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Learning how to build Lotus Seven replicas...together!
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PostPosted: Fri Jul 16, 2010 10:19 am 
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MustangSix wrote:
Add early Spitfires to the swingaxle list.

oh boy no kidding!! the jacking effect is what defined the outer limit of traction for me, once i learned to stay under that point i was fine but before then? weeeehaWWW where's my hat! ya gotta have a finely tuned gluteous mass deflection sensor array though, i couldn't do it anymore.

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PostPosted: Fri Jul 16, 2010 1:49 pm 
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MustangSix wrote:
The photo of the Allard is a perfect example of swing axle "jacking". Add early Spitfires to the swing axle list.
And it looks like the Allard has a strap from near the backing plates up near the headlight mounts to restrict the amount the axle can drop. I'd hate to see the result if one of them let loose in the middle of a turn!

My Renault Dauphine (swing axle) had a heavy canvas looking strap that went from the body work around the axle and back up again as a limit to the axle drop. The old VW swing arms used to contact a lip under the swing arm as the stop.

Just to set the record straight though, we were talking about solid axles but it is interesting to see what happens when you mess with mother nature. :)

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PostPosted: Tue Jul 27, 2010 4:16 pm 
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Location: MILE HIGH
kf2qd,

HERE ARE A FEW LINKS FOR USED MIDGET, SPRINTS AND SILVER CROWN ITEMS, WHERE YOU CAN GET A CHEEP FRONT AXEL SHOULD YOU GO THIS DIRECTION.
ASPHALT CARS, LIKE THE SIVER CROWN CARS USUALLY USE 2 FRONT BRAKES

http://hoseheadsclassifieds.com/
http://www.racingjunk.com/

I'VE BEEN CONSIDERING THIS DIRECTION ALSO..... BUT, TILL I SELL MY KIDNEY.
http://www.locostusa.com/forums/viewtopic.php?f=53&t=9208


AND FOR ALL THE EUROPHILES HERE...... GET OUT OF THE SUN AND STOP WATCHING THE JUMBO TRON, AND GET YOUR DIRT ON.
http://www.youtube.com/watch?v=XdxCyRsDjYU
http://www.youtube.com/watch?v=76OK0mySmdk&feature=player_embedded
http://www.youtube.com/watch?v=okpj28E55U4

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Last edited by HUFFSTER on Wed Jul 28, 2010 11:22 am, edited 1 time in total.

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PostPosted: Wed Jul 28, 2010 4:33 am 
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THANKS HUFFSTER!!


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PostPosted: Thu Aug 05, 2010 11:38 am 
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Here's a lot of detail of how a guy converted A arms to a solid front axle. There's lot's of good info that might be useful for picking and matching parts.

http://www.jalopyjournal.com/forum/show ... p?t=230636

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http://dmr-architect.com/~locouki/


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PostPosted: Sun Aug 08, 2010 12:20 pm 
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A friend of mine suggested I take a look at your site (since my name was mentioned...LOL) and am impressed with the effort you guys show.

If you have specific questions for me, feel free to ask away.

Best regards,

Bob


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PostPosted: Tue Jun 21, 2011 4:44 pm 
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MustangSix wrote:
YIf they are a bit off, you break out the big adjustment bar and you tweak it into shape.


That's how big-truck alignments are done. They chain the beam to the chassis and break out the bottle jack, or use the floor anchors and hydraulic pullers.

There's such a place a few towns over, that is also the go-to place for people with beam-axle Econolines, street rods, etc. Back in the day, they also aligned those newfangled MacPherson struts; on my autocross Capri, they bent the forged knuckles to give me more negative camber without slotting the strut mounts, which wasn't legal in the class I was running in.

Quote:
If your KPI or caster is off by a quarter degree, I don't think you would ever notice.


Some OEMs (older Chryslers come to mind) have separate left/right side alignment specs that differ by more than that.


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PostPosted: Sun Jun 26, 2011 7:34 pm 
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Location: Melbourne, Australia.
The ancient solid forged steel beam axle has two fundamental problems, very high weight, and the narrow based king pin arrangement allows the wheels to flap about, once the very highly loaded king pin wears a little bit loose.

But how about a pair of modern ball joint steering knuckles, with a PAIR of light upper and lower thin wall tubular beams as a single rigid structure ?
With care, I am sure it could be built as light and as rigid as an IFS.

If you are planning on very wide, very low profile front tires, they would remain vertical to the track, and there would be zero front track width change, over extreme suspension movement and body roll.

You can even place the front roll centre below ground level if you wished to do so, by locating it laterally with a Mumford linkage.
viewtopic.php?t=77

Dare to be different !!!


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PostPosted: Sun Jun 26, 2011 10:36 pm 
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Warpspeed wrote:
The ancient solid forged steel beam axle has two fundamental problems, very high weight,

Use a tubular axle.

and the narrow based king pin arrangement allows the wheels to flap about, once the very highly loaded king pin wears a little bit loose.

I would be more concerned that a solid front axle can't be designed to have camber variability under bump/droop. Most cars that used a solid front axles weighed 2-1/2 to 3 times that of a Locost. And bushings aren't that hard to change.

But how about a pair of modern ball joint steering knuckles, with a PAIR of light upper and lower thin wall tubular beams as a single rigid structure ?
With care, I am sure it could be built as light and as rigid as an IFS.

Sort of like the early VWs? :lol:

But certainly not as simple as a singular tubular axle. For one thing you have to provide room for two beams to move around in the frame.

How 'bout one hollow beam axle similar to this?
http://www.speedwaymotors.com/Front-Tub ... ,2127.html


If you are planning on very wide, very low profile front tires, they would remain vertical to the track, and there would be zero front track width change, over extreme suspension movement and body roll.

Do you really want the tires to remain vertical to the track under racing conditions? [i.e. not at the drags].
[snip]

Dare to be different !!!

We are getting pretty far off the original question/idea, which was,
kf2qd wrote:
(snip)
I am thinking of a Locost as a daily drive and not as a perfoemance vehicle, something fun to drive back and forth to work. Reliability being the main idea.
So high loads, wide tires etc are not really that important in this case.

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Completed building GSXR1000 CMC7, "Locouki"
http://dmr-architect.com/~locouki/


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PostPosted: Sun Jun 26, 2011 11:35 pm 
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The only purpose of camber variability is an attempt to keep the heavily loaded outside wheel vertical as the chassis rolls in that direction. A beam axle does that automatically.

A single large diameter "hot rod" type tubular beam axle still suffers from having a narrow based king pins of some type.

The modern wide spaced ball joint steering knuckle is an excellent solution to the old original king pin design, with all it's problems.

What I am suggesting is a slim upper beam to tie the two top ball joints together, and a slim lower beam to tie the two lower ball joints together, and both beams rigidly triangulated together into a stiff bulkhead type of structure.
If thin wall tubing were intelligently used, the whole thing could be made extremely stiff and very light weight.

I have never seen anything like that on a Volkswagen, don't know what you mean there ???

Sure it would take up more vertical room, but the type of car we are discussing here has the front wheels ahead of the engine where there may be sufficient space to do it.


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PostPosted: Mon Jun 27, 2011 1:12 am 
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Warpspeed wrote:
The only purpose of camber variability is an attempt to keep the heavily loaded outside wheel vertical as the chassis rolls in that direction.

I believe it is more accurate to say that it attempts to keep the tire patch flat on the ground as the cornering forces build up. The tire flexes under cornering forces and the the tire patch on the ground loads the outside edge more than the inside edge. Therefore it is desirable (which is possible in an IFS) to -change- the camber to compensate for that (and to try to correct the roll induced camber change also).

A beam axle does that automatically.

A beam axle maintains what ever camber you have built into the axle. It does not compensate for the tire deforming under side loads. That is the problem with the beam axle when pushed to the limit. If it was so good then F1 cars would probably still be using them.

For instance, the 1946 through 1948 Ford solid axles had 0 to +1 degree of camber. That might not be the correct amount to have as the constantly changing cornering side forces build up. A camber changing designed IFS suspension can induce "non vertical" changes in the wheel to keep the tire patch flat on the ground as the car rolls due to the same forces.

The stock tires back then were pretty narrow so the deformation wasn't as bad a modern tires. But after awhile you could see that some rows of blocks running around the tire were worn more than the rows next to them because of tire deformation.


A single large diameter "hot rod" type tubular beam axle still suffers from having a narrow based king pins of some type.

That's the advantage of building your own. Don't use a large [heavy] axle and make the king pin length the ID of your rims if that's what turns you on. Personally for all the miles put on the old Ford king pins I think they would work fine in a light Locost (if you could even find/make a light spindle to go along with the king pin. The twin tube axle seems to be solving a problem that a Locost wouldn't have.

The modern wide spaced ball joint steering knuckle is an excellent solution to the old original king pin design, with all it's problems.

What I am suggesting is a slim upper beam to tie the two top ball joints together, and a slim lower beam to tie the two lower ball joints together, and both beams rigidly triangulated together into a stiff bulkhead type of structure.
If thin wall tubing were intelligently used, the whole thing could be made extremely stiff and very light weight.

As the movie said, "If you build it, they will come." If nothing else, to SEE the axle. :)

I have never seen anything like that on a Volkswagen, don't know what you mean there ???

The old bug had two round "axle" tubes that ran crosswise to the chassis. I had this picture of unbolting the tubes and converting them to the twin tube axle idea. [It was a joke.]

Sure it would take up more vertical room, but the type of car we are discussing here has the front wheels ahead of the engine where there may be sufficient space to do it.
On a "book" chassis there is 11" between the front frame rails. If we allow 1" of clearance for the minimum clearance between the top and bottom of the axle(s) so they don't hit the chassis, that leaves 9" max from the top of the upper tube to the bottom of the lower tube as the maximum axle(s) separation dimension. Whatever you can take out of the 9" will be the bump/droop the axle(s) can move. If you want 2-1/2" up/down as the max suspension movement (5" total) you are back to about the length of the Ford kingpin (4"). :cry:

It just seems to be easier to use one tube and make the distance between the ball joints as large as you can to fit into the rims if that is the end result desired.

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Completed building GSXR1000 CMC7, "Locouki"
http://dmr-architect.com/~locouki/


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PostPosted: Mon Jun 27, 2011 2:16 pm 
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olrowdy_01 wrote:
A beam axle maintains what ever camber you have built into the axle. It does not compensate for the tire deforming under side loads. That is the problem with the beam axle when pushed to the limit.

If it was so good then F1 cars would probably still be using them.


It most certainly does compensate for it via using caster. You turn the steering and you gain neg camber. The problem with a solid beam is that same "neg camber giving caster" also at the same applies the incorrect amount of camber to the inside tyre and while not as important does take away some of the beam's advantage.

Read more on the Championship winning Welsor Clubman car on one way to solve that inside wheel camber problem ...
http://forums.autosport.com/index.php?s ... or+is+flat
(Clubmans are very similar to Locosts by the way)

I have totally resolved the problem with my own unique design and now presently have the worlds first semi-independent beam that gives all the benefits of both beam and IFS without the drawbacks of either including weight.

Aerodynamics do not allow for beams in F1, nor do the rules now and please note that the last serious pre aero/winged Lotus was actually built with beams at both ends (the 1968 Lotus 58). Clark was due to test it the weekend after he was killed, Hill did and didn't like it much and then the wing race started so it simply got left behind but we had the most successful F1 car designer of the time turning his attention to beams in the hope of getting higher levels of mechanical grip. Personally I don't like the way he did it and it never went down the development path anyway. There was a very interesting Can Am car too with a front beam but I forgot it's name...

The way you reply with quotes to people is very confusing.


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PostPosted: Mon Jun 27, 2011 3:44 pm 
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Caldwell. Sam Posey ran it, but it looked like it was down on power.

I have one very grainy shot of the front end with the bodywork off, but I've never found much else about how the car was arranged.


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PostPosted: Mon Jun 27, 2011 9:28 pm 
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My memory (for what it's worth) of the caldwell was that it was described as having 'front and rear de deions' in its day. I think that camber was adjustable (not under way of course) and recall that there were reported problems with gyroscopic bump steer.

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PostPosted: Mon Jun 27, 2011 10:26 pm 
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One further thought on beam axles and chassis design.
Yes indeed, beam axles take up a lot of room, especially if a lot of suspension travel is required, and it has to cross over, through, or under, the main chassis structure somehow.

Or does it ???

Why does the main load bearing chassis structure have to extend way out beyond the axle centre lines ?
Why not have the chassis end at the suspension pickup points (within the wheelbase) and cantilever the beam axle(s) out beyond the chassis where vertical movement is completely unrestricted?

The crazy hot rodders have been doing this for about a century at the front, it is about the only practical way to get the front of this type of vehicle down really low without losing suspension travel.

If you build a shortened chassis, it will not only probably weigh less, but it completely frees you of any suspension travel constraints regarding getting the steering linkages, drive shafts, or a beam axle, past or through the main chassis structure.

Behold, the classic "suicide" hot rod front end.
Image


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