Mk2 Golf IHI track car... Rear body work and door catches

Discussion in 'Members Gallery' started by 1.8T_mk2, Dec 9, 2009.

  1. sparrow Paid Member Paid Member

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    Excellent as always.
    I've often thought about the rear roll centre, as I can sometimes feel the rear falling over, but never got around to doing anything about it.
     
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  2. vw_singh Events Team Paid Member

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    I thought the rear roll centre on a beam axle was fixed regardless of the trailing arm angle?

    I do like the wheelbase correction though. Nice.
     
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  3. FPOS New Member

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    [thread hijack, sorry!]

    I have registered on this forum for the express purpose of this thread....

    I came across this as part of the search results for dropping the front lower balljoint. I have been doing some of my own investigation on and off now for about 18 months. thank you for verifying my thinking that the spindle is cast steel and nothing to be afraid of welding to. I did the spark test with my grinder but am not able to determine anything more than that. I've finally found a VWMS catalogue from back in the day (I'm racing a mk3 btw) and I think you are on to something correct for your design of the extension.

    basically what they did was modify the production spindle as you have done, put a long bolt in there and toss a spacer in to take up the gap. from a machine design perspective, I believe this is good. I think there's a NUMBER of people on this forum who have done more recent machine design than I have but here's my logic:

    a bolt is not a good thing to use in shear, bending or to be twisted. they are to be used purely for tension. basically, what vw did was similar to regular bushings in a control arm. the bolt is under tension and the resulting pressure on the metal cylinder at the center of the busing is what keeps the arm in place. if you could get that clamping force invisibly, you wouldn't actually need a bolt there.

    so, going back to the extension. make your extension hollow, weld it to the spindle (or not), run a bolt through the whole shebang (including ball joint) and torque it down (I would have a through hole on the spindle and torque with a nut) and the whole assembly will be under compression. enough compression and any bending forces become irrelvent as the assembly may not ever end up in tension on one side. think of a beam in bending one side tension, the other in compression. if you compress the beam more than the bending moment produces tension, the result is still compression at that point. stress risers become less of an issue and you don't get those scary pics of broken extenders as shown previously in this thread.

    feel free to argue any of my points, I'm a mech engineer but have been doing non engineering work now for almost 10 years....(f*ckin Canada) so I may be off on some of the details!!!! I am hoping to get the lengths and placement of rack and extensions etc sorted over the course of the summer and get this all to work in the 15" wheels I have and do very similar to what has been done here over the winter. i'll be following this thread for sure!

    Cheers,

    FPOS (fast piece of sh*t, what my rusty Canadian mk3 is becoming!)
     
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  4. FPOS New Member

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    btw, the above post has been made without the aid of coffee yet today, please excuse the rambling contained therein!!
     
  5. vw_singh Events Team Paid Member

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  6. FPOS New Member

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    thanks very much for that thread link, glad to see that the engineering side of my brain still has a few good sparks left.

    sorry again for the highjack, looks like I have to do a lot more reading around here, you guys seem to have done it all in the past lol
     
  7. 1.8T_mk2

    1.8T_mk2 Paid Member Paid Member

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    I don't remember any effects while driving the mk2 on track but that was probably down to my lack of experience of track driving. Since driving the mk3 in anger and now I know (think I know) a little more about what's going on dynamically it's amazing what info you're able to pick-up / feel from the car.


    The angle of the trailing arm doesn't really affect the roll centre but is a by-product of moving it. The normal way to adjust the rear roll centre is to raise or lower the back of the car which moves the torsion centre and this then means the roll centre will change. As the rear is being raised or lowered the angle of the beam will inevitably change as it moves though it's arc.

    Brian G did an awesome illustration of it in this thread here...
    http://clubgti.com/showthread.php?2...m-relocators/page3&highlight=rear+roll+centre




    Hi FPOS, welcome to club gti! :thumbup:

    I appreciate you taking the time to comment :thumbup: I'm no expert in the subject by any means so it's always good to get other peoples thoughts / ideas about things as there maybe something obvious that I've missed or I could do it an easier / safer way.

    The way you describe the spacer is exactly how they are. I don't know if I got a good enough picture that shows this though. The plan is to have a nice big aerospace bolt clamping the centre of the bottom ball joint, the spacer (which will be welded to the hub) and the hub all together.

    Just been though my thread and these are the best pictures I can find of it...

    photo1-24.JPG photo1-23.JPG photo3-21.JPG photo4-21.JPG photo5-21.JPG photo2-25.JPG




    That's not the bolt I will eventually use but was the only one I could find long enough at the time.

    I never thought about the compression overriding the tension side of things but now that you've said it, it makes sense really. :thumbup:

    Where did you find that VWMS??? I thought I had a copy of one but cant seem to find it anywhere.
     
    Last edited: Dec 15, 2018
  8. 1.8T_mk2

    1.8T_mk2 Paid Member Paid Member

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    Time to brace it all up. I ordered a load of left & right handed rod ends, 4m of ews tube, some offset washers and some threaded inserts from mcgills motorsport. Once I had all the bits I could fabricate the arms for the triangulation which consisted of a length of tube with a left hand rod end one end and a right hand insert in the other.

    IMG_3774.JPG IMG_3781.JPG

    I just used tape to hold the inserts in the tube while mocking up as I wasn't a hundred percent sure on the final length.

    Next I made the centre bracket

    IMG_3871_1.JPG IMG_3870.JPG IMG_3873.JPG


    (Lost a photo here???)


    I then stopped taking photos until I got it in the car for some reason? [8(]...

    Had to notch the chassis leg a little and I won't be able to use a standard fuel tank anymore but I knew that before I started.

    Removed the stone chip / under seal from the wheel arch although I probably could have skipped this as you will find out..

    IMG_3777.JPG


    Then had to removed various parts that were fouling or no longer needed...

    IMG_3910.JPG


    Then I was time for the first test fit...
    IMG_3908.JPG IMG_3909.JPG IMG_3907.JPG IMG_3906.JPG


    So far so good. :thumbup:


    Now to get the wheels to clear the body work...
     
    Last edited: Dec 17, 2018
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  9. mk2mro New Member

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    Hello,

    Sorry to post this on your thread but I'm hoping that someone will be able to help - URGENT HELP REQUIRED for Uni Project... due in very very very too soon.

    I'm looking at structurally optimising a Mk2 Golf control arm, and as part of this require the torque at the ball joint.

    I am basing my CoG at 675mm from the floor*, and the centre of the ball joint is 175mm from the floor.

    As I saw you have mentioned earlier in this thread, T = F x D. With that in mind...my total weight of the car is 11359N and when braking, this force is trying to effectively turn around the ball joint.

    To calculate this:

    T = 11359 x (0.675 - 0.175) = 5679.2/2 = 2839.75Nm


    I am having trouble with my model when analysing the control arm using this torque figure - The stresses are massive and there is no way the part would be suitable, this is even before optimising.


    My question is, does anyone know roughly where the CoG of a Mk2 Golf is? I have based the weight distribution front/rear as 64/36 as I can reference this from a book I found.

    I understand how the CoG can be calculated but do not have time for this.

    Any help would be massively appreciated.


    *The CoG I have used of 675mm from the floor is around the main swage line in the door.

    Cheers
     
  10. 1.8T_mk2

    1.8T_mk2 Paid Member Paid Member

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    Yeah sounds like your CoG is a bit high if your using the top swage line. The highest concentrations of mass are in the subframes, engine and gear box. This normally puts the CoG around the height of the crankshaft (approximately).

    I did measure a mk2 for cog but I cant remember what I've done with the figures. I'll see if I can find them.

    How soon do you need it? When is the project due?
     
  11. FPOS New Member

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    thanks for the pics on the upright, I guess I skimmed through the thread a bit too fast to see that last bit. even though I'm in a metric country, all the easily obtainable stuff comes outta the states, so I'm going to go with a 5/8" bolt and balljoint, still PLENTY strong. I think I've also come up with a pretty simple tubular control arm idea which could make fine adjustment of camber and caster pretty simple. add that to the list of CAD that I need to do after I get the kids to bed!

    a buddy of mine here with a mk1 race car made drop plates too for his rear beam. he left the tops unsupported though (at least, no link to the centre point). I questioned that and he had a decent logic for it. under heavy loads, the flexing will produce more negative camber. granted, it's not controlled but an interesting idea. that said, the way you've built yours up will be infinitely stronger....
     
  12. FPOS New Member

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  13. mk2mro New Member

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    Hello,

    Thank you for your reply - the project is due on Monday and I need to do my optimisation work tomorrow...

    All very rushed I know (Nothing's changed in 10+ years of education haha)

    Any info would be awesome :p

    Cheers

     
  14. 1.8T_mk2

    1.8T_mk2 Paid Member Paid Member

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    Agh! You've got loads of time! :o

    Here are the figures I've got...

    Corner weights - No driver - Empty fuel tank (10ltrs max)

    Left front 314.0kg Right front 327.5kg

    Left rear 165.5kg Right rear 175.0kg

    Wheel base = 97.5" (inches)
    Track = 64" (inches)

    CoG position =

    32.7" (inches) Left to right
    33.8" (inches) Front to rear
    22.1" (inches) Vertical from the ground

    Was on 16" wheels but can't remember what the tyre size was.

    Hope this is of some use. :thumbup:

    I'd be interested to see the calculations / workings out of the load on the ball joint if that's possible. Often wondered how to calculate it but never got round to it yet. Maybe I should before I drive this thing in anger lol
     
  15. 1.8T_mk2

    1.8T_mk2 Paid Member Paid Member

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    Yeah you shouldn't have much trouble with that. I wouldn't think the spacer will be all that long either if your keeping it inside a 15" wheel which should help.
    I'd be interested to see the design I've been working on an arm design myself, I'll probably leave that for when the car is running before I start adding more jobs to the list though. lol


    I think your buddy might have it back wards with the gaining extra negative camber as the car pivots around the wheel and not the other way round.

    I always try and picture it as the car is stationary and the bottom of the wheel is getting pushed towards the car (for the outside tyre during cornering)

    rather than...

    the wheel is stationary and the car pushing against tyre.

    This would mean (if looking at the left side rear) the beam is getting rotated anticlockwise which would gain camber in the positive direction.

    I think, like I say I'm no expert lol



    Thanks for the link, been trying to find this for ages :thumbup:
     
  16. notenoughtime

    notenoughtime Moderator Moderator

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    Any updates mate :thumbup:
     
  17. 1.8T_mk2

    1.8T_mk2 Paid Member Paid Member

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    Kind of lost interest in updating the thread since the whole photobucket thing :(

    With the super slow internet connection that I have it's taken ages just to download all the photos. Wouldn't let me download all in one go so had to sit here and download one by one. It's also going to take ages to upload and update the whole thread but the good news is progress is still being made on the mk2 ! :thumbup:

    I'll make the current progress the priority and just update the rest as and when the required level of enthusiasm is reached :thumbup:
     
  18. rubjonny

    rubjonny Administrator Staff Member Admin

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    there is a short term fix, it dfoes mean editing all your posts though. add ~original to the end of each url, e.g. photobuggeredit.com/imagename.jpg~original
     
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  19. 1.8T_mk2

    1.8T_mk2 Paid Member Paid Member

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    Cheers for the info Jonny but In my blind rage I deleted the photobucket album in disgust after downloading all my pics so the links are all dead anyway. [8(]lol

    Also found a plugin for google chrome that fixes gets round it somehow with you having to do anything. Might have been patched by now though.
     
  20. rubjonny

    rubjonny Administrator Staff Member Admin

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    aye the chrome fix just does that edit for you in the browser code, but it only works for you and others who have it installed. so the links are still broken for everyone else. best fix as you say, delete your account and move elsewhere!
     
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