Converting from side mounting car seat to base mounting.

  1. The seats in my 450SL are getting worn and are not comfortable and to refurbish will cost more than £1200 for new leather and pads, so I decided to put them into storage for a later date and fit some TT seats I have.

    The original merc seats have rails that bolt sideways onto the inner sill and transmission tunnel, the TT seats have rails that bolt downwards into the floor.

    I am thinking about making up two angle brackets that will fit between the sill and tunnel with nuts welded beneath to bolt the TT seats on to. Each horizontal piece of bracket would need to be about 10cm wide.

    Can anyone suggest what thickness of steel to use or a better idea.

    Here are a couple of pics of the seat mounting points, two bolts and one screw each side.

    The sill to tunnel gap is 56cm and the TT rails are 40cm between centres.

    [​IMG]

    [​IMG]

    sill 581.jpg

    sill 582.jpg

    sill 599.jpg
     
  2. Pigeon_Droppings2 Member

    Messages:
    1,896
    Location:
    london
    (ignoring any MOT considerations...no idea if there would be any!) Might be better to use a U channel instead of angle...if it's quite deep I doubt it needs to be very thick steel to do the job....most cars probably would use 1.2mm or something like that if it's deep enough....wonder what the audi TT uses?

    On second thoughts could you make up a frame that bolts to the original mounting points on the merc...basically adapts your TT seat to the merc...might save a load of hassle.
     
  3. RussT

    RussT Member

    Messages:
    62
    Location:
    East Seaxe
    If the merc subframes are not removeable, see if you can find some scrap merc seat frames and adapt them to the TT base. That way you could use the original mounting points without a lot of new measuring and fabrication.
     
    8ob likes this.
  4. CompoSimmonite Member

    Messages:
    4,185
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    Werrington, Stoke-on-Trent
    Unistrut is very strong and worth looking at to make a "subframe"
     
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  5. pedrobedro

    pedrobedro Man at Matalan

    Messages:
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    You can usually find some Unistrut to adapt anything, it's like grown up's Meccano. Friend of mine has a bike trailer made of it and it's durable stuff.
     
    CompoSimmonite likes this.
  6. I was planning to use the original seat mounting holes, with two L shapes or one wide U, it needs to be strong as the seat belt anchor is on the seat frame.

    If it is two Ls then that will be a lot of bending moment as the TT seat fixing points will be 8cm from the uprights. I was thinking 5mm thick would be needed.

    sill 600.jpg
     
  7. Burdekin

    Burdekin Chief Bodger

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    Location:
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    I did this once on my P1800. What I did was make one solid crossmember that went above the floor from the inner sill to the tunnel, this was for the rear bolts. The front bolts went through the floor so what I did was weld in two boxes under the floor for these locations. I made these all from 3mm sheet.
     
    atomant48 and pdg like this.
  8. Unfortunately I cant bolt to the floor as there is a box section in the way.

    So here is my updated design, 25x25mm angle bar 5mm thick, probably an overkill but better to be safe than sorry.

    Weld the cross members to the side channels and bolt with high strength bolts.

    sill 601.jpg
     
  9. rcx132

    rcx132 Philip

    Messages:
    1,842
    Location:
    London, UK
    Construction and use regs just say it needs to be adequately strong. If you want guidance then the IVA manual sums up seat anchors in a few pages. The IVA manual is basically a simplified interpretation of construction and use regs so it's good for ensuring you're legal. You can also use the guidance in the MSA blue book which is how seats need to be mounted for race use. Both these books are designed to be understandable by the average car builder enthusiast.

    On my car I think the seat mounts use 2mm sheet metal spread plates with folded edges. These just spot weld onto the body. Surprisingly under engineered.

    Just think about twice way loads pass thru your body and design accordingly.
     
    RaceDiagnostics likes this.
  10. Burdekin

    Burdekin Chief Bodger

    Messages:
    4,588
    Location:
    Aberdeen
    Ah I see what you mean now. Yep looks good. My Amazon bolts to the floor but align with the chassis under the car.
     
  11. Burdekin

    Burdekin Chief Bodger

    Messages:
    4,588
    Location:
    Aberdeen
    Couple of pics. Has 3 bolts that attach the seat to floor and bolts into the chassis under the floor. So either above or below doing something similar is going to be fine. IMG_20171001_153756495.jpg IMG_20171001_153733582.jpg
     
    RaceDiagnostics likes this.
  12. CompoSimmonite Member

    Messages:
    4,185
    Location:
    Werrington, Stoke-on-Trent
    I find it ironic that in the early days of motoring there were no synthetic seat materials and leather was actually the "poverty" spec with cloth being for upmarket vehicles. Now it's the other way round !
    Personally, in a Merc convertible, I'd opt for MB-Tex rather than leather anyway.
     
  13. A new set of MBtex covers is almost as expensive as leather and still doesn't make them comfortable though.
     
  14. Here is the final result, it took me longer than expected to build.

    sill 680.jpg

    I needed the cut out for the seat to fully slide from the front to the back.

    sill 681.jpg

    Rear fixings.

    sill 682.jpg

    And my comfortable sitting position, I will be able to cover the visible parts of the frame with carpet.

    sill 683.jpg
     
    optima21, Cris B, Ton-up and 5 others like this.
  15. See that scabby rubber mat under the chair, I called up MB to get a price for a new one £111!

    £2.50 for some new vinyl material and some contact adhesive should do the job to tidy it up.
     
    slim_boy_fat likes this.
  16. slim_boy_fat

    slim_boy_fat Forum Supporter

    :o Aye, the 'Premium' marques know how to charge! :rolleyes: Although, oddly enough, BMW can be quite reasonable for certain bits. :)
     
  17. CompoSimmonite Member

    Messages:
    4,185
    Location:
    Werrington, Stoke-on-Trent
    Mercedes aren't too bad for Smart parts.
     
  18. jpmillermatic

    jpmillermatic Member

    Messages:
    783
    USA-NY
    very nicely done. it looks very strong too....

    JP
     
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