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Learning how to build Lotus Seven replicas...together!
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PostPosted: January 31, 2019, 10:00 am 
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Nice solution. I've seen an example or two of aluminum pieces done with cove molding bits on the edges, but I've not seen a work piece example as sophisticated as your done with woodworking tool before. Good going.

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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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PostPosted: February 6, 2019, 1:14 am 
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More router success! I realized that I couldn't even rough saw out each upright because my band saw doesn't have enough throat clearance, so I set up the whole plate and rough cut them out with a 1/4" cutter. That went so well I decided to do the whole thing.

Cut time is about 2 hours per side, half of which is my silly 3D filleting.

It needs just a little coolant spray (water and a few drops of Dawn) every 5 seconds or so while roughing and less when finishing. I think I can get a hobby servo to do that part for me.

The outside and center will be removed during the back side operation. Then it's just a matter of drilling and tapping some holes in the ends. The three center holes are tapped right now to hold the part, but will get drilled out for the 12mm bolts for the hub.


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PostPosted: February 6, 2019, 12:06 pm 
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Really nice. I could not do better on my Shopmaster CNC mill.
Paul

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PostPosted: February 9, 2019, 6:01 am 
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One of my key components is coming together. I freaked for a second when the caliper hit the rim, then I realized I don't have the brake hat in there yet, whew! Hopefully that stuff will come in soon, like tomorrow soon.

Oh, my CNC router isn't quite all that, the center hole is out of round maybe 2-3 thou. It's kind of a slanted ellipse, probably X and Y aren't quite square.


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PostPosted: February 9, 2019, 7:38 am 
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Very nice! I imagine you had to sit for hours spraying every few seconds for the part to be produced. A plastic bin, small 110v aquarium pump and hose clip on the drill head would fix that. Need a way to prevent chips from entering the pump.Add a rust preventative to the dish liquid. Most of these little pumps have a knob for adjusting output at the pump and the volume is very low with low pressure (just a trickle) so you should not need splash screens.

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PostPosted: February 9, 2019, 2:51 pm 
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I squirted it by hand on the first one, now I'm getting my system down! An old Basic Stamp and a servo works good. It takes just about the whole bottle for one side. I do intervene a bit while roughing with another squirt bottle. But it lets me do other little stuff around the shop while my shop bitc.....er...shop bot does it's thing. I've got a shallow tray for the drippings as the CNC is mostly wood! Ha.

I think my next project will be a medium sized (24x24x24) CNC built out of steel.

I might have an old aquarium pump around, good call.


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PostPosted: February 13, 2019, 2:54 am 
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Ooh, it fits and spins now! Caliper bracket looks a bit flimsy, maybe I'll remake it beefier.


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PostPosted: February 14, 2019, 6:11 am 
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And the comically oversized lower kingpin bolt goes in. When they find the burnt up mangled wreckage at the bottom of a ravine, this bolt will be completely undamaged. Although the spherical bearing is mounted cantilever, so the bolt is probably only 2 times bigger than it needs to be.


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PostPosted: February 14, 2019, 7:55 am 
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I use a Noga Minicool spray mist on my milling machine and lathe. Works great and is easy to move around (mag base). Adjustable air/mist to minimize mess. About $90 on amazon.


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PostPosted: February 18, 2019, 1:14 am 
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It's super rattley right now without suspension bushings, but it seems like the parts are fitting and working as expected. This is the front left. Depending on how you assemble the upright, steering plate and caliper bracket allow the parts to work on any corner.

I need to finish the steering plates and make some height adjustment "washer/spacer" thingies for the upper and lower pivots.

What's up with the black coating on the wilwood rotor? Am I supposed to take that off before using the brakes?


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PostPosted: February 25, 2019, 4:24 am 
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After a slight distraction with the CVDs I decided my steering rack thing was too complicated and hard to brace the ends. So plan B, miata's other suggestion, I extended the 7/8 rod with 7/8 tubes that I welded ends onto and bolted them to the original steering rod. And then I mangled the outer end to the shape of a clevis. It's only 16 gauge, what do you think? I managed to grind a socket down to fit inside. If I up the tube gauge, I'd go with allen head caps like miata's suggestion.

I'll also add some UHMW bushing supports near the frame rails.


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PostPosted: February 25, 2019, 7:10 am 
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Since the original rack ends will pass through the uhmw bushes, it would have been better to drill a ¼” hole to fit a pin spanner for tightening than to grind flats. Look at coilover seat adjusters and motorcycle preload adjusters to see what I mean. Not the end of the world but I wanted to mention that for those who may duplicate your efforts.

Nice flaring on the ends but the edge distance under the bolt head looks minimal. 16ga might be adequate but I’d weld washers to the outside flanges to reduce the chance of tear out around the bolt. An alternative that would pass through the uhmw bush without disassembly of the rack and make the length adjustable is to use solid 7/8 rod or weld one inch long 7/8 od rod into the ends of the tube, drill and tap, then fit threaded rod into the inboard end and the shank of the male rod end. Just friction cut the head off adequate length 8.8 bolts and debur the cut end. Jamb nuts together on the bolt to have something to clamp to without damaging the threads while cutting the head off and deburring on the bench grinder.

Not clear why you are using colorado axles, but I assumed you were locked-in at this point.


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PostPosted: February 25, 2019, 9:08 am 
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Hopefully you are going to add more structure to support the ends of your rack. You need some type of tube guide, considering the amount of leverage applied to through the steering system. davew


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PostPosted: February 25, 2019, 10:41 am 
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Personally, I would like to see that clevis end and probably the extension tube itself, to made of something more substantial than 16ga steel. Just visually speaking, I would not want my homemade parts to be any weaker than the store bought parts.

It is rare that I disagree with MV8, but I think the flats are a better solution than the spanner idea. My reasoning is that I've never had a spanner that didn't deform the metal around slightly around the hole while tightening. If the tube extension is CRS it is virtually a given that it will. But neither solution is a "good" on IMO. See below.

Further, I don't like the idea of the spliced area passing laterally thru any form of bushing as the two OD's will virtually never perfectly align to each other. Each time you turn, it will wear/cut the UHMW down. What is your total travel distance? Is it possible to locate the UMHW bushing so that the lateral travel will be totally on the extension tube? That way neither a deformed spannerhole, a flat, or a misalignment of the rods are an issue.

While pretty, I'd also reconsider simply welding what appears to be a flat washer to the end of the pipe and dropping a bolt thru the tube to secure it to the rack. If that is how it is, then you are relying on a ~1/16" weld for your steering. I would rather see a bung welded inside the tube and tapping a hole. Then use a Grade 5 or 8 threaded rod to connect the two tapped holes together. Possibly plug welding the thread into the extension tube's bung.

BTW, the rest of your fab work is top notch IMO.

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PostPosted: February 25, 2019, 11:58 am 
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Dave, supports like you describe were to be added using uhmw plastic.

Good point Chuck. I didn’t say it, but solid bar in the tube as shown on the drawing was a given.

John, why didn’t you copy my design from the roller chain steering topic as-is?
viewtopic.php?f=53&t=19690&p=245758&hilit=rack#p245758
All you need is the one split bush and all the other issues are eliminated.

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