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 Post subject: Re: Nick's MGB Build
PostPosted: February 6, 2012, 7:54 pm 
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nick47,

You've got a lot of pro-dive (opposite of anti-dive) designed into that suspension.


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 Post subject: Re: Nick's MGB Build
PostPosted: February 7, 2012, 1:42 am 
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Well, I can't take credit for the design, but brake dive isn't a major problem on an MGB. Maintaining decent caster is more important, IMO.


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 Post subject: Re: Nick's MGB Build
PostPosted: February 7, 2012, 12:40 pm 
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nick47 wrote:
Well, I can't take credit for the design, but brake dive isn't a major problem on an MGB. Maintaining decent caster is more important, IMO.


Do you know where the suspension drawing in your earlier post was taken from, Nick? It looks like it was the output of a 3D modeling system, but could just be a good 2D illustration.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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 Post subject: Re: Nick's MGB Build
PostPosted: February 7, 2012, 7:15 pm 
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nick47 wrote:
Well, I can't take credit for the design, but brake dive isn't a major problem on an MGB. Maintaining decent caster is more important, IMO.


"Stock MGB suspensions dive quite noticeably, as do all other cars of their era", according to http://www.britishv8.org/Articles/MGB-F ... pgrade.htm

They sell caster reduction kits.


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 Post subject: Re: Nick's MGB Build
PostPosted: February 7, 2012, 7:46 pm 
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I owned and raced several MGBs over the years, and dive wasn't a major problem, at least for me. It was a major problem on my grandma's old Buick, however. On the MGBs I always ran stock caster, 7 degrees, but on the Locost I'm going with 5.


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 Post subject: Re: Nick's MGB Build
PostPosted: February 7, 2012, 8:19 pm 
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I'm "inclined" to agree with Nick.

I think everybody with parallel arms perpendicular to the ground has some anti-dive, and Nick will have less than those guys, with less of the negative affects a lightweight car would be sensitive to.

On miatas, the spec is around 4-1/2 with most folks looking for more, with the uca pivots angled upward at the front but with a horizontal lca for converging axes.

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 Post subject: Re: Nick's MGB Build
PostPosted: February 15, 2012, 2:19 pm 
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nick47 wrote:
Yeah, I had to work that out. I think it's just a matter of moving the pickups around, and making sure the bracket holes are still parallel and all in the same plane. I worked out the angles and the LB and FU tubes don't change very much if I set caster at 5 dgrees.

BTW, all the other MGB Locosts I've seen (a total of 2) ran with zero caster. So I'm hoping this will be better.

Image



Hey nick. Do you have a top down view of your front suspension as detailed as the side? Your basic dimensions are helping me immeasurably!

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 Post subject: Re: Nick's MGB Build
PostPosted: February 15, 2012, 5:36 pm 
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Not sure it's as detailed, but here's what I've got.

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 Post subject: Re: Nick's MGB Build
PostPosted: February 15, 2012, 9:19 pm 
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Hey Nick
How did you arrive at the A arm lengths and mounting points on the chassis? Were these taken directly off a B? If you don't mind I am inclined to use your numbers for my Sprite into Locost build.
Tim


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 Post subject: Re: Nick's MGB Build
PostPosted: February 16, 2012, 12:36 am 
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You don't have a lot of suspension design options when you start with MGB swivel axles and a book frame. A-arm lengths were determined by the width of the chassis, width of the track (52", to match the rear track), and dimensions of the MGB kingpins. I kept the lower A-arms horizontal, and set the angle of the upper A-arms to approximate the MGB's front roll center. There wasn't much more to it than that. I didn't do any analysis to see if the camber curves changed, but I don't expect them to be much different.

Since the Sprite kingpin is shorter than the MGB's, I think the upper pickups would have to be lower than shown in these drawings. For comparison, the MGB swivel axle is 8-3/4", hole-to-hole, and the height distance between the upper and lower pickups is 7".


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 Post subject: Re: Nick's MGB Build
PostPosted: February 16, 2012, 10:50 am 
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god bless you!


nick47 wrote:
Not sure it's as detailed, but here's what I've got.

Image

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 Post subject: Re: Nick's MGB Build
PostPosted: February 18, 2012, 6:48 pm 
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A couple of weeks ago I got the donor running for a few seconds with fuel poured into a funnel. I figured once the fuel pump was fixed I'd be good to go. Unfortunately there was a little more to it than that. Even with a good fuel pump, I couldn't get the engine to run for more than 15 seconds before it would quit. I fiddled with the car off and on for the past two weeks with no luck, then finally gave in and overhauled the carbs.

Image

Turns out they were in terrible shape. Full of gunk, float levels way off, just a mess. How the car ran at all is a mystery. Anyway, with the rebuilt carbs, the car started on the first turn of the key and idled smoothly. I let it warm up, adjusted the carbs using the hose and screwdriver method, then took the car for a drive down to the park. It ran flawlessly, started immediately each time I turned the key, and had plenty of power. What a great car. Time to take it all apart now.

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Note to self: When Gonzo suggests a carb rebuild, rebuild the carbs.


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 Post subject: Re: Nick's MGB Build
PostPosted: February 18, 2012, 6:50 pm 
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mmmm...nothing like the smell of old gas and bad SU carbs.....

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 Post subject: Re: Nick's MGB Build
PostPosted: February 21, 2012, 4:00 pm 
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Nick.


I blew your suspension drawings up to real size and made a top wishbone with a few differences. I'm using 5/8-18 threaded heims so my tubing is a little beefier. Originally I was going to put a 3/4" bolt where the upright bushings would normally be. In the end I turned a steel plug with a half inch holed bored on center and welded them in place which will hold the heims. Since I won't have to worry about damaging the rubber, I didn't split the tube in the middle od hte wishbone or need to use a bolt to clamp them together. I jigged up the wishbone. Everything except the weld quality came out well. I figure the first one was for practice. I'll make better ones with my Tig welder. By the way, mounting the pickups with 5 degrees of caster was extremely easy with your drawings. I double checked everything with a compass style level from ACE hardware. I simply ran threaded rod through the pickup points and put the level on top...5 degrees every time.

Thanks for your help! I owe you one! I'm awash in MGB stuff I won't need. Let me know if you need anything and I'll send it along.

JDD

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 Post subject: Re: Nick's MGB Build
PostPosted: February 21, 2012, 4:49 pm 
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I'm glad it helped. You're now officially part of my Locost moral support team. You keep building and I'll keep building.


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