Hi All  Could anyone advise me, If I have  rectangle steel 65mm x 35mm x 2.5mm fixed one end 600mm long, what weight would it hold at the other end. Thanks Tom

Tom, The leverage at 600 mm is quite significant. The questions that need to be answered are how is the RHS (Rolled Hollow Section) attached at holding end ie. welded (butt or chamfered), is there a fulcrum effect at attached end ie does it lie over another piece of RHS?
Is this (lever) holding a dead weight totally perpendicular to the length of RHS, or is it the load on an angle, is there any turning moment on the RHS? Is the RHS attached to a caravan or another RHS ie on tow bar, A frame or rear bumper? Will the load be totally static or is in on a moving vehicle?
Describe the load you are desirous of placing at end of RHS. ie Spare wheel, tool box, bike rack, etc.
The origin and type of the steel used in manufacture of RHS can also effect load carrying as can the heat treating result of any welding.
A mud-map drawing of your proposal would help to get a good Engineering estimate of capacity.

Which side of RHS section is the RHS taking the load ie long side up or narrow side up?

See http://sunsetpatios.com.au/beam-deflection-calculator.php

-- Edited by Possum3 on Monday 14th of October 2019 10:22:15 AM

Steel has a specific gravity of roughly 8, so a 1 metre square sheet at 1 mm thick will weight 8kg.

So add up the perimeter of the section in metres, multiply that by the thickness in mm, multiply by the length in metres, multiply by 8.

It should be close enough for most calculations. You could calculate the radius in the corners if you need better accuracy.

Edit: I misread the question, you need an engineer to calculate the SWL.

Tom464 wrote:

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 fixed one end 600mm long, what weight would it hold at the other end. 

 

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How is it fixed?

Is it a static load or on a vehicle?

Do you have a picture?

You need to be much more specific about what you have in mind and then, maybe, some of us might give a "seat of the pants" guess.

Cheers,

Peter

I'm going to make a rear bumper bar for our caravan,  the bar will carry a little bulldog folding boat trailer 67KG.  the hollow section RHS will fit into the caravan chassis RHS which is much larger 130 x 50 x 3 and bolted,  I'm replacing the pipe bumper. I'm not welding the bumper I will have it welded, the steel I gave will be by Two with a cross member of the same size. I'm checking if one side piece holds that weight I'm happy. Thanks 

Just saw this on For Sale forum - another way to skin the cat;https://thegreynomads.activeboard.com/t65971331/boat-rack/

Thanks possum 3 you have been a very good help. Tom464

Peter_n_Margaret wrote:

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Putting 67 kg at the end of a caravan (especially at the rear) is a very bad idea from a stability perspective.
It increases the yaw inertia and WILL make the van less stable.
Cheers,
Peter

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 Absolutely right.....putting 67kg on to the rear bumper of a caravan is stupidity in the extreme,in my opinion.My car is around 15% heavier than my van,and I decided to mount a 32kg generator on the back of the van "just because". Bad move....after a one hour trip through the countryside,I decided that it was unsafe,and the generator now lives in my shed.As Peter says,the yaw inertia made the van move around  badly,even though all my axle weights, and towball weight,were good. The 67kg on your rear bumper also would take around 50kg (guess) off your towball weight.I would strongly suggest that you reconsider your decision,but I wish you only good luck. Cheers

It depends on the van as to the stability issue. I have had a van that was affected by the shift of 20kgs rearward and others totally unaffected by hanging 40 to 50 kgs off the back, but it really pays to be careful doing what you wish to do.
I have seen people hang a generator off what looks to be a fairly substaintial rear bumper bar only to lose it and the bumper bar down the road due to failure of the bumper bar supports under that load. Generator was about 30kgs.

Greg 1 wrote:

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It depends on the van as to the stability issue. I have had a van that was affected by the shift of 20kgs rearward and others totally unaffected by hanging 40 to 50 kgs off the back, but it really pays to be careful doing what you wish to do.
I have seen people hang a generator off what looks to be a fairly substaintial rear bumper bar only to lose it and the bumper bar down the road due to failure of the bumper bar supports under that load. Generator was about 30kgs.

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The problem Greg with  "and others totally unaffected by hanging 40 to 50 kgs off the back" is that usually only when the caravan and tug is out of control that the extra rearward weight is apparent.

It is similar to a car enthusiast asking if a wrong transmission oil can be used on his car and some say "I used this oil or that oil and it has worked for me for 3 years" well maybe, but that doesn't mean it will last as long as the right oil for many years after.

To be specific the caravan's tendency to yaw more easily might not be detectable until it's too late.

As most know my home built only weighs 1000kg ATM. 16ft. Recently we slowed down to 70kph as it was roo country near Rushworth and at 11pm. One huge roo appeared and I reacted with the steering and just avoided it. The van didn't sway about at all, just followed the car. It surprised me but when I think about it the 7ft of van behind the axle weighs say 400kg...not enough to have any pendulum effect. If I had 40kg off the rear bumper???

Tony

Possum3 wrote:

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Tom, Peter is correct regarding extra weight on rear of Caravan affecting stability - I personally wouldn't do it. Your other consideration must be how do you do it and keep within your plated rate. Contact Caravan Council of Australia and get an opinion from Colin Young he is an Automotive Engineer whereas I am a retired Mechanical Engineer.
Caravan Council of Australia
3 Margaret Street
Parkdale VIC 3195
T: 0409 865 399
F: 03 9587 1828

caravancouncil@optusnet.com.au

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 This argument has been going on for years.

I challenge engineers to PROVE not just make statements that for example an extra 30kg on the rear of a van with ATM and loaded to ATM of 3000kg  (say a genny in a box) is dangerous.

Please show how the dynamic stability is affected as this is only,,, 1% extra weight to the rear of the COG.

No one has ever demonstrated this to the best of my knowledge.

I worked for an engineer years ago who questioned this and he was the approving engineer for modified vehicles at MVR vehicle standards.

I hope someone takes up the challenge

See link; https://www.outbacktravelaustralia.com.au/driving-towing-towing/towball-weight-and-trailer-stability

Possum3 wrote:

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Baz, Did you note the bottom diagram and formulae on my previous post?

Note: Dimensions from the centre of the axle-group to the left are positive dimensions to the right are negative.

(Drawing would not transpose, see article for drawing if required)

Example: T = 30 kg; LC = 3.5 m; LF = 3.0 m; LR = 2.0 m
Ball-weight currently contributed by the spare wheel(s) being on the A-frame:
Ball-weight = (T x LF) / LC
= (30 X 3.0) / 3.5 = + 25.7 kg
Ball-weight decrease by the spare wheel(s) being on the rear of the van:
Ball-weight = (T x LR) / LC
= (30 X 2.0) / 3.5 = 17.1 kg
The overall effect on the ball-weight is a reduction of 48.2 kg

This formulae shows that a 30kg tyre exerts a mass of 25.7kg on ball, if mounted on rear it amounts to 48.2kg mass that will effect the Yaw potential, when transferred to rear - Although as pointed out in the article speed in major contributor to Yaw.

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 Yes got all that Possum but question was not about weight was it? Not trying to be a pain in the butt,,,, but looking for answer.... someone will know.  Cheers Baz

Hi A

Thank U I have change  the way I am thinking about the rear weight. Thank all of U Regards Tom

-- Edited by Tom464 on Monday 14th of October 2019 09:43:34 AM