homemade recovery point - Page 5





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  1. #81
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    Without photos of the chassis and bumper mounts its difficult to say.

    The main criteria to look at is it should be a positive cinnection.
    Regardless of the strength.
    If the connection is crushable like this one its not a good idea.
    The moment of the main member gets deformed the connection looses most of its strength.
    In structural steel all connections are either shear or friction grip.

    Lets see some photos OwenD.

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  2. #82
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    I am going to drill some holes this weekend and mount it with just the outer bolts and take pictures of it in-situ for you on about tuesday so you can get a better idea.

    I think I might still make the plates longer than they are high as alanB has been suggesting throughout - its a sound plan, but my brain is promiscuous so I dont know what will happen between now and after the photo critiques

    I must just say now I can't thank you guys enough for helping me out!
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  3. #83
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    Before you drill, make some templates of what ever you will be bolting to the chassis. Use card board or wood. Glue them on, stand back and have a good look. For if you drill a hole, thats it.

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  4. #84

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    Quote Originally Posted by OwenD View Post

    The drop plates look like this


    1) I would weld 12 - 16mm flat bar underneath and between the two plates. Width will depend on the width of you chassis. This will then form a U to the bottom of your plate. This will stop the point wanting to swivel, and stop the bottom end squashing the chassis.

    2) I would then drill a 22mm hole (or bigger if need be) between the bottom two holes in the 16mm plate, and simply attach a shackle here.

    Keep the rest of the design as you had it, with the centre bolt and a "crushing tube" through the centre bolt.

    Leave out the shackle point, or use it on the front.
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  5. #85
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    Quote Originally Posted by Henris View Post
    All this stuff reminds me a lot of the silent p in swimming...
    Classic

  6. #86
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    Owen

    Why not get an engineering works to cut two plates, drill them as per the drop plates, but have the one longer to extend below the chassis, then have the 22mm recovery hole drilled into that area on the plate. This would eliminate the need to bolt on the recovery "thingy" you bought.

    In my mind it would take away an additional "weak" point and reduce your component count from 3 to 2 excluding the bolts & nuts.

  7. #87

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    What's really needed here is a prototype that can be tested to destruction!

    Rudolf, how would you insert the crush tube?

    Do you drill the hole through the chassis simply the size of the tube? If so how does that provide a positive joint between the chassis and the plate, surely the plate is compressed against the tube, not the chassis wall?

    Or do you weld the tube into the chassis?

  8. #88
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    Quote Originally Posted by RudolfD2 View Post
    Before you drill, make some templates of what ever you will be bolting to the chassis. Use card board or wood. Glue them on, stand back and have a good look. For if you drill a hole, thats it.
    I wont drill a hole in the chassis I meant just the mounting holes in the drop plates, so if I decide against it there is no harm done.

    Quote Originally Posted by Stockman View Post
    Why not get an engineering works to cut two plates, drill them as per the drop plates, but have the one longer to extend below the chassis, then have the 22mm recovery hole drilled into that area on the plate. This would eliminate the need to bolt on the recovery "thingy" you bought.
    This is a good idea, but I think iHilux's idea might incorporate this without me having to get extra plates made up.

    Quote Originally Posted by iHilux View Post
    2) I would then drill a 22mm hole (or bigger if need be) between the bottom two holes in the 16mm plate, and simply attach a shackle here.
    I shall take some photo's of the chassis and bumper mount this morning.

    I am interested to hear answers to alanB's questions...
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  9. #89

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    If you are going to get your own plate cut I would do something like this (attached pic).

    I only allowed a 5mm gap between the bottom of the chassis member and the 22mm hole for the shackle pin, which may not be enough to actually get the pin into the shackle, but you should get the idea.

    Also to to address Rudolfs concerns about the central bolt tearing, I'm starting to think we need two. I would place them on the centre line of the chassis, at the edges of the plate ie directly in line (vertically) with the clamping bolt holes. But those holes are now gong to carry bending moments as well so the overall force on each is going to increase! Also one has to then ask why not just rely on those two holes entirely and do away with the whole clamping thing!

    Thinking about the crush tube thing, one way could be to use different size holes through the chassis. On the side of this plate (to which the shackle will be attached) the hole would be only large enough for the bolt. On the other size it would be large enough for the tube. The tube length would have to be very precise - I would make it about .5 or perhaps even 1mm less than the outside width of the chassis member. The clamping plate on that side of the chassis would have a hole only the size of the bolt. So tightening it all up should result on both plates being clamped firmly against the chassis member AND the tube being forced against the inside of the chassis wall ensuring a positive joint for the plate below

    The tube would have to be quite substantial to exert sufficient pressure on that wall.
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    Last edited by alanB; 2009/11/14 at 09:22 AM.

  10. #90
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    I really like that design for the plate alan,

    I have taken some pictures and thought about the other suggestions some more and I am increasingly moving towards the idea of getting plates made up. luckily I have not spent any money yet except for the shackle member, I was trying all possibilities with the drop plates as they were lying around anyway - I will not be cheap when it comes to what I put on the vehicle but the viability of the free option was worth investigating.

    The problem with just milling out a 22mm hole in the existing drop plates seems to be the angle of the corners (which you have removed in your design). The straps/ropes will seemingly be damaged by the corners of the drop plates when attached to a shackle in the middle.

    The pictures show that there is actually some access to the inside of the chassis rail, but I still do not understand how this can be strengthened as ultimately any strengthening has to be bolted to the 2mm chassis which to my mind is unavoidable so load spreading is the only option. Even if you put plates on the inside they need to be attached to the chassis somewhere which leaves us at point 1?

    here is an image to stir even more debate



    perhaps I should give up not wanting to drill into the chassis and be thinking more on the lines of this, where it is bolted the length of the chassis?

    Last edited by OwenD; 2009/11/14 at 11:09 AM.
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  11. #91
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    OwenD
    The bolting arrangement of the second one looks ok but the lug itself need attantion.
    Take a tangent line from the bottom of the lug to the rear(Front) bottom corner of the mounting plate.
    Draw another nice pic and post it.
    Dont forget the doubler plate on the inside.

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  12. #92
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    Quote Originally Posted by alanB View Post
    What's really needed here is a prototype that can be tested to destruction!

    Rudolf, how would you insert the crush tube?

    Do you drill the hole through the chassis simply the size of the tube? If so how does that provide a positive joint between the chassis and the plate, surely the plate is compressed against the tube, not the chassis wall?

    Or do you weld the tube into the chassis?
    The crush tube would be inserted from open end of chassis tube and have a tight fit to the inside.
    Some motivation with mallet would be required.
    The clamping load keeps it in place. I would not weld the tube in as you mentioned although this was recommended to me.
    Welding done badly is just as dangerous as mild stel bolts in this application.

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  13. #93
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    I now want to insert a crush tube into my chassis rail as you suggested, basically a box tube slid (read hammered) into the chassis from the open end.

    Looking at a plate design somewhat like this



    the question is what thickness metal plate should I use to construct it with, and how do you attach the plates together to form a box with no protruding welds/bolts so that it is smooth enough to be hammered into place...this is becoming quite a job

    oh and rudolf I have sent a mail, it bounced back yesterday but I have tried again...
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  14. #94
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    Use counter sunk bolts or shamfer the edges , weld and grind or machine then flat. (I know that you will understand what i mean)
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  15. #95
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    I thought the idea was to use an actual tube. This would eliminate the problems of manufacture you are experiencing.

  16. #96
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    Just another idea. This is the rear recovery point on the Isuzu I posted in the beginning of the thread. I chose to bolt into the side and bottom of the chassis member since it went so far down to clear the body. For better strength the recovery point hole should have been above the pipe and I would recommend this.

    Before welding:


    Welded, painted and bolted to the chassis, although these bolts are actually too short. Note that on this vehicle the bottom of the chassis
    folds over itself and it's double thickness in that area and it's a good idea to make use of that extra strength.


    The complete rear bar. I used a thinner tube than I originally intended, and that's why it's sitting a bit too far away from the body. The tube is schedule 80 and easily supported the full weight of the vehicle at any point along the bar.


    4.75ton shackle in place.

  17. #97
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    Quote Originally Posted by Coober View Post
    I thought the idea was to use an actual tube. This would eliminate the problems of manufacture you are experiencing.
    were you thinking of something like the top picture that I have labelled bolt crush tube? Because I am planning on doing something like the bottom to basically strengthen the whole section of chassis. If you do mean the top one then while it prevents you overtightening the bolts and crushing the chassis sideways it does not really add to the strength of the bolt attachment to the chassis, whereas I think the bottom one will via clamping and friction.



    I have made this alot more long-winded than it probably had to be, and not so much reluctant to let my design go and start again but rather to try and make it work. If it seems like I am ignoring better suggestions do not think that is the case, I just want to take this particular idea to completion and then decide if I (and more importantly you guys) am/are happy with it or not. Then if it is not suitable try something else. I hope you aren't losing patience with me for seeming stubborn I am definately learning alot what to not do!

    I definately like that setup very much zantus - will probably end up doing something similar, the colt does not have a doubled up chassis on the bottom unfortunately, it slightly overlaps on the top but only by about 1.5cm which is not enough to attach anything to
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  18. #98
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    Quote Originally Posted by OwenD View Post
    were you thinking of something like the top picture that I have labelled bolt crush tube?
    Nope, as I understand it, the tube (cylinder) would be put inside the chassis in a similar manner to the 2nd picture, in place of your steel 'cuboid'.

  19. #99
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    aaah! hrmmm...will investigate that too!
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  20. #100
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    I have spoken to a salesman at 4x4 megaworld.
    He suggested that I fit a pin tow bal fitting (as per the picture below).
    He assured me that it would be strong enough as a recovery point.
    Putting the snatch strap thought the pin and locking it in place.

    Can somebody please confirm this for me before I spend the money?
    Arguments against it?

    The advantages I see is that it is in the middle of the vehicle. (eliminating using a bridle)
    Easily accessible when the vehicle is in mud.

    http://www.4x4community.co.za/forum/...1&d=1259141464
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