[30ONA]

So my because I have a GV and no recovery point on the front and I have not been able to find one already designed for sale to fit 98-05 GV's I decided to start one myself. I did measurements and calcs. based on what I thought might fit on the chassis using the existing holes, with no mods and pokes through the stock bar hole. I made a cardboard template and re-checked the calcs. I've made up a prototype from MDF after doing measurements and calculations again on what would be needed with changes as required. I have a design that fits and works mathematically. I missed meeting all the scope requirements as the front bumper will need minor trimming around the hole (10-15mm).

I've come to a crossroads now. I have one design option that fits the drivers side with the stock bar (some trimming), but was designed to be used as a double recovery point, so would have a matching one on the passenger side. However to fit the design to the passenger side the stock tie down needs to be removed. The second option is to only have one recovery point on the drivers side. The problem with this is that it needs to be rated to a higher load as it is working alone.

So I want to hear peoples experiences and thoughts about how many recovery points are used on the front for recoveries. Something that is weird to me is that most recovery kits and components use an 8T snatch strap and some recovery points are rated to 8T too, but they typically use a 3.75T shackle. We all know a chain is only as strong as the weakest link. Being that the GV it not a hard core 4wd and also a lightweight vehicle, to generalise most recoveries with this vehicle will just be a simple tug to get you back on track, so I'm not working on 8T (close but not quite).

QUESTION TIME.

Do the GV and XL7 have the same chassis at the front?

If you had two recovery points on a lightweight GV would you use the two points and a bridle, or would you want to be lazy and just use one. My design can work for both however the single one will be more expensive per unit to make, but the cheaper double version will also require you to buy a bridle and second shackle.

I would also like to know if anyone has information about airbags and installations on the front of a car.

Let the discussion begin.

[Gwagensteve]

8000 is breaking strain.
3750 is WLL. For shackles breaking strain is 6X WLL.

Single point.

Your overthinking it.

Steve.

[30ONA]

Gwagensteve wrote:

8000 is breaking strain.
3750 is WLL. For shackles breaking strain is 6X WLL.

Single point.

Your overthinking it.

Steve.

As long as it is a rated shackle.

haha, it seems I forgot I already answered my own question. Just found my notes from when I checked WLL in the AS standards months ago. You are right about the WLL.

Any info re XL7 and GV chassis or air bag issues?

[30ONA]

Do the GV and XL7 have the same chassis at the front?

I would also like to know if anyone has information about airbags and installations on the front of a car.

Also who here would want to buy a ready to go bolt on recovery point for the sq GV?

[vegie]

30ONA wrote:

Also who here would want to buy a ready to go bolt on recovery point for the sq GV?

Sure. But not everyone has a standard bumper attached. I have a bullbar.

Price? Will it fit with a bullbar?

[Zook_Fan]

If you are going to be selling a recovery point you may want to consider engineering design or liability insurance.

[Gwagensteve]

Zook_Fan wrote:

If you are going to be selling a recovery point you may want to consider engineering design AND liability insurance.

[just_cruizin]

And non destructive and destructive testing

[Marck]

I looked at doing this for the NGV. By the time the product was designed tested and certified it was looking like 5-10 k having to pay for every step of development. I am sure if you where handy and had the toys to do the initial fabrication and the smarts for structural design it could be a heap less. Then on top of that the risk of someone destroying the front of an NGV doing recoveries the chassis can't cope with and trying to go after damages just made it not worth the effort and cost.

[just_cruizin]

Generally the case, however the chassis isn't really your problem. Once you do the math on the chassis shear the mount will be fine. At the end of the day you'll be attaching a 8-10mm plate to 2.5mm chassis rail which isn't great.

[30ONA]

Regarding bull bars I'd need to see how they attach but it should work for the xrox bars and standard bumper at this stage. To be honest I think it would be a lot easier to design for a car with a bull bar. But I don't have one. Happy for someone to send me picks of the mounts and images back to the cab.

Price to be determined but I would hope under $150 per unit.

Done the design for the first concept and pretty happy with it and can certify. This design at the moment suits 2T WLL based on the Gv GVM, subject to some testing, it's still early. I'm looking at testing at the moment.

Most bolt on parts are only certified for the item. Not certified for the vehicle or user once attached. A disclaimer would take care of liability issues.

Destructive testing defiantly. Can Anyone suggest somewhere. I'm calling round the likes of Bullivants at the moment. But I think I'll have more luck with a small fabricator or body shop with a chassis puller or whatever they are called.

Yes the chassis is the problem. But problems have solutions, that's why I'm posting here.

[Gwagensteve]

2T? that means it will fail before the strap. That's not what you want. You want the strap to fail before the recovery point. Do you have experience with heavy/difficult recoveries and part design?

[30ONA]

Look at your post above re WLL. 2T WLL, not 2T UL. 2T WLL is based on aGVM of 1980kg

[Gwagensteve]

Yes. I know what you wrote.

By that calculation a GV only needs a 4000lb winch.

[30ONA]

What calculation.

[Gwagensteve]

If you don't understand that the WLL for a recovery point has to exceed GVM you shouldn't be designing a recovery point.

[henno]

GVM of 1980kg.... toss that on even the slightest of inclines and you are above the 2tn WLL straight away.

20kg of headroom is not a lot of headroom for any sort of resistance. Just over 1%, in fact.

[30ONA]

So far this has been just a bashing. Lets hear some constructive criticism. Better yet how about directing me to the documents that back your comments to help me?

2T is the weight I have used as my start point for calculations as this is the legal vehicle maximum weight. The calculations made me think about using two point which was my first thought to reduce the force on one side of the chassis. I was told that I was overthinking it.

Working Load Limit (WLL), which is the maximum working load designed by the manufacturer. This load represents a force that is much less than that required to make the lifting equipment fail or yield.

Based on that definition, what I have so far is not 2T WLL, but is designed for the 1980kg GV. Lets leave WLL out of the discussion as it is only relevant when using in multiple applications and you want to know its capacity. This unit is only for one vehicle. Also as there is no specification or standard so the WLL has no definition or required value, x times stronger than something.

[Marck]

Not a bashing at all mate I would love to see you make a go of this. I have been doing a bit of researching on winches. Even for a winch they recomend that you size the winch capacity to 1.6 x GVM. Generaly a winch is not shock loaded like a recovery point can be. If you have a heavily bogged GV and somone gives it a spirited pull with something heavy say a patrol that's 4 ton on the scales. That's going to easily exert more than 2 ton. An off the shelf recovery hook is 4.5 ton WLL. If it was me that's where I would start.

[30ONA]

I'll just keep my sh1t to myself. I've gained nothing from this thread.

[henno]

30ONA wrote:

I'll just keep my sh1t to myself. I've gained nothing from this thread.

Taking your bat and ball? Facebook might be a better place for you if all you want is a circle-jerk of "Fk yeah, sick idea" type comments.

You might not be able to see it, but at least two people in this thread have tried to help you by limiting your exposure (liability wise) with regards to releasing such a product. Sure, some of the engineering specifics are thin on the ground but no one is going to spend the time outlining the entire project for you, otherwise they'd just do it themselves.

There's a few holes in your plan and a couple of people have poked fingers through them. Blame the holes, not the finger-pokers.

As a GV owner (until very recently) I personally would love to see you succeed.

[Gwagensteve]

The problem is 300NA is you've previously struggled to understand basic principles. And now you want to make the most critical and misused part ever. This stuff is hard and legally complex. But by all means take your bat and ball. Or you could be involved in the process and let us help you.

[30ONA]

Gwagensteve wrote:

The problem is 300NA is you've previously struggled to understand basic principles. And now you want to make the most critical and misused part ever. This stuff is hard and legally complex. But by all means take your bat and ball. Or you could be involved in the process and let us help you.

Ok so help. What basic principals am I getting wrong?

[jdk81]

I cbf getting into all of it, but that "disclaimer" wont mean shit.

You cant use disclaimers to avoid negligence and liability in this country.

A NATA approved testing facility would be my point if call for testing.
It wont be cheap.

Is there any welding involved in the product? Whats the design efficiency? How will you test that?

How much "math" have you done on the design?
Solidworks and FEA would be my math tools, but i know how to check the results on paper/excel.
Will you have an engineering firm review the results?

Stretched snatch straps can yank a small piece of metal to canon ball velocities, right towards one of the users. It's like russian roukette.
Trying to make a few $ as a backyarder when dealing with something so fraught with danger seems silly.

[30ONA]

The purpose of this was not to make money.

I have done the calcs from first principals. Yes fea would be a good next step. NATA testing is regulated yes, but as there is no standard here to test to NATA doesn't mean much. Any thorough logical testing is better than none. There are already units for sale that are not tested. Also there are documents stating testing is not required under certain proven design cases such as fea and a few other conditions.

If you read all the manufacturers conditions it's all about the user and fitment. I'm not trying to be dodgy. It could be designed to 10000kg but if it's not used properly then that is not the manufacturers fault.

Why is it that no one can answer a question directly? I respond to comments here and get more comments and no answers.

[just_cruizin]

Bullivants have a test centre in Brisbane, you need to test them in the same way any lifting point is done. If you use a 350 grade steel the calculated shear cross section will calculate out quite small and you'll over engineer it more just to make it look 'right' then anything else.

You are very correct in that the installer and the user bare most of the risk if you do the calcs. Depending on where the mount is fitted and the abuse it cops other than the intended use will be the 'get out'. Lifting equipment in industry gets inspected by a qualified person every 3 months and realistically even that is valid for the 2 seconds after the tag is fitted

[Zook_Fan]

Personally I'd start with AS4991 - Lifting Devices. When there are no recognised standards you should always adopt the closest best practice. However, I'd be designing for a dynamic load not static which is the case in that standard so I would include a safety factor.

You will still need a WLL limit. If you put a recovery point on a GV does that mean that the point can't be used to recover a Patrol? What about a truck? You've got to state what the recovery point is good for.

You could produce and sell a product without testing, the case to consider is when your device is involved in a fatality and a coroner is breaking down every assumption you made in the construction of your FEA and you have nothing to prove that it was correct.

I'm not sure what questions haven't been answered directly?

[jdk81]

Re the bridle question and two recovery points.

I would never use one as the equaliser straps are far too short.
They put high compressive loads into the front chassis crossmember.

[30ONA]

Thanks for the last three posts. The first two confirm my thoughts so far. I'm still trying to get the right person at bullivants. The third, I'll think about this further as I really think two points is a better combination than one in relation to applying large forces to the chassis unequally.

The current numbers give a working load capacity of 7.8t (4 times the GVM) per unit with a factor of safety of 1.5 on the chassis tearing and 2-3 on the unit itself depending on which part of the connection is looked at. I really need a test to determine the combination together and the real FOS of the unit and the unit and chassis together, FOS 2 was my minimum target. This is based on one recovery point. So you can see that one recovery point is border line, two would be great. But my concern is still chassis. I plan to get some front cuts of the chassis from a wreckers (hopefully not too rusty). I would then test the chassis and unit together before fitting to my car.

I'm really leaning towards 2 points with a bridle. GTwo points will be heavy, I might scale the plate back and see what that does. ) This also limits the pull angles and I would test accordingly. So if the current design were to work with two points, 2x 3.25t shackles, bridle and snatch strap, the capacity of the system would be limited to other parts not the unit.

[30ONA]

Actually won't scale down as I'll need to add 20% load for a dual points.