Hybrid_From_Hell Posted June 16, 2006 Share Posted June 16, 2006 K, Enclosed scrappy "back of fag-Packet Finest KittyBumper Mk2 rwear winch cradle unity thingy" I have salvaged the scrap that was the old unit, this is a 6mm shaped plate a la southdown tank guard / tow hitch styley.... I am using mainly 6mm with maybe some 8 / 10mm I am using 6mm as I think it is more than strong enough - steel is not only made stronger via thickness (which it is) but is made MUCH stronger via triangulation and gussets (Oooer Missus) As you can see from the drawing : 1. I am c**p at drawing 2. Front plate that is the upright bit will be 6mm with a 1 inch fold away from the winch, I think this will resist bending rather than a bend going back over the winch. 3. Two "side towers, prob 8mm maybe 10mm (depends - what I can "find" , with the centres machined through so that the winch centre part goes in and then the gearbox / motor goes "through" the side towers and bolt to the central part of the winch. 4. The winch will be bolted with 4 bolts through the front plate........... 5. .............and 4 bolts underneath on the base plate seam welded in between the 2 towers and over the top of the Guard itself 6. An extra center tower (shorter) seam welded between the guard and high plate 7. the 2 towers will have gussets from the towers to the front plate, 2 each side poss 10mm to traiagnulate and stop twisting on sideways pulls (what killed the last one) So, comments thoughts ideas (sensible ones please) before I hit the "production button" ? Nige Quote Link to comment Share on other sites More sharing options...
northernchris Posted June 16, 2006 Share Posted June 16, 2006 Nige I hope you do some form of stress analysis,or it will be a pile of scrap again I wouldnt know what to suggest as i havent got a clue about metal,welding,bending or anything come to think of it . Chris Quote Link to comment Share on other sites More sharing options...
northernchris Posted June 16, 2006 Share Posted June 16, 2006 Or just bring it for me to do. Chris Quote Link to comment Share on other sites More sharing options...
BogMonster Posted June 16, 2006 Share Posted June 16, 2006 Nah. Make it from 6" thick Chobham armour and be done with it. Go on you know you want to, the weight of the snorkel will stop the front wheels coming off the ground Quote Link to comment Share on other sites More sharing options...
northernchris Posted June 16, 2006 Share Posted June 16, 2006 I dont think he is playing tonight Quote Link to comment Share on other sites More sharing options...
bishbosh Posted June 16, 2006 Share Posted June 16, 2006 Nige, Being a "stress analyser" geeky type, I'll throw in my 2p: 1. I like the look of your gussetted end posts. 2. The 1" lip on the front plate is good. 3. The centre vertical plate under the winch drum is doing very little - you may want to omit it. 4. I would consider stiffening the 6mm "tray" transversally - this will bend upwards ("hog") under load. If you fitted a 2" high stiffener vetically to the back of the end posts it would do two things -firstly it will stiffen the tray as said already and secondly it will allow the concentrated tensile stresses you will get at the bottom of the end posts to be distributed laterally. 5. For belt and braces you might want some small gussets under the 1" lip to stop it un-folding as it is loaded, but I would have thought you might have other things happening before then - like a two part chassis! . The above is offered in good faith but is not based on any calculations or analysis so if it goes chesticles up again it's nuffink to do wiv me guvnor! Quote Link to comment Share on other sites More sharing options...
Jon White Posted June 16, 2006 Share Posted June 16, 2006 Yee gads who let the spider crawl over the page then???? What does some of that say??????? You wanna buy the weld in rear winch tray that scrapiron are selling....... And anyway - with that lump of metal bolted to the back end it'll DEFINATELY weigh more than Tonk's! Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted June 16, 2006 Author Share Posted June 16, 2006 Jon. Come here ........................................... Right. Yeah Tonk weighed his truck, then said he was cutting his shock mounts off n remaking in hewgh plate...so he is at it too Yee gads who let the spider crawl over the page then???? What does some of that say??????? Thats me better scrawl I'll have you know You wanna buy the weld in rear winch tray that scrapiron are selling....... Now you being rude Being now serious attention Mr Bishbosh : 4. I would consider stiffening the 6mm "tray" transversally - this will bend upwards ("hog") under load. If you fitted a 2" high stiffener vetically to the back of the end posts it would do two things -firstly it will stiffen the tray as said already and secondly it will allow the concentrated tensile stresses you will get at the bottom of the end posts to be distributed laterally. Not sure if its me being dense (behave you lot) or the booze I have imparted tonight, could you maybe explain some more unasure exactly what your saying here ? 5. For belt and braces you might want some small gussets under the 1" lip to stop it un-folding as it is loaded, but I would have thought you might have other things happening before then - like a two part chassis! Do you mean a triangle gusset with the short end under the front lip, welded then "Down" the outer edge ? Or, as in answwer 4 above Nige Quote Link to comment Share on other sites More sharing options...
landmannnn Posted June 16, 2006 Share Posted June 16, 2006 From a very simple point of view the requirement for a winch mount or tow point is transfer the forces to the chassis. Using the keep it simple principle why not make a box section similar size to the chassis mounted either side of the winch? Your plate could then go on the back as per your sketch. Much neater (and easier to draw) Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted June 16, 2006 Author Share Posted June 16, 2006 Erm Eh ? Have read it 5x have no idea Can you scribble it and post up ? Nige Quote Link to comment Share on other sites More sharing options...
northernchris Posted June 16, 2006 Share Posted June 16, 2006 Nige whats your email addy and i will ping up a couple of drawings i have done for the rear winch mount. Chris Quote Link to comment Share on other sites More sharing options...
Bush65 Posted June 17, 2006 Share Posted June 17, 2006 Nige, A lot of that steel is not going to do much as far as winching is concerned, but add weight and fabrication time. The main difficulty is that the rope tension is applied a considerable height (because the rope is winding onto the top of the drum) above the bolts where it mounts to the chassis. The winch distributes the rope load to it's end housings/feet. Then your fabricated mount has to distribute the load from the winch feet to the chassis. Considering that a 12mm dia (or there abouts) rope can withstand all of the load, your proposed mount to disperse that same load to the chassis, is inefficient. Just to digress for a moment. If you have 2 coil springs of vastly different spring rates (stiffness), the load to deflect each spring the same distance, is proportion to spring rates (stiffness). If both springs have the same free length and they are arranged with one inside the other (concentric) between platens in a press. Then both springs compess an equal amount, but most of the load will be carried by the stiffest spring. A similar thing will happen with your cradle. Most of the load will be dispersed along the stiffest route between the winch mounting feet and the bolts which mount the cradle to the chassis. Any mounting bolts, which are not in this stiffest route, will not carry much of the load (unless the highly loaded bolts fail). With your cradle, the bolts along the sides will carry nearly all of the load. The kick-up in the bottom plate, to what you call the front (your sketch) greatly reduces the membrane stiffness in the direction of the rope load. So bolts along the front flange will not carry much of the load from the winch rope. The worst case load possible from winching, will be the rope breaking force, with the rope against a drum cheek plate on the top layer. A reasonable design simplification (in your case), would be to assume rope breaking force at the top bolt for the winch mounting foot. Bearing the above in mind, concentrate first on how the forces will be distributed from this top bolt region, to where the bolts mount the cradle to the chassis. Just think about one side for now. And remember that the forces are concentrated where the cradle is stiffest between these 2 regions (where the load is applied and where it is distributed to the chassis. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted June 17, 2006 Author Share Posted June 17, 2006 John, PICCY PLEASE ? There's a lot of sensible info above, a drawing might mean I even understand it Pretty pleaase Chris You have a PM Nige Quote Link to comment Share on other sites More sharing options...
LR90 Posted June 17, 2006 Share Posted June 17, 2006 Could a MM be turned to run feet fwd rather than the stock feet down? Quote Link to comment Share on other sites More sharing options...
Bush65 Posted June 17, 2006 Share Posted June 17, 2006 Could a MM be turned to run feet fwd rather than the stock feet down? Yes they can. For some reason, I believe Nige is using his that way. Quote Link to comment Share on other sites More sharing options...
Bush65 Posted June 17, 2006 Share Posted June 17, 2006 John,PICCY PLEASE ? There's a lot of sensible info above, a drawing might mean I even understand it Pretty pleaase Chris You have a PM Nige I don't have a pic to show what I was describing. I have used fea over many years and that has made it easy for me to know how the forces are distributed (before starting to model), but it makes it hard for me to understand how others may, or may not grasp the concepts. I'm using a 10500 lb MM as a rear winch, but my rangie is chopped up at the moment (converting to tray back). The rear winch will be located onder the forward end of the tray and over to one side at an angle. The rope will run at an angle and exit through a narrow guide roller set on the centreline. The main reason for mounting the winch forward is so the rope will spool evenly onto the drum. Also the weight is better there and it is easier see. But the above will not help you. Plate is most efficient when it carries tensile loads as a membrane (ie. forces acting in the plane of the plate). The next best is planar compressive forces, then stiffening ribs or webs may be needed to prevent buckling. This depends upon the plate thickness to width ratio etc. Plate is not very good for forces that cause bending moments. I understand why you want to pull from the top of the winch. From memory, you are running the rope above the rear cross member and below the floor. Is this correct? I guess that big plate underneath is to protect the winch from mud, rocks, branches etc. My experience is with rangies. I have no experience with 90's (they are rare in Aus). Is the rear cross member strong enough for winch loads? If not, can a doubler plate be welded to the front face to strengthen it sufficiently? If yes, then an option is to bolt the winch to the front of the cross member. If you want to use the cradle, consider altering the towers. If possible, change those vertical web plates, which are parallel to the chassis rails, so they run out at an angle, from near the winch mounting feet, to the upturned flange of the bottom plate, between the chassis monting bolts. Cut their top edge down at an angle to the upturned flange. Then most of the force from the rope will be distributed along the top edge of these plates and into the upturned flange of the bottom plate near the chassis bolt. This will need some thought where the motor penetrates through one plate and the gearbox through the other. But most of the force will be in the material above the penetrations. Sorry, I had to stop part way through writing this, to watch the Wallabies thrash the 2nd string English rugby team again Quote Link to comment Share on other sites More sharing options...
bishbosh Posted June 17, 2006 Share Posted June 17, 2006 Like this: To distribute the stress well you will need lots of weld (obviously) between the stiffener and the end post for the winch. The transverse stiffener shown is addressing the same issue that Bush65 is describing (I think ) but he was being fancy using diagonal stiffs! Yes, you have interpreted the "triangle" gussets correctly, but as I said, probably OTT. Quote Link to comment Share on other sites More sharing options...
freeagent Posted June 17, 2006 Share Posted June 17, 2006 i agree with everything bish and bush 65 said, as they both appear to know loads more than me.... I know you are not interested but it would be realy interesting to run a simulation on your final design, just to see where the stress points are, and try and work out how much it deforms under a serious load... does anyone who actually knows what they're doing (which counts me out) have access to ansys or similar?? i don't mind having a crack at drawing it in ProE.... interestind to see how it turns out thats all..... Quote Link to comment Share on other sites More sharing options...
dollythelw Posted June 17, 2006 Share Posted June 17, 2006 Mine looks a bit like this - seems to work and its light 6mm winch tray, gussetted, 50x50x6 brace at the back, two recovery hooks, drop plate fixings for tow bar not sure if its any use to you Nige? ps excuse Bomb disposal Finn lurking underneath Quote Link to comment Share on other sites More sharing options...
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