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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Venom said:
I noticed on Dulagarls subaxtreme bar that the swing arms are pinched (?right word?) at the bends for extra strength, maybe that could be worth incorporating into your design?

Nice work so far!
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This is correct.

Spinners: this is really impressive work that you're doing. I do think you would benefit from a few pics of the detail of the bar on my vehicle. I will take some and post em, possibly this weekend. Just a few little nuances that you might not have thought of yet.
 
I've decided to go with the Hella DuraLed® 2379 Combination Lamp as it looks better and is flatter than those offered by Narva. Am still toying with the idea of slim line ones though. Not sure.

I've designed the Hella ones in and am now trying to resolve the sheet metal. The rounded corner leading to the wheel arch is proving a little tricky as you can make out from the images below.

frameassemblyrev3.jpg


frameassemblyrev4.jpg


frameassemblyrev5.jpg


I'm now trying to put to bed the open, close and over-run of the swing arms. I've seen the set-up that Kaymar have and I don't like them. I don't like the idea of a bit of metal acting as a bumper stop. I will more than likely go with a gas strut system.

Kaymar also do a nice telescopic light set-up that may just need to be sourced at the end.

I do, however, like the locking mechanism that Kaymar uses. I think that it is more durable than the system that Subaextreme have.

Alas, once I finish the sheet metal design I can start with some cardboard cut outs to test the fitting around the wheel arch.

Don't talk to me about budgets yet. It is all a function of the materials used, quantities and waste minimisation. I also need to talk to my fabricator for the materials that need to be precut.
 
I was wondering if anyone has had experience with Gas Struts? Are there any things to be cautious of or consider when selecting gas struts?
 
Give Che ("shay") at strut-regas a call 0421557440. He's very helpful. Mention me and that he supplied the stainless steel struts for the rear carriers on my Foz. (he's also doing some work on my Triton next week). He comes on site and load tests the struts and can then increase or decrease the pressure as required.
 
Well I've determined the gas struts that I'll need. Going with 8/19/250's. That is 8mm diam. rod, 19mm diam. housing and 250 stroke.

I've determined what working light I'm going to use. Narva 72715 LED Work Light with flood beam. It has 4 10W LED's. Overall 3000 Lumens. I'll just replicate the antenna base section for the telescopic tower for the working light.

I've finally sorted out the sheet metal configuration so that I minimise the waste whilst also leaving enough spare for odds and sods.

I'll start on the wheel mounting plates, number plate mount and then the swing arm locking mechanisms.

Current weight = 268kg

Here is a snap:
frameassemblywithworkin.jpg
 
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Looking awesome spinners!

We just need Barney from how I met your mother to indorse the product :p

I bet you can't wait to see it in the flesh hanging neatly from the back of your foz!! I can't wait to see pics of the real thing, how far off you reckon?

Cheers

Bennie
 
El_Freddo said:
...I can't wait to see pics of the real thing, how far off you reckon?
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I'm estimating about 8 months till I have a finished product.

I need to have my house electrical wiring redone. It's an older style house. In the process, I'll be having a dedicated uprated feed direct to the garage to handle the draw from a MIG welder. When I get some more money I can complete those works.

I also have the option of using the welding bay at my old work. I think that this will be the way to go. It's like walking into Fabricator Heaven :lildevil: The only things they don't have is a bar bender and computerised plasma cutter. Albeit the manual plasma cutter I can see come in handy.

I've got a really good contact for material supply that also has a fabrication facility that can cut my parts. I just give him an electronic file of the parts, they set it up and overnight it spits out your bits.

Depending on the costs and durations, it just might be easier to let them do all the fabrication and assembly up to a point and I'll finish off the rest.

Once I complete the 3D assembly, I'll draft the fabrication plans up and then I'll be able to get some Subbie pricing.
 
I had a good long chat to my fabricator today. He asked some pretty serious questions like had I thought about reversing sensors and a IR reversing camera since the two rear wheels will complete obscure the rear vision. Sometimes the obvious needs to be explained :lol:

I'll make provisions for the sensors to be added at a later stage by at least having the holes ready in the sheet metal. I can do something similar with the reversing camera. I was thinking of placing it under the rear working light tower or just above the towing hitch. I'd welcome peoples feedback and comments on this.
 
I ran an example render on the assembly as it stands at the moment just so I could get an idea on how well I matched up the colours.

Here is the result...
rearbarexamplefinalrend.jpg
 
I mounted my reversing camera inside the rear window under the high stop light - works well, stays clean and is within the sweep of the rear wiper (except at night 'cause the infrareds (?) reflect off the glass - I will disable them)

PS - I think you may need turn indicators in the bar as well (mine has them).
 
I'd be curious to know what people would expect as a load rating on recovery points.

Talking to some of the guys at A Noble & Son, they recommended for standard 4WD applications, 10,000lbs would be suitable. This translates into circa 4.5 tonnes, so a 4.75t rated shackle would suit.

I also remember something about sizing in that if you have a lug to attach the bow shackle to, you go one size up on the shackle. Thoughts from the Recovery Kings :poke:

Standard bow shackles for this rating have a pin diameter of 22mm and a gate opening of 32mm so I need to allow the rear recovery tab to have a 25mm diameter pin hole and tab thickness of 25mm as plate steel comes in a range from 20mm, 25mm & 32mm thick for the size shackle I may be using.

I need to design the rear recovery points to handle greater than 4.75t. The material would also need to be high tensile (AS3678-K1042). Main reason being is that it makes the shackle the weakest link.

How many tonnes would you expect a recovery point to handle?

Here are the results of the analysis that captures the assumptions above:

Deformation Plot - With a load of circa 51,000N at right angles to the tab.
What it is saying is that it would displace about 1.5mm.
recoveryassemblystudy1r.jpg


Factor of Safety Plot
The minimum FOS is 0.2. This is not good. Any FOS less than 1 means that the current design would fail. What it need to do is put in some ribs either side of the tab for lateral bracing.
recoveryassemblystudy1r.jpg
 
Hi, i followed this thread some time now and maybe i did overread it but did you mention how heavy this thing will be?

could be interesting for others too, most of you guys did get rid of the sls struts so, weight might be an issue offroading with a lot of stuff in the back and/or on the roof!
 
Yeah. It's up over 250kg at the moment. That is why I'm now spending a lot of time doing elemental analysis on the critical parts with the main objective of maintaining structural integrity and secondly to reduce weight as much as possible that does not impact on the primary.

The whole assembly, fundamentally, works as a cantilevered beam attached to the rear chassis rails. So the real key is to get the connection to the rails spot on in terms of contact integrity.

It's a rigid connection in that it is allowed to move but is a fixed point. It is a tuff one to model.
 
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