes. Their mass is at the perimeter.
The further the mass is from the centre the more difficult it is to control.
Get the mass all in the centre so the tow vehicle has more control over the trailer.
I have to carry petrol outside the car, but it gets used as the tank empties. Very easy with my holder. The sand tracks & solar panels I put in the car for rough roads. The second spare wheel I can't carry it inside, but it is as central to the car as possible, including 2 x 5L of fuel in the centre of the wheel.
It is all about getting your mass as concentrated as close to the centre as possible. Lower would be better still!
Counterbalancing is missing the point.
Yep, that's right. One way to test the stability of a van is to steadily increase speed until it sways and gets out of control and you crash. If you do the test now, you will be able to establish the speed at which the current setup exceeds critical velocity. Always best to make decisions on changes to van configuration once you have established a baseline.
This what you were looking for.
Yes.
Where I live you see, sea kayaks & the like on roof racks. Going over bumps, at intersections, the kayaks are trying to control the car.
Ideally one should cut the kayak in thirds so it doesn't overhang.
Absolutely agree...15kg will have no material effect provided ball weight is around 10%.
You have never towed a 3 ton van WAWT, 15 kg on the back is bugger all in the scheme of things, some have 2 x spare wheels at 60 kg+, a grey water tank could be 60 + kg.
It all depends on the van and how it is loaded etc, I have a wood rack that will take a 25 kg load, no probs at all in a 3200 kg van.
cheers Bob
Tend to agree, only 15kg, probably will be ok, maybe just try it, with care and mindful of what to do if something happens. Controlled enviroment!
regards
Ian