I assume that for the van you would weigh each side & then the tow ball. I suppose that you could do similar with the Tug.
Tony Bev said
03:38 PM Mar 7, 2020
I purchased a similar one, a few years ago, cupie
I worked out that the ram was eight cubic centimetres, in area
Therefore for each 100 kg/cm2 of the gauge, it was lifting 800 Kg
As the gauge went up to (going from memory) 4,000 kg/cm2, I found it just too hard to read, in an accurate manner
I notice that the gauge in the link of your jack, is showing Kilograms, so it may work OK
Dougwe said
05:09 PM Mar 7, 2020
Cupie, with a topic heading like that I reckon you are playing with fire on the forum mate I hope I don't need popcorn or padlocks appear
That said and my ageing Indian mind, I see no reason why that device wouldn't give a pretty accurate reading, providing it is calibrated correctly of course. It plays two rolls as well, it is a jack and scale.
Looks the ticket.
iana said
07:26 PM Mar 7, 2020
To get an accurate reading, you would have to have three jacks, one on each side at the axle, and one under the hitch.
Cupie said
08:16 PM Mar 7, 2020
iana wrote:
To get an accurate reading, you would have to have three jacks, one on each side at the axle, and one under the hitch.
Perhaps you are right, but I wonder how much the error margin is.
My knowledge of physics is not sufficient to argue the point.
Maybe others could enlighten me.
BTW, do the weights & measures guys measure all points at the same time or do you roll your wheels on to the weigh pad in turn?
PeterInSa said
08:19 PM Mar 7, 2020
Have similar, read somewhere that mine is not that accurate for the towball weight, and agree with iana's comment above, but I have in the past weighed one side of our tandem at a time for a comparison side to side and last time I weight the van.
Cupie said
08:47 PM Mar 7, 2020
PeterInSa wrote:
Have similar, read somewhere that mine is not that accurate for the towball weight, and agree with iana's comment above, but I have in the past weighed one side of our tandem at a time for a comparison side to side and last time I weight the van.
And what was the result Peter?
Did the "side to side" weights agree with the previous ("last time I weighed the van") measurements?
PeterInSa said
02:47 AM Mar 8, 2020
Did this sometime ago, and from memory it was in the ballpark.( But that could be within 100kgs or so each side)
For a few years carried it in the boot of the van, and as I was not using it, took it out and put it in a safe place, went to use it and could not find the safe place, looked into buying another and at the time none were available. Eventually it turned up and have yet to use it again.
Don't think it is as accurate as the units you drive onto.
Radar said
07:53 AM Mar 8, 2020
One of my work positions I held a life time ago was load allocator and weighbridge clerk at a blue metal quarry. The weighbridge was of the old style with a sliding balance bar, 20 foot long (maybe shorter), 20.9 ton maximum weigh pre decimal tonne, kilograms.
Regularly a semi would weigh the prime mover and then weigh the trailer axle, add the 2 together to get a total, once a week I would need one of my weighs to turn around and approach from the other direction to do a check weigh, never in the 2 years I worked there was there a problem with the scales.
The other week I brought off the local marker a European made scales in a box never used, check weighed myself before handing over the cash, very close to my dress weight. At home, could not wait to try my bargain out, under the jockey wheel it went, guess what similar weight to my known weight.
Next morning I am in the garage, car is mostly loaded to go away except no caravan on. Weighed the right side then the left side repeated that operation again similar result to the first time. The right side of the car is 20kgs heavier then the left at the rear axle.
My next weigh project is the caravan but will need a level area for that as out driveway is on slope towards the home and lacking room to move. So that will need to wait.
The government officials on the side of the road use a 10% rule when weighing transports (I have been retired for 7 years and have not been roadside weighed checked since the 1980 ties) but I still believe there is allowed differences before taking you to court. If you are over 10%, you are over thingy.
Cupid, from my experience the officials on the side of the road with portables only weigh one axle at a time. But as I wrote earlier it's a long time for me to be weighed random on the side of the roads, even with the pads Iike at Gatton, Yamanto, Gympie since there introduction never had the experience, so I can not really say.
Jaahn said
08:07 AM Mar 8, 2020
Hi
The unit that is being discussed is a simple jack with a pressure gauge fitted that has been calibrated in KGs. That is a simple set of scales that should work in theory. My only thoughts are that the accuracy may not be very high especially at low weight like the ball weight. Having worked in a test lab for many years I can say it is hard to get good accuracy out of a simple unit like that, but if you are looking for a general indication and use it to compare from one known weight to another it could be OK.
Jaahn
Cupie said
08:07 AM Mar 8, 2020
Thanks Peter & Radar.
I am starting to form the opinion that depending on the accuracy of the scales, it is likely to be an acceptable method.
A digital display might be better to allow a more precise reading.
It would be nice to try the 3 jack approach with the one at a time reading.
Thanks all for the replies
Oops, missed the one from Jaahn. It seems to confirm my current understanding. ie. In theory the process is OK but the readings should be considered as indicative only.
-- Edited by Cupie on Sunday 8th of March 2020 09:20:57 AM
yobarr said
04:20 PM Mar 8, 2020
Jaahn wrote:
Hi
The unit that is being discussed is a simple jack with a pressure gauge fitted that has been calibrated in KGs. That is a simple set of scales that should work in theory. My only thoughts are that the accuracy may not be very high especially at low weight like the ball weight. Having worked in a test lab for many years I can say it is hard to get good accuracy out of a simple unit like that, but if you are looking for a general indication and use it to compare from one known weight to another it could be OK.
Jaahn
When I bought my van,it was being towed by an LC200 which was sitting waaaay down at the rear,so I asked about towball weight.The vendor advised that his TBW was 280kg,having "accurately" got that reading on one of those jacks.I was sceptical,and when the rear of the car rose more than 150mm when we disconnected the van,I knew something was not quite right.I bought the van anyway,because I knew that my car could handle high TBW,but subsequent testing showed a TBW of close on 400kg.Perhaps his jack was not performing as it should,but I certainly would be checking the readings provided by one of those,with those provided by the bathroom scales method,which is very accurate. After you have obtained the actual TBW,it doesn't really matter what the reading is on the jack,as long as you are careful to always load to that figure(+/-).Cheers.
Jaahn said
05:37 PM Mar 8, 2020
Hi
Assuming the pressure(KG) gauge is calibrated OK and does not get knocked about, then the major inaccuracy will be the friction in the ram and seals. Unknown quantity there but would be significant for ball weight. But if you wish to improve your accuracy I would jack it up and take a reading. Then lower it a bit, say 5mm(still off the ground), and take another reading. Then average the two readings.
Jaahn
iana said
07:39 PM Mar 8, 2020
To get any accuracy, you would have to get a level, run the opposing wheel up on a ramp, then jack the other wheel up with this unit until the bubble centralized, then raise the hitch up until that two was level. Repeat on all three axis, keeping the bubbles centralized, any altering of the centre of gravity of the van will give a false reading. Using three jacks at the same time, the weight of the van is the sum of all, no matter where the C of G is.
Cupie said
11:34 PM Mar 8, 2020
iana wrote:
To get any accuracy, you would have to get a level, run the opposing wheel up on a ramp, then jack the other wheel up with this unit until the bubble centralized, then raise the hitch up until that two was level. Repeat on all three axis, keeping the bubbles centralized, any altering of the centre of gravity of the van will give a false reading. Using three jacks at the same time, the weight of the van is the sum of all, no matter where the C of G is.
Yep. I have been thinking along the same lines.
My van is up on blocks when not in use. I was considering just jacking up each side in turn, lifting it just off the blocks thus not altering the level significantly.
BTW, they offer/recommend another jack that is claimed to be more accurate for TBW.
I recently came across this dual purpose jack & scales device that sells for what seems to be a reasonable price.
Has anyone used or seen these?
Views on their use/accuracy etc
https://www.gumtree.com.au/s-ad/dudley/caravan-campervan-accessories/tow-ball-and-caravan-weight-scale/1178834310
I assume that for the van you would weigh each side & then the tow ball. I suppose that you could do similar with the Tug.
I worked out that the ram was eight cubic centimetres, in area
Therefore for each 100 kg/cm2 of the gauge, it was lifting 800 Kg
As the gauge went up to (going from memory) 4,000 kg/cm2, I found it just too hard to read, in an accurate manner
I notice that the gauge in the link of your jack, is showing Kilograms, so it may work OK
Cupie, with a topic heading like that I reckon you are playing with fire on the forum mate
I hope I don't need popcorn or padlocks appear 
That said and my ageing Indian mind, I see no reason why that device wouldn't give a pretty accurate reading, providing it is calibrated correctly of course. It plays two rolls as well, it is a jack and scale.
Looks the ticket.
Perhaps you are right, but I wonder how much the error margin is.
My knowledge of physics is not sufficient to argue the point.
Maybe others could enlighten me.
BTW, do the weights & measures guys measure all points at the same time or do you roll your wheels on to the weigh pad in turn?
And what was the result Peter?
Did the "side to side" weights agree with the previous ("last time I weighed the van") measurements?
For a few years carried it in the boot of the van, and as I was not using it, took it out and put it in a safe place, went to use it and could not find the safe place, looked into buying another and at the time none were available. Eventually it turned up and have yet to use it again.
Don't think it is as accurate as the units you drive onto.
One of my work positions I held a life time ago was load allocator and weighbridge clerk at a blue metal quarry. The weighbridge was of the old style with a sliding balance bar, 20 foot long (maybe shorter), 20.9 ton maximum weigh pre decimal tonne, kilograms.
Regularly a semi would weigh the prime mover and then weigh the trailer axle, add the 2 together to get a total, once a week I would need one of my weighs to turn around and approach from the other direction to do a check weigh, never in the 2 years I worked there was there a problem with the scales.
The other week I brought off the local marker a European made scales in a box never used, check weighed myself before handing over the cash, very close to my dress weight. At home, could not wait to try my bargain out, under the jockey wheel it went, guess what similar weight to my known weight.
Next morning I am in the garage, car is mostly loaded to go away except no caravan on. Weighed the right side then the left side repeated that operation again similar result to the first time. The right side of the car is 20kgs heavier then the left at the rear axle.
My next weigh project is the caravan but will need a level area for that as out driveway is on slope towards the home and lacking room to move. So that will need to wait.
The government officials on the side of the road use a 10% rule when weighing transports (I have been retired for 7 years and have not been roadside weighed checked since the 1980 ties) but I still believe there is allowed differences before taking you to court. If you are over 10%, you are over thingy.
Cupid, from my experience the officials on the side of the road with portables only weigh one axle at a time. But as I wrote earlier it's a long time for me to be weighed random on the side of the roads, even with the pads Iike at Gatton, Yamanto, Gympie since there introduction never had the experience, so I can not really say.
Hi
The unit that is being discussed is a simple jack with a pressure gauge fitted that has been calibrated in KGs. That is a simple set of scales that should work in theory. My only thoughts are that the accuracy may not be very high especially at low weight like the ball weight. Having worked in a test lab for many years I can say it is hard to get good accuracy out of a simple unit like that, but if you are looking for a general indication and use it to compare from one known weight to another it could be OK.
Jaahn
Thanks Peter & Radar.
I am starting to form the opinion that depending on the accuracy of the scales, it is likely to be an acceptable method.
A digital display might be better to allow a more precise reading.
It would be nice to try the 3 jack approach with the one at a time reading.
Thanks all for the replies
Oops, missed the one from Jaahn. It seems to confirm my current understanding. ie. In theory the process is OK but the readings should be considered as indicative only.
-- Edited by Cupie on Sunday 8th of March 2020 09:20:57 AM
When I bought my van,it was being towed by an LC200 which was sitting waaaay down at the rear,so I asked about towball weight.The vendor advised that his TBW was 280kg,having "accurately" got that reading on one of those jacks.I was sceptical,and when the rear of the car rose more than 150mm when we disconnected the van,I knew something was not quite right.I bought the van anyway,because I knew that my car could handle high TBW,but subsequent testing showed a TBW of close on 400kg.Perhaps his jack was not performing as it should,but I certainly would be checking the readings provided by one of those,with those provided by the bathroom scales method,which is very accurate. After you have obtained the actual TBW,it doesn't really matter what the reading is on the jack,as long as you are careful to always load to that figure(+/-).Cheers.
Hi
Assuming the pressure(KG) gauge is calibrated OK and does not get knocked about, then the major inaccuracy will be the friction in the ram and seals. Unknown quantity there but would be significant for ball weight. But if you wish to improve your accuracy I would jack it up and take a reading. Then lower it a bit, say 5mm(still off the ground), and take another reading. Then average the two readings.
Jaahn
Yep. I have been thinking along the same lines.
My van is up on blocks when not in use. I was considering just jacking up each side in turn, lifting it just off the blocks thus not altering the level significantly.
BTW, they offer/recommend another jack that is claimed to be more accurate for TBW.
Once again, thanks all. I'm learning.