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Go Back   Madabout Kitcars Forum > Mad Build Area > Marlin Sportster, Cabrio, Berlinetta and Roadster builds

Marlin Sportster, Cabrio, Berlinetta and Roadster builds Enthused or Confused about your vintage Marlin build? Ask away here or show off your build.

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  #21  
Old 17th December 2007, 14:24
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I'm not sure how best they would be inspected. I think race teams X-ray their parts before use.

Given the Sportster has been on the market for 10 years and (so far) mine seems to be the only one that has had this fault I'd put it down to either weak material or a dodgy weld rather than a serious design flaw. However it does expose the weakest point of the design.

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Originally Posted by peterux View Post
Any other parts bent or damaged?

Peter
Track rod & head lamp casing. Need to take more off the car before I can say for sure.
  #22  
Old 17th December 2007, 15:13
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Gah! Bloody Hell Patrick!

Glad you're ok, and Marlin have sorted you out with replacement parts. My lower wishbones look like this:






The only thing that seemt to have changed between Patricks (and the rest of yours) and mine is that the damper mount has moved from the top of the plate to the inside of the wishbone.
  #23  
Old 17th December 2007, 15:17
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That looks substantially stronger in the area where mine broke!

Mark was also talking about the angles of the wishbones and track rods saying that steep angles are bad. He wants a picture of the front of the car with it sitting on the front so he can see what angles things are at.
  #24  
Old 17th December 2007, 15:58
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I think as Simon suggested, if the tubes were longer like the top wishbone, there wouldn't be a problem becasue the ball joint would be welded to the tubes rather than just the thin triangular plate.
Alternatively, an additional plate welded across the bottom of the ball joint socket and the lower edge of the tubes would add strength with only a little addtional weight.

Peter
  #25  
Old 17th December 2007, 16:00
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Quote:
Originally Posted by Patrick View Post
He wants a picture of the front of the car with it sitting on the front so he can see what angles things are at.
Wot? Hasn't he seen your website?
  #26  
Old 17th December 2007, 16:01
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Quote:
Originally Posted by peterux View Post
Wot? Hasn't he seen your website?
he's looked but obviously can't find what he wants to see - he watched that video I posted as well.

Quote:
Originally Posted by peterux View Post
I think as Simon suggested, if the tubes were longer like the top wishbone, there wouldn't be a problem becasue the ball joint would be welded to the tubes rather than just the thin triangular plate.
Alternatively, an additional plate welded across the bottom of the ball joint socket and the lower edge of the tubes would add strength with only a little addtional weight.

Peter

Sounds like an idea that, one of the directors at work races cars maybe he might know someone who can take a look at it for me
  #27  
Old 17th December 2007, 16:08
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Quote:
Originally Posted by Patrick View Post
:Sounds like an idea that, one of the directors at work races cars maybe he might know someone who can take a look at it for me
A professional second opinion would be a good idea at this stage.
What about the guy that welded your seat belt mounting. He looked pretty clued up.

Last edited by peterux; 17th December 2007 at 16:09.. Reason: add
  #28  
Old 17th December 2007, 16:39
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Quote:
Originally Posted by GreatOldOne View Post
The only thing that seem to have changed between Patricks (and the rest of yours) and mine is that the damper mount has moved from the top of the plate to the inside of the wishbone.
The question is why has it changed

Robin
  #29  
Old 17th December 2007, 19:18
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Quote:
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The question is why has it changed

Robin
Geometry to make the wishbones more parallel or sit the car at a different height?
  #30  
Old 17th December 2007, 22:14
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Quote:
Originally Posted by Patrick View Post
Given the Sportster has been on the market for 10 years and (so far) mine seems to be the only one that has had this fault I'd put it down to either weak material or a dodgy weld rather than a serious design flaw.
The older Ford based cars had bolt on ball joints with a subsantial mounting plate but it must be a least 5 years since the BMW version was introduced?

Your Construction photo number 34 on your website has a good shot of the wishbone when you first installed it.
  #31  
Old 18th December 2007, 07:28
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There's the comparison looks like the tubes go out further, by chance I took this photo earlier in the day (shows our extra steel weld up job on the wing carrier)



Close up 1:1

  #32  
Old 18th December 2007, 07:42
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Quote:
Originally Posted by Patrick View Post
Geometry to make the wishbones more parallel or sit the car at a different height?
Moving the spring/shoc mounting will just affect the effective spring rate - the ride height is more adjusted by the adjustable spring plate on the spring. I think there must be another reason.

Certainly it looks like the tubes extend out further on the new design.

I remember talking to someone with a blue Sportster at one of the shows (The car with the BMW instrument cluster fitted) He told me he had had a wishbone fail - albeit after thrashing it around on a track day.

Robin
  #33  
Old 18th December 2007, 08:07
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On thinking about it yeah, wouldn't change the angles of the wishbones just the ride height / adjust-ability. Maybe it lets you adjust the right high more effectively (or its purely to move the stress a bit further back on the plate?

I think I know which one you mean, that was the one with the M engine?

I've been holding back a lot while driving the Sportster for two reasons - its been damp / wet / cold and I've not done any proper set-up yet (because its cold and damp!). So its not like I've been thrashing it about.
  #34  
Old 18th December 2007, 11:15
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I've been trying to find some better pics (close ups of the end of the lower wishbone) but don't seem to have any on my webspace... I can take some tonight if you need them.

It'll give me something to do in the garage, seeing as I seem to have stalled a bit waiting for funds, only to get funds to find that Marlin have shut down for the winter early!
  #35  
Old 18th December 2007, 11:32
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Yes please
  #36  
Old 18th December 2007, 21:14
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Pics as promised:







The metal that the end plate the ball joint sits in is approx 6mm thick, and is bent at right angles at the end where the mounting point for the damper is welded on:


  #37  
Old 18th December 2007, 21:23
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That's great thank you I think Mark mentioned the metal the ball joint sits in on my design is 4mm, the bars also come further forward so it must be quite a bit stronger
  #38  
Old 18th December 2007, 21:32
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Quote:
Originally Posted by GreatOldOne View Post

The metal that the end plate the ball joint sits in is approx 6mm thick, and is bent at right angles at the end where the mounting point for the damper is welded on:

Well those pictures are really interesting, thanks.
The tubes are extended and one now goes to the centre line of the ball joint so no bending forces on that plate.
Also, my end plate is only 4mm thick! Could you check that new ones are 6mm?
So the design has certainly changed for some good reason?

Peter
  #39  
Old 18th December 2007, 21:34
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Quote:
Originally Posted by Patrick View Post
That's great thank you I think Mark mentioned the metal the ball joint sits in on my design is 4mm, the bars also come further forward so it must be quite a bit stronger
Did Mark say that the new ones are now thicker?
  #40  
Old 18th December 2007, 21:37
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Quote:
Originally Posted by MartinClan View Post
I remember talking to someone with a blue Sportster at one of the shows (The car with the BMW instrument cluster fitted) He told me he had had a wishbone fail - albeit after thrashing it around on a track day.

Robin
I think that is John from Warwick but i don't have his email address.
He frequents the MOC forum so hopefully he will see Patrick's post over there.
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