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Learning how to build Lotus Seven replicas...together!
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PostPosted: May 1, 2006, 4:10 pm 
Got the bodywork from Coveland7. They are the only place that makes custom Aluminum fenders that I've found. They also have two different nosecones available.

Check them out at www.coveland7.com Shipping was about $40 for everything from their location in the northeast US to Arizona.


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PostPosted: May 1, 2006, 4:13 pm 
"He was concerned about kingpin offset, not Ackerman which a separate issue."

Yes it is a different issue and the 15 degrees he has is quite alot and may cause some handling problems. Of course there are many was to set it up, but here is one. http://www.pbase.com/paulgreen/image/39943100
It has the added benifet of rotating the spindle to raise the steering arm to avoid contact with the rear leg of the lower control arm.


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PostPosted: May 1, 2006, 4:16 pm 
kb58 wrote:
In the 60s and 70s it was common practice to heat the steering arms with a rosebud and bend them to where you want.


That might be an option. Also, since they are forged steel knuckles, I could always cut and reweld with a bit more of an angle to the arm. :?:


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PostPosted: May 1, 2006, 4:21 pm 
"They are angled, persay. This angle allows one to place the tie rod on top of the arm (which moves the rod end up and outward) and essentially eliminates the preset ackerman. "

Well I can tell you for sure that's not the case because I moved my tie rods to the top (same spindles) and my car has ackerman very close to an original 240sx. (I have another 240 and measured it.)


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PostPosted: May 1, 2006, 4:21 pm 
The woodward manual steering unit is a pretty good one, but mine is front steer.


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PostPosted: May 1, 2006, 4:26 pm 
Paul.. I just realized that you are also doing a 240sx based build after looking at your pbase album.

I like your solution for the upper balljoint. very clean! I dont have access to equipment to make the cleanly machined parts you did, but I may try to do a similar arrangement, placing the joint above the two bolts on the knuckle.


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 Post subject:
PostPosted: May 1, 2006, 4:28 pm 
PaulG wrote:
"They are angled, persay. This angle allows one to place the tie rod on top of the arm (which moves the rod end up and outward) and essentially eliminates the preset ackerman. "

Well I can tell you for sure that's not the case because I moved my tie rods to the top (same spindles) and my car has ackerman very close to an original 240sx. (I have another 240 and measured it.)


How high up off the arms are your tie rod joints? Also, it depends on where you locate the upper balljoint and what kind of kingpin inclination you are running.. It all affects ackerman apparently.

Regardless, this is a good discussion. I've got some pretty serious issues that I'll have to work out. I have to stick with front steer, as I dont believe that I have room for a rack in front of the engine, and I have that nice woodward unit coming.


Last edited by datz510 on May 1, 2006, 4:32 pm, edited 1 time in total.

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 Post subject: Ackerman
PostPosted: May 1, 2006, 4:30 pm 
I dont have any good pic's of it, but you can see here that I've got the tie rod ends on top and even though I don't have any photos of it with the wheels turned, the toe out is real close to the original 240.
Image


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PostPosted: May 1, 2006, 4:37 pm 
I've got 2-3 sets of knuckles, so I may just chop them up tongiht and see if I can make a set with the proper arms. I've had good luck welding forged steel in the past, so it would be worth a try at least.

If that doesn't work, it looks like I'll need to go junkyarding this week and see what I can find. Really hate to scrap all I've done on the frontend, but if there's no other way, it kinda looks like I may have no choice.


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PostPosted: May 1, 2006, 4:43 pm 
Quote:
So, I'll have to figure out how to solve this. Either come up with a way to get the tie rod ends outboard of the pivot axis or swap out knuckles to something that will be more suitable. I'd hate to have to redo my A arms though. Any ideas?


Does it have to be front steer? If so, I don't see how you could ever get those to work. I wanted to set mine up front steer also but didn't want to mix and match any more than I had to. As it turns out, I had to use a Toyota Tercel rack because the 240 rack was too long for bump steer.


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PostPosted: May 1, 2006, 4:47 pm 
I've got $400 in the woodward rack now and my engine sits too far forward to place a rack in front of it (between it and the chassis uprights, like yours).

I'm going to try doing some cutting and welding tonight to see if I can come up with a reasonable solution. It looks like I could just lop the arm off, rotate 180 degrees and weld them back on, even adding additional ackerman angle if I wanted to. Then add a little gusseting on the sides for safety reasonas and it might work.


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 Post subject: Ackerman
PostPosted: May 1, 2006, 4:50 pm 
[quote] the actual Ackermann factor varies in a complex way with the arm angle, rack length, rack offset forward or rearward of the arm ends, whether rack is forward or rearward of the kingpins, and with the actual mean steer angle. Moving the rack forward or backward to change the tie-rod angles can be a useful way to adjust the Ackermann factor,

Well I stand corrected on this. But remember even though moving the rack up and down has more effect on bump steer, moving it for and aft will change it some. So now your moving the rack around trying to get the Ackerman right and the bump steer also. It's more than my brain can handle. :P


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PostPosted: May 1, 2006, 4:54 pm 
Yep, it does have an effect, but you were right as well in that with zero ackerman in the knuckles, moving the rack will not add ackerman angle. So, I think we both stand corrected! Learn new things every day. I am glad that someone spotted these errors, as I could have been a lot further into the build.

I am going to try cutting and welding the arms and see how that turns out. The welder I have is more than adequate for the penetration needed and I am confident enough in my welding abilities to take it on. If that doesnt work, I have several more sets of 240 knuckles laying around..


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 Post subject:
PostPosted: May 1, 2006, 5:00 pm 
Quote:
How high up off the arms are your tie rod joints?
Same as they were when mounted on the bottom. I welded up the hole and reamed the taper from the top side.

My KPI is around 10 degrees. If your interested, I have a Suspension3D file.


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PostPosted: May 1, 2006, 5:09 pm 
Welding should work fine. As you said, flip them over and that should give you some Ackermam (how much??????) and also move the tie rod on top.

As long as you feel you can get a safe weld, go for it. If not, heating and bending might be safer but it would be tough to get them the same.


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