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Learning how to build Lotus Seven replicas...together!
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PostPosted: August 26, 2008, 11:16 am 
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Joined: June 11, 2008, 1:31 pm
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Location: Denver,CO
Well after a bit of not posting I have minor updates. I decided to do the finish welding on the majority of the car. This proved to be very time consuming and well time consuming. Two bottles of gas later and I'm done. At least with the basic frame.

Still looking for my miata I press on undanted and have started on some aspects of the front suspension. I made pvc simluators, at least the ends. And using 16g steel cut out patterns for the kineticvehicles control arms.
I'm not sure how Jack would feel about this but using the drawings provided on the website http://www.kineticvehicles.com/ I found that I could simply scale them using photoshop and print them out. From there I could cut a paper pattern and transfer it to the steel. I will get the remained of the steel to make my own simulators for the front suspension.

I was talking to my neighbor how works with granit who told me he has access to a water jet and can scan my 16g steel mockup and use it to cut the real steel and he wouldn't charge me. Perfect.
Pics of the simulators etc and some of the extra bars added.

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Next up was my latest ebay find. I remeber a guy finding some appleton racks for $75 on ebay a while back. Well I found a Southwest Speed rack with a 1.75 ratio for $75 with shipping. Its 18.25 from center to center. Should work out nicely.

Next up is to order heims and brackets from
http://www.kineticvehicles.com/ and then by some steel to work on the control arms.

I guess I'm working backwards of many people that start with the rear and work their way forward.

evo


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PostPosted: August 26, 2008, 4:16 pm 
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Joined: February 17, 2008, 2:04 pm
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Cool, our frames look almost identical. I started with the rear first... but mines solid. This is good because now I can steal some ideas from your front suspensions when I'm done 8) Looking good-

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PostPosted: August 27, 2008, 8:32 pm 
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Location: Denver,CO
Just for reading sake I decided to by a suspension book.
How to Make Your Car Handle - Fred Puhn

Maybe this will help me to build a decent suspension that works.

evo


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PostPosted: September 1, 2008, 12:19 pm 
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Location: Denver,CO
Over last week I purchased a few bits of steel. Mainly for making parts of the Kinetic suspension brackets etc....

The big yellow square tube I'll use for engine mounts. I figure 1/4" should be enough. Also got some tubing that I'm not sure I can use. Manily 3/4" 16g tube maybe for the steering collum (I may want thicker not sure) and some 2" .105 tubes. (Not sure what I'll do with them)

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Also is a pic of my battery, being charged by solar power. (very slowly like .3v per day from a 1.5v HF solar charger)
I really need to buy a donor car to get rolling. Its a shame miatas are hard to come by cheap here.

evo


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PostPosted: September 1, 2008, 5:27 pm 
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evo626 wrote:
I'm not sure how Jack would feel about this but using the drawings provided on the website http://www.kineticvehicles.com/ I found that I could simply scale them using photoshop and print them out. From there I could cut a paper pattern and transfer it to the steel.
Jack would feel just great, they're there to be easy to copy. Scaling is important, not only on the drawing-to-print axis, but also the print-to-printer. I print a 5 x 5 square on any new printer I get, measure it, and write the conversion factor on the inside of the ink door, e.g. 1.014" on document =1" on printer. When I want a precise print, I scale the drawing up by 1.014.

Also, I make a lot of positioning/fit test parts ut of card stock, just print them and cut them out; bend as needed (no brake required) and bolt them to the chassis.

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PostPosted: September 4, 2008, 2:02 pm 
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Well got a few things done. First off recieved my southwest speed rack in the mail. Cleaned it up and it looks good and moves smoothly.
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Next I cut and cleaned some of my bulk scrap steel for my control arms. Came out looking really nice, like new steel. A wire wheel on my angle grinder did wonders. Here is a pic of the old versus new.
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Then I went to a local Fastenal store and ordered my DOM tubes for the control arms and the 2-1/2"X1" tube for the lower arms. I'm going to use swaged tubes for the non-weld top tube.

And I'm in contact with Kinetic with ordering some parts. Just need a final price on 1/2 clevis and I'll order that.

evo


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 Post subject: Mania metal cutting
PostPosted: September 12, 2008, 9:57 pm 
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Well I ALMOST bought a miata but the buy opted out. Disappointed I looked at another miata which turned out to be a train wreck.....Literally. It was the most mangled trash heap Ive seen in a while.

So I decided to hold off on buying the car until I find a screaming deal.

Anyway I recieved some items from Fastenal and started work on my Kintec style control arms. I learned alot about drill metal this week. Took two days to make the lower control arm bungs and then just drill out the bottom of the upper control arm outboard part. I'll tell you this, your better off buying the Kintec control arms than making them. What a PITA to do and I'll maybe save $100.

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While I was at it I finshed my templates for the other parts I need cut. (Yes one is made of wood, just because it was easier to cut that way.)

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I ordered the wrong thickness 3/4" tube, got .120 and needed .188 for the control arms. So I'll use the extra piece for my steering shaft. Ordered a new piece off of ebay. Speaking of ebay I went mad and ordered a left side miata spindle and 2x lower ball joints . Also ordered some taps and drill bits.

I think I'll order some upper balls joints as well. I read the thread on them and will use the moog part #.

evo


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PostPosted: September 12, 2008, 11:24 pm 
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Nice progress, evo! Looks very similar...I did the same thing and realized that Jack's asking price is impossible to beat if you credit yourself minimum wage for your time. Doing it over, I'd probably just order the kit, or at least the bungs.

For the plate pieces you're getting ready to cut, use the straight edges of your metal stock for the straight edges of your parts. Theirs will end up straighter, and you'll probably get more parts out of your stock. But most of all, it's less cutting for you.

Depending on how you're doing your cutting, consider stacking your flat stock, tack the edges, then cut all four pieces at once. While it's not critical that these pieces match, it might save some time. I would definitely drill the holes in a stack. Don't do that until you've test fit the pieces on the arms. Alternately, clamp the plates to the legs and drill through the assembly all at once.

When you put the spacer inside the 2.5" tube to support the ball joint bolt, do yourself a favor and tack it in place. If you over-drill the hole in the 2.5" tube, or maybe drill another small hole next to it, you can tack it from the outside. You can try to tack it inside, but it's a pain to reach, at least with MIG.

I think Kinetic's spacers might be stainless? I'm not sure, but that wouldn't tack to the steel well. I think instead of the spacer, I used a big fender washer so alignment wasn't too critical. That also allowed two small holes 1/2" from the bolt hole for plug welding the washer from below.

Clear as mud? There are pix in my build log if you're interested.

-dave

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...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
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PostPosted: September 13, 2008, 11:16 am 
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That makes perfect sense after I reread it 3 times, lol. I intend to have the plate steel cut with a water jet. Not because I do that sort of thing all the time, but since my neighbor offered to do it for free! lol

evo


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 Post subject: Evo's suspension theory.
PostPosted: September 25, 2008, 8:34 pm 
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Well got some minor work done today. I've been ordering parts like no other lately. Just came in: ball joints and brackets from Kinetic, lower ball joints from ebay, two more spindles for a total of three, some taps and made a device to help with the suspension. I aslo recieved my water cut bracktes. I spent too much on them at $110 and should have bought the lot from Jack :( .


Anyway this is my theory, which could be totally off base.

With the car suspension we must assume there are some constants. Starting with the wheels, the wheels provide a constant for the placement of the spindles as they are attached to the wheels.

The next constant is the track between the two front wheels. This shouldn’t change. Using these two constants we can now solve several other problems with suspension design. The track and the height of the spindles determine the length of the front lower control arm. This arm becomes a base to figure everything else off of. The next “constant” isn’t really a constant but is more of a packaging constraint. The steering rack “should” be in a straight line across for the spindle arms. These correlations change the front lower control arms position either forward or backward.

Ride height is also influenced by the wheel/tire selection. Most modern suspensions with unequal arms have at least one arm parallel to the ground. The height of the lower ball joint on the spindle and the mounting point on the frame should line up. Really the lower rear control arm becomes a constant in the since of the front mounting point will be line with this. Most Locosters seem to put this mount on the lower frame rail. So to get the proper ride height you may have to raise the frame in regards to the ground to get the front lower control arm parallel with the ground.

Once the lower control sizes and locations are made then the uppers seem to fall into place. This is were I run low on theory’s for the upper control arms other than it would seem most have the mounts in the area of 2 inches from the top of the frame. Or they simply make these mounts angle at 15degrees from the top of the spindle to the frame mount.

Anyway here are some pictures of my device which I can use for alignment, camber, toe, and caster (with the proper gauge). It is simply a board with holes drills for the spindles to mount to. Using a hinge I can adjust camber by moving the board inward. It uses a door stop to control the angle. Very low tech. Now my question with such a device is from where is the track measured.? Is it from the outer edge of the tires or from the spindles?

On with the pics:
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evo


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PostPosted: September 27, 2008, 6:18 pm 
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Today I put a bit of effort into the front lower control arm. Its length from the frame (with brackets, ball joints etc) came to 18 inchs to the center of the ball joint. My system is working so far, but I found to get the lower control arm somewhat parallel to the ground using my wheel/tire combo I had to rasie the car too a ride height of 5.5inchs.

Even at this height the lower control arm is still at a 5degree angle refference the spindle. My front track is going to be 59.1. From what I'm reading with my 17x7 tires which have a 25offest the rear end of the miata subframe will come out wards closer to 57.3 or more depending one who you ask the rear track to be.

Anywho on with the pictures. I have work tonight so it will be another 4 days before a minor update.

Image
Image


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PostPosted: September 29, 2008, 11:01 am 
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The steering rack “should” be in a straight line across for the spindle arms. These correlations change the front lower control arms position either forward or backward.


Not true! The tie rod ends must be in line with your pivots, and in proportion to your pivots to avoid bump steer. Search for "Bump steer" here or via Google and you'll find exhaustive explanations. Here's a decent discussion for starters: http://www.locostusa.com/forums/viewtopic.php?t=4050

For Miata spindles, you're in a bit of a bind because the rack wants to be in the same place as the lower control arm. You've got a few choices: 1) fudge it; 2) put the rack out front; 3) move the outer tie rod ends to the top of the steering arm.

I chose option 3, and I recommend it. If you can borrow the reamer ($100 worth), it's very locost, easy, and yields a very good solution.

You can also weld/bend the steering arm, but that seems like a very contentious topic so I won't mention it here. Oops...I shouldn'ta said that.

Quote:
Once the lower control sizes and locations are made then the uppers seem to fall into place. This is were I run low on theory’s for the upper control arms other than it would seem most have the mounts in the area of 2 inches from the top of the frame. Or they simply make these mounts angle at 15degrees from the top of the spindle to the frame mount.


Again, it's not that simple. Check out the stickies in the Suspension section (http://locostusa.com/forums/viewforum.php?f=5) and buy one of the recommended books ($30 or less).

Quote:
Anyway here are some pictures of my device which I can use for alignment, camber, toe, and caster (with the proper gauge).


Hey, I like your gauge, Evo. Wish I'd built something like that when I did mine.

Quote:

Now my question with such a device is from where is the track measured.? Is it from the outer edge of the tires or from the spindles?


To the center of the tread. If you've got your wheels and tires, just mount and measure. If not, you'll need to figure out the tire size, wheel size, offset, etc. to correlate the spindle to the track. I think there are some online calculators that crunch the numbers for you.


Looks great, Evo...You're going to end up with a good car! Keep us posted,
-dave

ps. How about posting larger pictures in the future? I can't even make out what some of them are without clicking through.

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...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
Visit my [Locost 7 build log]


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PostPosted: September 29, 2008, 9:46 pm 
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Thanks! I appreciate the feedback.

As for my statement on the rack, that’s what I meant but over simplified what I was trying to say. I plan on reaming out eh spindle and putting the outer tie rods on the top of the steering arms.

I miscalculated my wheelbase at 59.1 and now have it set at a cool 57 inches. I’ll start posting bigger pictures next go round.

Thanks!

evo


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PostPosted: October 3, 2008, 9:57 pm 
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Well just finished building the front lower control arms. What a task that was. For the inner washer I used a 1/2 fender nut and welded tabs to it to make up to .20 difference.

I got both sides done. Using pvc for the rear . My wheelbase is at 57inchs and so far everything is lining up the way it should. The white pvc in the picture is just showing aprx height of the rack and pinion. Just need to order upper ball joints so I can do the top control arms.

Image
Image


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PostPosted: October 4, 2008, 3:38 am 
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Forgot to add I also picked up another book: Chassis Engineering By Herb Adams. Pretty good basic suspension/chassis book.


evo


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