LS26 Posted January 6, 2007 Share Posted January 6, 2007 Hi all, I live in a 4x4 vacuum. I have no money so have to be inventive... My latest creation on the RRC is a jackable front bumper with recovery points - well there will be two, but there's just the one for now. What I want to know is - if I was axle deep in gloop, would you be happy to give me a pull on one of these: The bumper is 100mm x 50mm x 2.7mm wall (well about that thick anyway) and the bumper support brackets are made of sections of the same. The support inboard of the chassis is about 4" long so that the bolts for the recovery point go right through this as well as through the bumper. The supports both sides of the chassis legs are seam welded everywhere they can be. I know it's a bit pigeon, but there is plenty of penetration, believe me... Here's a shot of the rear supporting bracket: So... What's the verdict - do I grind it all off and start again? Or will it be enough Rog Oh - if it makes any difference, my intention when finished is to go for the odd green lane run and monthly RTV trials. Quote Link to comment Share on other sites More sharing options...
Lewis Posted January 6, 2007 Share Posted January 6, 2007 Its not clear in the photos whether you have any washers on the boltheads, if not then you need some. Also the washers on the nuts are rather small, maybe consider larger ones or a spreader plate. Consider a spreader plate on the ring (outer) side of the bumper to spread loads from sideways pulls. Are the holes through the bumper tubed? Also ensure that both nuts and bolts are rated at least 8.8, although 10.9 or 12.9 would be preferable (from the pictures i can see they are definately not 12.9, and probably not 10.9 - 12.9 are always uncoated, and 10.9 are rarely bright coated in my experience) Lewis Quote Link to comment Share on other sites More sharing options...
Mark Posted January 6, 2007 Share Posted January 6, 2007 Rog, My concerns would be: Thickness of material - The bumper itself is not hugely thick, so on anything other than a straight forward pull is likley to start to bend. Solutions would be to tube the mounting holes, and to put a spreader plate on the front face - 6 or 8mm would be my choice. The bracket welded on is also acting as a spreader plate, but again dosn't really look think enough to me, so possibly a bit more material back there... This was on the front of my lightweeight: and whilst it was in the middle of the bunper, not up against the mounting points like yours, it had an 8mm spreader on the front a a 10mm spreader on the back. Other than that, As has been said, make sure the bolts are at least 8.8 grade (the head should have it marked on it). A lot of people would say 10.9 or 12.9 would be better, but 4 8.8 grade M12 (?) bolts should be OK. Cheers Mark Quote Link to comment Share on other sites More sharing options...
LS26 Posted January 6, 2007 Author Share Posted January 6, 2007 Thanks for the replies guys.. I was afraid that it was a bit puny - I guess it's back to the drawing board... Cheers Rog Quote Link to comment Share on other sites More sharing options...
V8RRC Posted January 6, 2007 Share Posted January 6, 2007 Just a thought you could always leave the bumper you have made just as a "bumper" & make something like these for recovery... http://www.mill-services.com/html/recovery_eyes_.html Quote Link to comment Share on other sites More sharing options...
Mark Posted January 7, 2007 Share Posted January 7, 2007 Thanks for the replies guys.. I was afraid that it was a bit puny - I guess it's back to the drawing board...Cheers Rog Not necessarily back to the drawing board, just add some strength to what you have got. It is a start, and it is certainly better than some I have seen at pay and break days... Cheers Mark Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted January 7, 2007 Share Posted January 7, 2007 I am not a guru on design, for that Mr Bish is yer man IMHO as he has helped me in the past with issues I have, I can only comment on my experience and my view of a visual, which may be right or wrong. asuuming it is right (take a huge leap of faith ) then I would comment as follows: The OD of the RHS you have is not that massive (even by my standards or is that esp by my standards) A RR stuck can weight a HUGE amount, the stickability factor is HUGE, so pulling on the centre on something this size is questionable. I also cannot rememebr reading the wall thickness, 2.7 mm is not as strong as say 4/5/6mm etc, so please advise, unless I have missed it in which case sorry.........3mm is 10 guage which is thin for this sort of thing but OD of the RHS is also crucial I would say for simple recovery "maybe" but the fixing is questionable, as these are bracketas welded to the RHS and then bolted, if the RHS was within the chassis rails and seam welded in it would be stronger... For anything approaching HD recovery "no", for this I would suggest matching the chassis drop (ie top to bottom of rail) and depth (ie front to back 75mm) and as Mark says tube it, ....then shove a gusset or 5 in like a triangle from the chassis inner side towards the centre back (or front), similar metal thickness which I would say you want a wall thickness or 4 or 5mm or even 6mm. Tubes inside the bolts in the RHS, and 8/10mm plate on back, washers and do up as tight as poss, The quality of the welds I am sorry to say is as crucial ......if not more so than the metal thickness itself I wait to be shot down, but this is my Humble Opinion.... HTH Nige Quote Link to comment Share on other sites More sharing options...
Bush65 Posted January 7, 2007 Share Posted January 7, 2007 Beefing up the attachment of the recovery eye to the bumper will not help because the mounting to the chassis is not so good. Because the bumper is raised relative to the chassis rails, the upper bolt through the chassis rail will have to take nearly all of the recovery load. The lower bolt will not share much load until the top bolt fails, then it will fail, because it then has all of the load. You have 4 bolts in tension to take the recovery load from the eye (assuming near straight pull) and 1 effective bolt in shear at the chassis. With the lack of stiffeness (due to thin material), you could not justify assuming double shear. Now bolts in shear are nowhere near as good as in tension, when there are shock loads (very low volume for strain energy). I don't like how you have made your brackets to mount to the chassis. Quote Link to comment Share on other sites More sharing options...
LS26 Posted January 7, 2007 Author Share Posted January 7, 2007 Many thanks to all for your detailed and informative replies - gosh this is a good place to come if you want to learn! I think that - from the sum of all above - I would be better saving for a few months and getting a professional job. Just a thought - what is the thinking WRT those steering guards that have built in recovery points? Maybe I could leave my effort as a bumper and fit one of those beneath? Rog Quote Link to comment Share on other sites More sharing options...
Daan Posted January 7, 2007 Share Posted January 7, 2007 not too bad in my opinion, but I would put the eye directly in line with the chassis, so get a direct pull on the chassis, rather than trying to bend the bumper.Tubing is also better, and while your at it, have threaded bushes welded in the bumper in line with the chassis, and bob is your mothers brother. daan Quote Link to comment Share on other sites More sharing options...
V8RRC Posted January 7, 2007 Share Posted January 7, 2007 Just a thought - what is the thinking WRT those steering guards that have built in recovery points? Maybe I could leave my effort as a bumper and fit one of those beneath?Rog I have one of the guards with built in recovery points (see below) & think it is spot on for the job Quote Link to comment Share on other sites More sharing options...
Simon Smith Posted January 8, 2007 Share Posted January 8, 2007 Tubes inside the bolts in the RHS, and 8/10mm plate on back, washers and do up as tight as poss, Not necessarily so. I saw the towball ripped off a motor when trying to retrieve my mates Rangy. In fact it just mised me. The bolts had been over tightened in my opinion, and were near to breaking point before the recovery even started. Apparently the new towball and bolts were recently fitted using the "as tight as possible" method. Both the new bolts failed despite the rope only being attached to the factory tie downs on my mates motor. I thought I was standing at the safe end Quote Link to comment Share on other sites More sharing options...
LS26 Posted January 8, 2007 Author Share Posted January 8, 2007 Not necessarily so. I saw the towball ripped off a motor when trying to retrieve my mates Rangy. In fact it just mised me.The bolts had been over tightened in my opinion, and were near to breaking point before the recovery even started. Apparently the new towball and bolts were recently fitted using the "as tight as possible" method. Both the new bolts failed despite the rope only being attached to the factory tie downs on my mates motor. I thought I was standing at the safe end Yes! How true... Now (to go slightly OT)... In my youth I regularly used to strip threads when tightening nuts and then at the age of 30 (MANY years ago) I finally bought a torque wrench and the revelation began... I think I am probably correct in saying that most people over-tighten most nuts most of the time. This is probably even worse when the nut (or bolt) holds something with perceived high loadings, like tow-balls or wheels for example. I myself have seen a wheel-stud break (thankfully the others held) a short time after a friend 'really gave them some welly' with just a two foot extension... So hands up: Who over-tightens their wheel-nuts? Who even knows the correct wheel-nut torque and what that torque feels like? Rog (BTW According to the RRC manual, wheel-nut torque is as follows: 125NM for alloys, 110NM for steel. And yes - I had to look it up ) Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted January 8, 2007 Share Posted January 8, 2007 Then I would say the bolts were junk ! 8.8 as a minimum and not as some muppet did a while back turn up and then argue with me that his NATO hitch on his rear crossmember was absolutely fine - and that the studding used to bolt it on with had "never let him down" Use 10.8 if you can, washers, bit of copperslip NEW Nylocs (many people don't know that a nyloc was designed as a "Once use only" locking nut. For a towball wuith say M14 / m16 8.7T or 10.8T The Hulk would have to have several weetabix to weaken them. Sadly untested shackles, and choclate cheap bolts appear all over the place, sometimes in fairmess the owner doesn't know.......sadly sometimes they do, but think they are "Ok" Nige Quote Link to comment Share on other sites More sharing options...
LS26 Posted January 8, 2007 Author Share Posted January 8, 2007 Then I would say the bolts were junk !8.8 as a minimum and not as some muppet did a while back turn up and then argue with me that his NATO hitch on his rear crossmember was absolutely fine - and that the studding used to bolt it on with had "never let him down" Use 10.8 if you can, washers, bit of copperslip NEW Nylocs (many people don't know that a nyloc was designed as a "Once use only" locking nut. For a towball wuith say M14 / m16 8.7T or 10.8T The Hulk would have to have several weetabix to weaken them. Sadly untested shackles, and choclate cheap bolts appear all over the place, sometimes in fairmess the owner doesn't know.......sadly sometimes they do, but think they are "Ok" Nige Yes - I was using 8.8 everywhere on this setup - unfortunately I thought that four-by-two box would be strong enough... Didn't think it through I guess (bit of a Muppet moment by me there). Rog Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted January 8, 2007 Share Posted January 8, 2007 Nah not a muppet moment really - you obviously "Wondered" and asked - Top marks ! What gets me going are the true mupeets, who know nothing and think they know everything, some macky chain being brought in for snatch recovery (at AWDC DRD 27th 2006) and they got the hump when I asked - then TOLD them they were not going ahead with that idea.. "We've done it for years, what makes so such an expert" type answer - the retort was mainly anglo saxon and shall we say "Firm"....they used a rope As I mentioned Natos held on with studding "Its fine mate", a towbar welded on to a std 90 bumper "My mate a proffessional welder I'll have you know" - my retort was !"well thank F he's not a chef - we would all die of food poisoning"....Recovery ropes from halfords (about 25mm), and the best was trying to use 3 ratchet strap plaited together with 2 shackles in the middle.....both untested and is one of the reasosn I have a (totally unfounded by personal) dislike and mistrust of these single bolt fixing swivelly recovery eyes that now abound everywhere ................. Muppettry is an art form and an illness, your not suffering from it as you still have a brain that asks and thinks.... <rant mode off> Can you tell this is a nerve centre of mine ? Nige Quote Link to comment Share on other sites More sharing options...
Lewis Posted January 8, 2007 Share Posted January 8, 2007 Use 10.8 if you can, washers, bit of copperslip NEW Nylocs (many people don't know that a nyloc was designed as a "Once use only" locking nut.Nige At work there has been lots of research into whether to use copperslip or not. I dont understand what the tests entailed but the result has been a complete and total ban of copperslip on threads due to an excess causing premature bolt failure, never seen it myself and i will continue to use it sparingly on my own vehicles, but the choice is yours BTW current Land Rover standard road wheel nut torque is 140NM on all models Lewis Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 8, 2007 Share Posted January 8, 2007 I'm no expert but I would not pull a bogged RR on those. The bumper itself is fine IMHO, in fact the fab is fine it's just the design details that, as you say, you don't know about because you're in a hoover For the bumper section I think your choice is OK provided you're not planning to use it as a battering ram (unlike many esp. on the challenge scene) and IMHO there's only so much steel you want to hang off the front of your vehicle. I would beef up the bits where the recovery eyes are - a thicker plate to the chassis, a bit of gusset (ooo matron!), and tube the bolt holes and if possible keep the forces in line with the chassis not above/below it. Don't give in and buy one, you're nearly there! I've even drawn a picture: The red bit is the shape I'd make the chassis-to-bumper plate, then the green bit would be a bit of thick (4-6mm) plate to beef up the area around the recovery point, the yellow bits are supposed to be gussets If you rotate the recovery points through 90 degrees can you make it so the bolt holes go either side of the chassis rail? Failing that, a normal pair of JATE rings bolted through the chassis to hang under the front of the bumper would work and leave you with a clean looking front end. Quote Link to comment Share on other sites More sharing options...
kkk2 Posted January 8, 2007 Share Posted January 8, 2007 I have always thought there was a bit of "give" in an 8.8 rated bolt where as a 10.8 or a 12.9 tend to shear straight off. I would have no problem with 8.8 on recovery equipment as long as the bolt diameter was big enough. Quote Link to comment Share on other sites More sharing options...
Les Henson Posted January 8, 2007 Share Posted January 8, 2007 Just my two-penneth. The fact that the steel is 2.7mm thick is ok - rear crossmember steel is thinner than that. The critical thing is how it is then braced/how the load is spread out, which is where spreader plates come in. I would say that the brackets that attach the bumper to the chassis rails are not up to the job - I would think they would be the first to give way. M10 with nylocs and large washers are good though, providing the bolts are 8.8 or better. The ring in the picture - aren't they designed to be used in a horizontal position, and can 'peel off' the backing plate if used vertically? Your Idea is sound, and if it was beefier, then it would be fine in my opinion. Final thing is your welding - you need to practice more. It's very poor along the bottom run, and there are bubble holes in the lower part of the side nearest the camera. Rather than pay someone else to make one, just try again, there's a lot of satisfaction in doing it yourself. I would say your first attempt is good. Les. Quote Link to comment Share on other sites More sharing options...
BogMonster Posted January 8, 2007 Share Posted January 8, 2007 a towbar welded on to a std 90 bumper "My mate a proffessional welder I'll have you know" - my retort was !"well thank F he's not a chef - we would all die of food poisoning". :hysterical: :hysterical: Can just see you saying that too Quote Link to comment Share on other sites More sharing options...
darthdicky Posted January 8, 2007 Share Posted January 8, 2007 The ring in the picture - aren't they designed to be used in a horizontal position, and can 'peel off' the backing plate if used vertically? Aren't they supposedly lifting rings for slinging it under a helicopter? If so it's probably better used as shown above! Richard Quote Link to comment Share on other sites More sharing options...
Les Henson Posted January 8, 2007 Share Posted January 8, 2007 Aren't they supposedly lifting rings for slinging it under a helicopter Yes, but aren't they in that situation mounted on top of the bumper, rather than on the front face? Les. Quote Link to comment Share on other sites More sharing options...
Andy Posted January 8, 2007 Share Posted January 8, 2007 i cant see how rotating the rings on the front of the bumper would effect the strengh. surely unless the pull is perfectly straight (never happen if you use a bridle to spread the load) then they will always be subjected to loads that could peel them off? yes i believe lifting rings are sat on top of the chassis for lifting Les. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 8, 2007 Share Posted January 8, 2007 Both wrong I'm afraid - those are pukka Stage 1 V8 recovery rings. The lifting rings are tiny little things held down with two bolts onto the top of the chassis rails, thusly: And yes, I have seen people squeeze a shackle pin through them and then try to use them for recovery! Quote Link to comment Share on other sites More sharing options...
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