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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This does look really good. Good luck with the project.
 
Well after another marathon design evening, I've managed to figure out how to bend some RHS :ebiggrin:

I may need to do some more analysis on the spigot as I feel it is a little slender. Some stress studies will iron that one out.

For now, here is the fruits of my labours.

This a trial alignment with the arm closed:


This a trial alignment with the arm open:


Spigot and Bearing Hub
 
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Looks incredible! This is for a forester right?

Are the drawings in scale with correct dimensions or is it just in the general shape/design stage for now?

EDIT: I would recommend that the sheet metal bends/curves back up underneath, as when doing up a dune hill or rocks or any steep slope it can catch on things.
 
Yes. This is for a Forester. I've an MY05. It is all to scale and derived from measurements taken from my car and also from the Technical Manual that you can get.

You raise a good point. That is an easy alteration to the sheet metal template and I'll tackle that one later.
 
I finished the stress analysis on the draft swing arm last night and it failed. I used the weight of one of my tire and rim combinations and the cantilevered moment was to great.

I am going to toy with tilting the angle of the wheel such that it tilts back towards the window. By doing this, I change the center of gravity and bring it back more in line with the main alignment.

The other problem is trying to have two wheel carriers. Trying to get the 75 x 50 x 5 RHS to bend to the angles that I need to fit the 2 carriers in is a bit of a pain. I did however, come across some RHS product from OneSteel that has a greater Modulus of Elasticity while still maintaining the structural integrity. Problem is that it's a bit more expensive but will give the the bend flex
 
Phew... That's a massive day spent doing calcs, running design scenarios and stress elemental analysis on various configurations of the swing arms to get a combination that allows for 2 carriers, has a workable material bend scenario and does not fail stress analysis. I think I've cracked it.

Currently, as you see it, the weight comes in at 238kg (including tires and rims). That's a lot to hang off the donkey end!

I had to model tires and rims to have comparable loads for the cantilever calculations. Plus I thought it would be a little tease :discomonkey:







 
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Looks great,
Are you planning to design lighting into the bar? (stop, tail etc)
Daza.
:ebiggrin:
 
Yeah. I have to as at any point from where you stand, at least one rear light would be obstructed. Will more than likely go with a slim line LED stop/park/indicator product.
 
I've been working on the bearing pivot designs today and managed to get some more room out of them so I can increase the distance now between the 2 rear tires when they are mounted. Previously they were very close together.

I added in a design for the rear recovery hitch. The receiver is a 65 x 65 to receive a 50 x 50 towing and recovery hitch.

I also added in a mounting point for either a long range UHF antenna or it could also take the weight of a HF radio base such as the likes from CODAN.

I'll more than likely put on on the left hand arm as this I can use for mounting rear working lights.

 
That's impressive work!

I think I need to learn some new tricks ;)

Keep up the good work, I bet you can't wait to see it in the production phase!

Cheers

Bennie
 
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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