| auszookers.com https://auszookers.com/forum/ |
|
| rated recovery points for a sierra https://auszookers.com/forum/viewtopic.php?f=5&t=30547 |
Page 1 of 1 |
| Author: | oldmate95 [ Fri Feb 17, 2012 3:58 pm ] |
| Post subject: | rated recovery points for a sierra |
just had a question about where to mount rated recovery hooks on my sierra i think i've got the front end sorted because i plan to bolt them through the chassis and the bullbar (one on either side so i can use a sling to spread the load) but i don't know how to go about it on the back end, wouldn't mind pics if anyone has got them. thanks in advance 
|
|
| Author: | Gwagensteve [ Fri Feb 17, 2012 5:47 pm ] |
| Post subject: | Re: rated recovery points for a sierra |
oldmate: - a solid hunk of plate (lets say 10mm thick+) with holes drilled to suit the tow bar mounting bolt holes at each side of the chassis will work a treat. Cut the plate in a "D" shape and holesaw a hole to suit your chosen shackle. This works well on WT's but doesn't work on NT's because of the narrower spring spacing. Sorry I don't think I have any photos. Have a look through the trolley tug build thread and you might catch a glimpse of the one Michael used to run on the back of the tug. *hijack on* - and apologies to you oldmate -This is in no way directed towards you - it's just that this comes up heaps and you're using the common language used to describe these things. - I'm sure a bunch of people are going to sigh and say "here he goes again".... but What is a "rated" recovery point? How does one "rate" a recovery point? I had a pintle hook on the back of Piggles. It was "rated" for 15 tonnes. Obviously, that doesn't mean I can recover a 15 tonne vehicle with piggles. Just because a hook might be "rated" with a WLL, if you bolt it to your bonnet it's not going to be rated for anything. It might also not be rated for anything if it's bolted to a sierra chassis (2.5mm) It might also not be rated for anything with an acute angle on the hook. Many years ago, I was reading the vic winch challenge rules. They stated that recovery points had to be rated for 4500kg. What a load of meaningless nonsense. Firstly, recovery is dynamic. We should be talking in Newtons, not kilograms. Secondly, it's not, in my opinion, possible to feasibly rate a connection for all possible recovery forces. It would take heaps of FEA to do. There are so many variables involved in recovery it's a minefield to try and "rate" a connection. Note I'm using the term "connection" because that's the hard bit. The hook/shackle etc is the easy bit. Connecting that to the car is the challenge. Just to muddy the waters, most people would say a shackle through the tongue of a tow bar is safe, but it's only rated for, what, 500KG on a sierra? (750Kg? - whatever) A snatch strap is rated for 9000KG WLL generally. The shackles we use to connect them to the car are generally rated at 3.25tonnes WLL. If we were to "rate" a recovery point (in Kg) what figure is acceptable? I've seen people successfully recover from 16mm eye bolts and these have a WLL of 800Kg - less than 10% of the WLL of the strap. IMHO ultimately, what each person considers a safe recovery point will really come down to the circumstances of the individual recovery. Just some thoughts to consider. I'm all for safety and well considered recovery points, I just have no idea what "rated" means. There was some interesting science done on this by Tom Sheppard many years ago and published in a book for Land Rover. He carried out strain gauge tests with various weight vehicles. I don't own the book, but do recall it was very easy to reach truly scary peak force numbers (in Newtons) on high traction surfaces. This is the link to the book http://www.amazon.com/Land-Rover-Experi ... 0854299513 Steve. |
|
| Author: | oldmate95 [ Fri Feb 17, 2012 6:35 pm ] |
| Post subject: | Re: rated recovery points for a sierra |
thanks for the advice steve, i understand what you mean about "rated" recovery hooks... i just used that terminology to avoid any confusion with people looking to flame me because they think im going to use a coat hanger or something lol, i wanted my post to be as black and white as possible so i could get the facts without the abusive safety lectures ive seen dished out on a few other 4wd forums cheers, tom |
|
| Author: | TZAR [ Fri Feb 17, 2012 6:43 pm ] |
| Post subject: | Re: rated recovery points for a sierra |
Gwagensteve wrote: A snatch strap is rated for 9000KG WLL generally. The shackles we use to connect them to the car are generally rated at 3.25tonnes WLL. If we were to "rate" a recovery point (in Kg) what figure is acceptable? I've seen people successfully recover from 16mm eye bolts and these have a WLL of 800Kg - less than 10% of the WLL of the strap. . Actually Steve it isnt a WLL (working load limit) on the strap but rather a MBS (minimum breaking strain) that they get there ratings from. And that rating is for brand new, clean, no nicks cuts drag marks covered in mud Just remember in most recoveries its best to take up the slack get it tight then accelerate. This is just pulling someone. If that doesnt work then start to slowly increase the snatch. Best to dig out the wheels FIRST remove all things that may hinder car movement BEFORE doing anything. A good pdf on a general ideas about using a strap This is like a safe work method statement (SWMS) for recoveries http://www.juststraps.com.au/pdf/Snatch ... %20pdf.pdf |
|
| Author: | JrZook [ Fri Feb 17, 2012 6:45 pm ] |
| Post subject: | Re: rated recovery points for a sierra |
^^^This guy! |
|
| Author: | oldmate95 [ Fri Feb 17, 2012 6:48 pm ] |
| Post subject: | Re: rated recovery points for a sierra |
i know ill probably sound like a fool but what does WT and NT mean? |
|
| Author: | Gwagensteve [ Fri Feb 17, 2012 7:03 pm ] |
| Post subject: | Re: rated recovery points for a sierra |
WT - wide track 1988.5 onwards NT - Narrow Track - 1982 1.0 litre through to 1988.5 1.3 Tzar - fair point about minimum breaking strain. In any case, I have no idea how you obtain a MBS in Kg - surely it should be in newtons? Steve. |
|
| Author: | oldmate95 [ Fri Feb 17, 2012 7:14 pm ] |
| Post subject: | Re: rated recovery points for a sierra |
Gwagensteve wrote: WT - wide track 1988.5 onwards NT - Narrow Track - 1982 1.0 litre through to 1988.5 1.3 . thanks 
|
|
| Author: | just_cruizin [ Fri Feb 17, 2012 8:27 pm ] |
| Post subject: | Re: rated recovery points for a sierra |
Also legally now you MUST have a damper on any and each strap used for a recovery. Therefore if you attach a strap even if you're otherwise not involved in the recovery you may be liable |
|
| Author: | Nicho03 [ Mon Aug 24, 2015 10:43 pm ] |
| Post subject: | Re: rated recovery points for a sierra |
Hi, I have read through the posts above and I am still unsure what is required as far as rated recovery points. I would like to join a club and do a few outings to learn about 4WDing but most clubs require "rated recovery points". I agree with Gwagensteve's post "What is a "rated" recovery point? How does one "rate" a recovery point?" but the 4WD clubs all seem to be asking for them. Does anyone know how to go about getting them rated? I have fitted some to my sierra which I think are more than adequate. I have seen a few Roo bars which people have fitted to their Sierras and they didn't look as securely attached as the recovery points I made. I have made mine with 12x100mm Mild steel for the recovery points and then bolted them through the frame where the two holes are at the front of the chassis rails with 10mm high tensile bolts. I have strengthened the area where the bolts go through rails with crush tubes (welded in) with 1.6mm or so wall thickness tube to provide some strength and to prevent the chassis rails collapsing in on them selves when I tightened the bolts. Also between the two recovery points I have welded a piece of 50mm square tube with 5mm wall thickness. The rear has the tow bar without the ball where I intend to put a shackle. The towbar is designed and supplied specifically for the Sierra and is rated by the manufacturer at 1000kg. |
|
| Author: | alien [ Tue Aug 25, 2015 2:34 pm ] |
| Post subject: | Re: rated recovery points for a sierra |
First ask the club how they intend to check the rating on your recovery point... if it's a visual inspection then any store-bought "rated" point should be fine to present to them. Mine's bolted to the chassis at the back but it's been heavily reinforced and gusseted - you can see it in this pic next to the left mud flap under the tail light (next to the shackle) 
|
|
| Author: | Nicho03 [ Wed Aug 26, 2015 2:19 am ] |
| Post subject: | Re: rated recovery points for a sierra |
Thanks alien. I won't pay 10 times the cost for a similar chunk of metal, therefore I won't be buying any rated recovery points...a piece of metal that's 12 mm thick is the same thing as one that is painted and called a rated recovery point. Surely it is more to do with how they're attached? I will take your advice though and see what the go is when I join a club. Cheers Nick |
|
| Page 1 of 1 | All times are UTC + 9:30 hours |
| Powered by phpBB® Forum Software © phpBB Group https://www.phpbb.com/ |
|