Results 1 to 9 of 9
  1. #1
    Join Date
    Aug 2020
    Location
    Durban
    Age
    41
    Posts
    76
    Thanked: 34

    Default Trailer Coupling Height Increase

    Greeting all

    So I have an Tow ball to trailer coupling height issue and the system fitted to my vehicle is a fixed swan neck type so no way of fitting a drop plate. Tow Ball height 510mm, Trailer coupling 465mm = 45mm Tow Ball drop. To fix I got a 50mm Solid piece of sq bar to raise to the required height, longer ht bolts and bobs your uncle. Pics Attached. Its now perfect with a slightly nose down position. Anybody see any potential issues?
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	unnamed.jpg 
Views:	171 
Size:	236.9 KB 
ID:	618285   Click image for larger version. 

Name:	IMG_3968.jpg 
Views:	166 
Size:	239.6 KB 
ID:	618286   Click image for larger version. 

Name:	IMG_3970.jpg 
Views:	161 
Size:	250.1 KB 
ID:	618287   Click image for larger version. 

Name:	IMG_3969.jpg 
Views:	159 
Size:	269.5 KB 
ID:	618288  

  2. The Following 3 Users Say Thank You to Battlestar For This Useful Post:


  3. #2
    Join Date
    Oct 2010
    Location
    Pretoria
    Age
    51
    Posts
    1,138
    Thanked: 1612

    Default Re: Trailer Coupling Height Increase

    I want to do the same for some time but havent come around to it yet. I believe my difference is much more.
    Current - 2009 Mazda BT50 3.0CRDi 4x4 d/c
    Previous - 2005 Ranger 2.5 tdi 4x2 d/c (277 422km)

  4. #3
    Join Date
    Apr 2014
    Location
    Roodepoort
    Age
    64
    Posts
    1,492
    Thanked: 5363

    Default Re: Trailer Coupling Height Increase

    I have seen some comments about the load carrying capacity of the "original" tow hooks. I know one forum member who reinforced his.

    I found out also that there are two custom made types for Jeep: Heavy duty and something like standard. These are from a proper company. My originally supplied was useless. Broke twice.

    Worth to check the max load on those tow hooks.
    Jouko
    ----------
    2003 Grand Cherokee 4.7l
    2012 Smart
    Never drive a normal car 8)

  5. #4
    Join Date
    Jun 2010
    Location
    Wilderness
    Age
    59
    Posts
    4,528
    Thanked: 1462

    Default Re: Trailer Coupling Height Increase

    Personally. I would upgrade the bolts to gr10, and not use normal gr8.8. Also i would torque those bolts to max spec, with a torque wrench. The longer bolts are more prone to stretch and bend forces. I have noted that your trailer is a 750kg without run in brake. Make sure when loading, of the correct weight distribution and tongue weight. With sudden braking, you could have a ton pushing against those bolts 2 bolts.
    Pieter Kemp.
    2011 Isuzu 300d-teq 4x4 d/c
    Home built Blapsie caravan.
    The decision you make today, will determine the road you walk tomorrow

  6. The Following User Says Thank You to Pieterk For This Useful Post:


  7. #5
    Join Date
    Jul 2011
    Location
    Brisbane
    Age
    46
    Posts
    535
    Thanked: 599

    Default Re: Trailer Coupling Height Increase

    Assuming those are M16 coarse thread bolts:
    Nom stress area is 157mm^2
    Proof Stress for G8.8 is~640MPa
    If you torque them to 75% utilisation which is what most torque tables work on
    If we use a code consistent coefficient of friction of 0.3

    2x157x640x0.75x0.3

    Those two bolts are good for circa five tons in friction grip before they see any bending or actual shear stress. So unless you routinely brake at more than six g I’d say you’re going to be 100%. If you were in Oz and asking for a “blue plate” for your mod, ie a certificate to put it on the road I’d give you one.

    The key is your using solid bar, swop that for SHS and the whole game changes.

    If you need a torque to achieve that utilisation let me know.

  8. The Following 5 Users Say Thank You to BruceB For This Useful Post:


  9. #6
    Join Date
    Aug 2020
    Location
    Durban
    Age
    41
    Posts
    76
    Thanked: 34

    Default Re: Trailer Coupling Height Increase

    Trailer is only rated GVM 500kg. Tare 320kg with 180kg payload. I recon I’m toping the scales at max 400kg. The bolts also pass through bushes in the sq tubing. They are m12

  10. #7
    Join Date
    Aug 2020
    Location
    Durban
    Age
    41
    Posts
    76
    Thanked: 34

    Default Re: Trailer Coupling Height Increase

    Quote Originally Posted by BruceB View Post
    Assuming those are M16 coarse thread bolts:
    Nom stress area is 157mm^2
    Proof Stress for G8.8 is~640MPa
    If you torque them to 75% utilisation which is what most torque tables work on
    If we use a code consistent coefficient of friction of 0.3

    2x157x640x0.75x0.3

    Those two bolts are good for circa five tons in friction grip before they see any bending or actual shear stress. So unless you routinely brake at more than six g I’d say you’re going to be 100%. If you were in Oz and asking for a “blue plate” for your mod, ie a certificate to put it on the road I’d give you one.

    The key is your using solid bar, swop that for SHS and the whole game changes.

    If you need a torque to achieve that utilisation let me know.
    would be greatful for the calcs on the m12 8,8s and a torque for tightening up.

  11. #8
    Join Date
    Aug 2020
    Location
    Durban
    Age
    41
    Posts
    76
    Thanked: 34

    Default Re: Trailer Coupling Height Increase

    Initially I was looking at using 50mm sq tube x 2.5mm thick but it didn’t look right. Found the solid sq bar and now it’s proper sturdy

  12. #9
    Join Date
    Jul 2011
    Location
    Brisbane
    Age
    46
    Posts
    535
    Thanked: 599

    Default Re: Trailer Coupling Height Increase

    Quote Originally Posted by Battlestar View Post
    would be greatful for the calcs on the m12 8,8s and a torque for tightening up.
    So an M12 has a cross sectional area of 84.3mm^2. So just replace that in the above. You need to divide by 9.81 to get it in kg, that formula gives you N.

    Working in that you get about 2.5t of friction grip. I’m not familiar with the SANS requirements for tow bars, but that’s more than enough for Oz standards, so should be Ok for SANS as well. You should torque to ~70Nm for a galv bolt lightly oiled.

  13. The Following User Says Thank You to BruceB For This Useful Post:


Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •