[douglasgiersch]

Rough design of bar im hoping to make, middle section is 150x50 and outer sections are 50x100 with hayman n reece style tow tounge. will hopefully make mounts similar to the red mounts on this page.
http://www.auszookers.com/forum/viewtopic.php?f=14&t=34438
But made to be welded to the bar.
Recovery points will be welded to a flat section of steel 50x100 on the inside section of the bar and then welded on the outside (idea with flat steel on the inside is to allow more surface area).

[oohsam]

Looks great. Nice use of sketchup.

Is that section for a towbar? I thought the towbar has mounting points already and is quite lower than that.

Cheers

[ChrisN]

My first thought: that is going to be pretty heavy.

[douglasgiersch]

Yer that section is for the towball, towbar that came with my car is shagged so figured dont replace it upgrade it.
I would imagine that it would have a good bit of wieght to it but wouldnt be anyworse than having standard towbar and a 50x100 Rhs bumper or a similar tube bar

From another view.

[oohsam]

Yes I see, Looks ok. Might need Fatzook to chime in and offer some advice on strength depending on how you plan on mounting it to the vehicle.

[Fatzook]

my only suggestion would be to build it like a Towbar with a bumber shell over it. Not the other way around.

Home made towbars can be dangerous, and aren't strictly legal either, so lets just call it a recovery point

[jdk81]

Home made towbars on sierras don't phase me as such, as the tow capacity is so low.
I saw one recently for a light truck (it was made in a factory to home made standards, and the guy took 2 weeks to make it, charging $50/hour).
It has a factor of safety of 0.3.... it is used to tow a fully loaded trailer very often.... some people don't listen, and others don't care.

ADR specs
Forwards and backwards = 1.5 x towing capacity ... 450x1.5 = 675 kg (and don't recover off it)
side-side = 0.5 x towing capacity
up and down = 0.5 x towing capacity

The step down to the hitch receiver makes it heavier and weaker than it needs to be.
You would be better off using a large drop down hitch, to achieve the tow ball height you desire.
You also shouldn't leave the rhs and/or gussets just ending on piece of flat material. You need to take it to the egde, where it can load in a non-bending manner.
This is one of the biggest mistakes fabricators make.
Adding gussets or doing a join, where it effectively makes it generate a bending load etc.


Keep it as simple as it needs to be.
Too much weight in the rear bar, will make your sierra less capable. It is easy to get carried away fabricating stuff, and your car gradually becomes less capable. Custom barwork etc looks cool, but minimalistic is where its at.


Biggest concerns
How you affix your bar to the chassis - if you use the standard holes it's fine for towing, but pretty dangerous for anything else.

As per mounting to the chassis, I advise to Balls it...
i.e. hammer some pipe through the x-member, and weld plates on the end, then bolt the rear bar to those plates.

[86slowsierra]

^^^^
This guy gets it.
You didnt say if you need the car for towing , but as they can only tow 600 kg (from memory), i honestly have no idea why sierras have a tow ball.
The factory rear bar it light, flows well and is already designed to suit the job.
just put recovery points on a stronger cross member and your good to go.

If your still keen to build this (as most people who come to a forum, ask a question then ignore all the advice, do.) consider making it a air tank as well. Look at the one P.JZook? (sp) made.

[Fatzook]

86slowsierra wrote:

but as they can only tow 600 kg (from memory),

450kg

[douglasgiersch]

[quote="86slowsierra"]If your still keen to build this (as most people who come to a forum, ask a question then ignore all the advice, do.) consider making it a air tank as well. Look at the one P.JZook? (sp) made.[/quote
AFAIK bar work for the use or airtank is a big no no in NSW atleast (where i live) and dont really like the idea of it because the amount of moisture collected from a compressor.
I dont need the towbar but in the event of a fire on the farm and it being the only vehicle around to tow a firecart i would be kicking myself very hard.
The origional towbar isnt a bad system but mine is bugger, i also have a cracked lense on tail light in bumper and fairly rusty bumper and instead of trying source 3 stock parts combineing two of the parts sounds like a fair idea, Also the stock towbar doesnt have the Hayman n Reece style tow tounge so the use of snatch blocks or pin style towing systems (used on most grain augors) is not possible.

JDK81 is this the sort of mount you were thinking, the pipe on this is slightly smaller than the bit that runs across the back of the chassis. so would i cut the excisting pipe flush, hammer that pipe all the way throught with maybe 50 or 100mm overhang each side? then weld to the pipe? and bolt to the bar.
How would you sudjest bolting it to the bar? welding of nuts on the inside of the bar sounds alright but may effect the Hi tensile strength of them wouldnt it?
I would rather bolt to chassis and weld to bar so the then the pulling force is across the bolts not up and down.
This was the mount i was planing to use.

All high tensile M8? or bigger with crush tubes on the inside or chassis.

[jdk81]

Balls winch bar mount (very rigid, but heavy).
http://auszookers.com/forum/viewtopic.php?f=14&t=7930&hilit=ball+winch+bar+mount

Passenger side will look something like this, I drilled the holes out more when I installed my rear bar.
http://auszookers.com/forum/viewtopic.php?f=14&t=8750

I slapped together a rear bar with a swing away carrier, hitch receiver I could recover off, etc a while back.
I aimed for strong enough to be safe, functional, and easy.
I have since removed the whole thing and solved the problems with a totally different method.
Car is much lighter

I used 4 bolts in each plate I welded to the car, then the two factory bolt holes per side.
I think I used a combination of m10 and m12 high tensile.

I would probably use m10 (m10 is over 50% stronger than m8).