Project Rear Bar

Well, pretty much 5 years in the planning, one unit built about 4 years ago for Engineers testing and some pretty shoddy drawings saw this project parked till technology could catch up.

Now, what with plasma and laser cutters that can extrude up to 2 inch thick steel plate and software that can create all your sheets metal templates and export the design, cut and bend all to near mm precision has now seen this project reborn from the ashes.

Project Rear Bar is back on the drawing board and in CAD design phase.

Here is a sample of the partial design concept:





This is the stress analysis with results at point of material fatigue and failure. Pretty impressive stuff.


I've come up with my own rear recovery system that allows for D-shackles to be attached on either side of the rear bar. I've designed it such that they are located in the same alignment as the point of contact with the chassis. If need be, you can also have a D-shackle hitch.

For now, this is where I'm at. A massive way to go, but being able now to do the design and design analysis/testing in my own time rather than having a model built and physically testing is a major saving.

So now all I need to do is finalise the design of the sheet metal for the external panelling, design the wheel carrier arms, design the tail light locations and carrier arm couplings and then I can go into production :discomonkey:

Oh and also upgrade the wiring to the garage to take the welding kit :)
 
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I think I would rather have the tabs bend than the monoque structure and I would consider 4.5t sufficient. Let's face it, if there is something really heavy and really stuck you're not going to recover it with a Subie anyway.
 
Firstly, big thanks to Mr Turbo for getting down and dirty with the underside of his rear bar to interrogate some of the structural member sizes :discomonkey:

When doing structural design, you try to achieve a working factor of safety that is in the region of 1.5 to about 3.5. The components of the structural frame that I have designed have been coming in at 0.9 (failure) to about 1.3.

Damian has provided some indicative sizings, so it is back to the tweaking board to see the impact. I suspect that the rectangular members will have a greater capacity to withstand the constant impact of loading and unloading via the swinging of the arms and also impact of gravity and motion.

Stay tuned :monkeydance:
 
Oh crap :shrug:

The sizes that Damian provided are no longer available. Actually, and this is really odd, they have not been available for about 6 years :exclaim:

I'm just going to have to stick with my original member sizes and add some stiffeners into the design.
 
^ yes, there's nothing better than having stiffeners on your member :rotfl:
 
^^^ oh dear.

Personally I'd dump 30 - 40kg and go for a single wheel carrier, put the swing arm on a cam to get rid of the gas struts & you may also avoid the need for extra tail lights, mine passed without the need for them..................but love your skills.
 
Venom said:
I noticed on Dulagarls subaxtreme bar that the swing arms are pinched (?right word?) at the bends for extra strength...
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Actually, the "pinching" is a result of the bending. It is actually a deformation, buckling for one of a better word, of the surface. It actually reduces the integrity of the structural member but is also a function of the wall thickness albeit the overall impact is marginal and still results in a stable factor of safety when you run the numbers.

I guess it is more of a "pleasing to the eye" thing. I really don't mind the look of the buckling and I would opt for this method rather than cutting off at an angle and welding together.
 
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Just dropping in to say that things design wise are moving forwards. This past week has all be about design analysis and modification.

A few parts of the frame assembly were failing at the individual component level. The thing with design is that you have to think on 2 levels. The individual components and when they all come together. Whilst a part may fail at component level, when they all come together, it's location in the assembly plays a role and overall the whole assembly still passes.

One needs to assess where the failing part is within the assembly and how much it's failure impacts on the overall performance.

Needless to say if you over design, the impact is on weight and eventually, cost. So material sizes have been rationalised to balance weight against performance.

Here is a little materials listing that has dropped out from this weeks design review:
  • Chassis connection - 50x50x5 SHS & 12mm plate
  • Cross beam - 75 x 50 x 5 RHS
  • Hitch receiver - 65 x 65 x 6 SHS
  • Stiffening plates - 10mm
  • Swing arms - 75 x 50 x 5 RHS
  • External panel - 4mm sheet

The rear recovery points have been designed to handle 5t each but in all reality, one would do better to split the load across both rear points.

The swing arms when at full cantilever can take 300kg each. I've had to beef up the design of the bearing hub that the arms pivot on to take the load whilst also house the bearings.

In the towing department, it can take a ball weight of about 150kg and can tow about 2.5t. I did not intend for it to handle this it just happened to turn out this way. Mind you I can't see my little Foz ever towing something of that magnitude, but at least I know it can take it.

I dropped into my panel beating mate and asked him about what would be required to cut out the spare wheel well and plate it up. It is pretty straight forward, a few little cautious spots but do-able.

I've been talking to the guys at The Long Ranger. They think they can get a 40L fuel tank in there. A concept at this stage and perhaps something that I can create a provision for so down the track I can add it on.
 
Still on the case.

Been somewhat distracted what with job change and the like. Computer went potty on me so I had to ditch it and salvage the hard disk so that I could get my design data out.

Been a shocker with the Fabricator I had lined up also. His factory folded but I have now found a better crew. I was parked at the lights one morning and a Landcruiser pulled up sporting a custom rear bar. He had a sticker on the back of it for Shannon's Engineering and Design.

Went over to see them the other day and Shannon was very impressed and really keen to help out with the project. Had some really alternate ideas also what with putting various configurations of bearings in the spigot housing, also the locking mechanism for the swing arm and the one I am really keen on, incorporating a secondary fuel tank :lildevil:

So now it's back on the job and I'll keep posting as I come up with newer ideas.
 
Any progress on weight reduction? 200+ kg is veeery hefty and will cause some serious hurt on rear springs.
 
Quote:
Originally Posted by taza
Just a note don't forget the number plate has to go somewhere :)

Yup. That is going to go on the left hand side wheel :cool:
__________________
Regards,
Carlo

"Improvise, Adapt & Overcome"
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And remember that the ADR's (13/00 clause 6.8) states that it's mandatory for the rear registration plate to be illuminated, so make provision for the wiring.

Link to ADR:
https://www.comlaw.gov.au/Details/F2009C00579
 
Well I've stated procurement. I've purchased the flangeless hubs for each carrier and 3 stub axles for the 2 wheel carriers ans fuel can carrier, the rear LED working light and the LED tail light lamps.

I will post up when it all arrives. I've got the hubs and axles though.

I opted for off the shelf hubs and axles rather than having them made. The are heavy duty as I feel those I've seen are a little flimsy on the side walls.

Work has been manic and the time spent working on final designs has been little to write home about.

It's turning into a work in stages project when I get the time.
 
spinners said:
Well I've stated procurement. I've purchased the flangeless hubs for each carrier and 3 stub axles for the 2 wheel carriers ans fuel can carrier, the rear LED working light and the LED tail light lamps.

I will post up when it all arrives. I've got the hubs and axles though.

I opted for off the shelf hubs and axles rather than having them made. The are heavy duty as I feel those I've seen are a little flimsy on the side walls.

Work has been manic and the time spent working on final designs has been little to write home about.

It's turning into a work in stages project when I get the time.
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Where did you get the hubs from? I purchased mine from a bloke in Modewarre - near Geelong - and I'm extremely happy with them.

No way could they be described as flimsy!
 
Barry said:
Where did you get the hubs from? I purchased mine from a bloke in Modewarre - near Geelong - and I'm extremely happy with them.

No way could they be described as flimsy!
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I meant flimsy in the way of when you go to weld onto the hubs, if the side walls are not thick enough, you run the risk of distortion and thereby being unable to seat the outer bearing casing.

Having thicker side walls to the hubs allows the heat to disperse and reduce the chance of distortion. I guess I am one for over engineering but if I build/design something, I intend it to last a long time and withstand some punishment.
 
spinners said:
I meant flimsy in the way of when you go to weld onto the hubs, if the side walls are not thick enough, you run the risk of distortion and thereby being unable to seat the outer bearing casing.

Having thicker side walls to the hubs allows the heat to disperse and reduce the chance of distortion. I guess I am one for over engineering but if I build/design something, I intend it to last a long time and withstand some punishment.
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The ones I have are cnc turned from solid steel. Couldn't get any thicker if you wanted.
 
Does anyone know what you would call the white things and where you might be able to get them from?

dsc02317c.jpg


Any assistance would be greatly appreciated.
 
It is most likely a high density plastic like 'Pactene'. You may be able to getsome from a bearing suplly shop, or other industrial suppliers. It is very strong and wont crush under the wight it supports, it will allow the arm to slide over it like teflon, and will not wear out for ever in this application.

I used something very similar when I built my bar.


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It is the square piece under the catch pin. Sorry, this is the only pic that shows it.

Beigewagon.
 
Beigewagon said:
It is most likely a high density plastic like 'Pactene'...
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Wearex UHMWPE (Ultrahigh Molecular Weight Polyethylene)
"...A high quality plastic which offers superior impact, shock and abrasion resistance. As well, it has self-lubricating and high-slip properties and is resistant to chemical corrosion..."

:yourock:

Loads of block suppliers out there.

Thanks for your help.
 
spinners said:
dsc02317c.jpg
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Is that yours? Looks very good! Are they tow points on the back? :monkeydance:

spinners said:
Wearex UHMWPE (Ultrahigh Molecular Weight Polyethylene)
"...A high quality plastic which offers superior impact, shock and abrasion resistance. As well, it has self-lubricating and high-slip properties and is resistant to chemical corrosion..."
Click to expand...

haha that'll do the job lol :iconwink:
 
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