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PostPosted: July 5, 2010, 10:11 pm 
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In reference to the original question (Solid Front Axle - Anyone thought about using one?) may I suggest...Ray Caldwell! I had the pleasure of working with/for him on an aviation engine development project when he was president of Kitfox and we talked a bunch about the D-7, his beam axle geometry (front and rear) Can-Am car. I wish I could find more about its history (like suspension drawings maybe?) but here's this from (of all places) SimpleSevens.org (they're the diametric opposite of locostusa.com, their motto is "in the interest of genuine Lotus Sevens and their owners").

Here's their page on it:
http://www.simplesevens.org/DSK/history/dsk02.htm

And about 1/3 of the way down the page there's some discussion of it on f1technical.com thread:
http://www.f1technical.net/forum/viewto ... =87939&f=4

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PostPosted: July 5, 2010, 11:26 pm 
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JackMcCornack wrote:
In reference to the original question (Solid Front Axle - Anyone thought about using one?) may I suggest...Ray Caldwell! .......................

Here's their page on it:
http://www.simplesevens.org/DSK/history/dsk02.htm

And about 1/3 of the way down the page there's some discussion of it on f1technical.com thread:
http://www.f1technical.net/forum/viewto ... =87939&f=4
Excellent links Jack. TNX

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PostPosted: July 8, 2010, 3:27 am 
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JackMcCornack wrote:
In reference to the original question (Solid Front Axle - Anyone thought about using one?) may I suggest...Ray Caldwell! I had the pleasure of working with/for him on an aviation engine development project when he was president of Kitfox and we talked a bunch about the D-7, his beam axle geometry (front and rear) Can-Am car. I wish I could find more about its history (like suspension drawings maybe?)


I see the car has been restored Jack so somebody owns it somewhere who probably has resto photos etc..

http://www.conceptcarz.com/vehicle/z113 ... l-D-7.aspx

http://www.racingsportscars.com/photo/1 ... 17-001.jpg


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PostPosted: July 13, 2010, 7:57 am 
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Is this a straight front axle in a Lotus 6(six)?

http://www.simplesevens.org/0058pics/005801.jpg

I didn't think a straight front axle ever went in a lotus.


Mark...


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PostPosted: July 13, 2010, 8:19 am 
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I think the Six used a Ford Anglia front axle. Very similar to the typical early Ford beam axle, but smaller.

Lots of great pics at http://atspeedimages.com/search.php?s=1955+Lotus+mk+VI

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PostPosted: July 13, 2010, 10:17 am 
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MustangSix,

Wow, thanks for that link. I love the way this car looks. A little more eligant than most. I like the rear body work and how the rear fenders attatch. Thanks!

Mark....


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PostPosted: July 13, 2010, 10:25 am 
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MustangSix wrote:
I think the Six used a Ford Anglia front axle. Very similar to the typical early Ford beam axle, but smaller.

Lots of great pics at http://atspeedimages.com/search.php?s=1955+Lotus+mk+VI


Nah, its swing axles pivoted in the middle, see the pictures of the 2 front wheels with savage positive camber and jacking that are around the net.

Image

The only time Lotus used a beam was in 1968, the Lotus 58 as I mentioned.

F1 may have been different had Jim Clark tested it the week after he was killed. Hill tested it some time later and was faster but didn't like it for some reason and then wings hit big time and thats where all development went.


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PostPosted: July 13, 2010, 10:43 am 
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Cheapracer wrote:
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Nah, its swing axles pivoted in the middle,


I think I remember a "hot rod" conversion for Model A's or maybe the V8 coupes that involved cutting the beam axle in two pieces and attaching the halves to the frame in the center.

Wonder what those were like goin' round corners???

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PostPosted: July 13, 2010, 10:45 am 
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I stand corrected, sort of. It was definitely split into a swing axle, but from what I can gather it did start out as a Ford axle. I think early Elevens used the same swing axles, too.

I wonder how those are to drive? Must get exciting as the inside axle begins to jack the front of the car!

OTOH, Ford trucks and vans have used swing axles for years. Not known for handling, but neither do they have a rep for being scary.

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PostPosted: July 14, 2010, 12:06 am 
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Here's a link to a thread on another site from many years ago. Bob Sheaves is obviously an expert on solid front axles. They are talking about truck axles but get into racing also.

http://www.race-dezert.com/forum/archiv ... t-288.html

I have to admit I never noticed the various evils he points out about a solid front axle (maybe he's thinking of heavier truck axles with more unsprung weight than a car). I did notice roll steer though. That was caused by the way the axles were attached to the car by the wishbones. A rear roll bar (definitely not stock) helped a lot.

My '40 could do 120 MPH on the typical country roads of the 50-60s (usually narrower than a typical suburban street, a lot of crown and rough to boot). It's surprising how bumpy a nice looking stretch of road can be at 120. You normally drove in the middle of the road and pulled to your side when someone was approaching.

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PostPosted: July 14, 2010, 12:18 am 
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GonzoRacer wrote:
Cheapracer wrote:
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Nah, its swing axles pivoted in the middle,
I think I remember a "hot rod" conversion for Model A's or maybe the V8 coupes that involved cutting the beam axle in two pieces and attaching the halves to the frame in the center.

Wonder what those were like goin' round corners???
About like an early Corvair if you attempted to corner too fast. :ack:

NOT a nice experience I can tell you! I was used to a 911 Porsche and I decided to take my wife's Corvair one day. Corvair no corner like 911! :oops:

The Corvair and I both survived (barely).

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PostPosted: July 14, 2010, 12:33 am 
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MustangSix wrote:

I wonder how those are to drive? Must get exciting as the inside axle begins to jack the front of the car!

.


Not so bad as a Corvair or VW rear because the pivots are very close together so jacking leverage is near zero unlike a Corvair/VW where you have 1'+ of leverage.

The earlier 50'/60's/70's Mercedes had a swing axle rear but the pivots were just one central so it didn't jack. They were noted for their good ride and good handling.

Image


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PostPosted: July 14, 2010, 12:12 pm 
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cheapracer wrote:
MustangSix wrote:

I wonder how those are to drive? Must get exciting as the inside axle begins to jack the front of the car!.
Not so bad as a Corvair or VW rear because the pivots are very close together so jacking leverage is near zero unlike a Corvair/VW where you have 1'+ of leverage.

Off hand I think the amount jacking leverage force is mostly due to the distance between the tire patch on the ground to the other end of the axle in relation to the height of that pivot point above the ground. While the length of the axles etc would be different between Corvair, VW and MB, I don't think the separation of the pivot points (themselves) between the various axles would have as much affect as all the other factors of the geometry (including the height of the pivot point above the ground).

The earlier 50'/60's/70's Mercedes had a swing axle rear but the pivots were just one central so it didn't jack.

As I remember it the pivot point was under the differential. That would lower the imaginary line from the tire patch to the pivot point of the "axle". Lowering the pivot point helps but shouldn't eliminate jacking.

So yes the MB method was an improvement over the Corvair et. al. but the defect in the design still exists.


They were noted for their good ride and good handling.
I'd rather not have my front (or rear) suspension look like this in a turn!
Attachment:
1951 J2 Allard-sml.jpg


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PostPosted: July 16, 2010, 9:25 am 
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The photo of the Allard is a perfect example of swing axle "jacking". Add early Spitfires to the swingaxle list.

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PostPosted: July 16, 2010, 10:18 am 
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True, however any suspension design with a High Roll center and short VSAL (Virtural swing arm length, which on a swing axle is exactly the length of control arm), will exhibit identical characteristics as that Allard. For swing axle the RC is at the intersection of the line through the contact patch and the inner pivot of the Control arm and the center of the car, so if the arms are short with wide spacing between pivots, and at the axle center line (which is typical) your RC can actually be ABOVE the axle centerline! Swing axles if designed correctly can behave decently if the inner pivot provide a low enough roll center to minimize jacking forces, and the arms are of reasonable length. Still a VSAL of 1/2 your track width is awful short, I tend to design rear suspension VSAL's in the 80-100" range or longer, and fronts ~140% of that. I'd think you could have good luck using a modified ford I-beam type front suspension to get longer arms, lower pivots, and a SLA type RC location. However at that point I'm not sure you would have much if any of a weight savings compared to a SLA suspension, nor would you have a huge advantage over a traditional Beam axle.

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