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Learning how to build Lotus Seven replicas...together!
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PostPosted: October 23, 2015, 5:05 pm 
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Oh god. I'm going to have to be careful with my flippant think-tank spitball bounce-a-round ideas...
One of you might just decide to take one and run with it. :shock:

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PostPosted: October 23, 2015, 10:23 pm 
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Back in 2011 I sketched out an arrangement that used a front roll hoop for a windshield frame and dispensed with the usual scuttle. I recently found out that had been done years before with the Sylva Striker.

The Striker windshield seems to be nearly rectangular; I'd probably shape it more like a conventional Locost. The hood comes up against the panel below the windshield. Some cars had a flat dash, some had a molded fiberglass dash. Some had a conventional windshield, others had a short hoop, some had a long hoop going down to the bottom of the frame, some had a conventional windshield with an external hoop bolted to the sides... well, it's a British kit car, after all...

The "rail buggy standard" 1-1/2" front hoop is so common that they make a windshield gasket specifically for it, to take laminated safety glass.

The Sylva's pyramid shaped sides are a lot simpler than most of my sketches.


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PostPosted: October 23, 2015, 11:28 pm 
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TRX wrote:
Back in 2011 I sketched out an arrangement that used a front roll hoop for a windshield frame and dispensed with the usual scuttle. I recently found out that had been done years before with the Sylva Striker.

The Striker windshield seems to be nearly rectangular; I'd probably shape it more like a conventional Locost.



Surface mount windshield like all the modern cars are doing it. Then the shape of the roll bar behind the windshield isn't as critical and any twisting of the frame, like say in an Off, won't crack the windshield.

The new windshields all come with black paint around the edges so that you don't see the glue or structure underneath.

It's also better for airflow & water flow as it doesn't build up (and/or leak) around the edges.

Simpler is better.

You could even build a small fiberglass form to bridge the gap between the shape of the windshield and the roll bar (or push it forwards for better vision or a more laid down angle) if you needed to so that you could retro fit this to your finished car.

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PostPosted: October 24, 2015, 11:27 am 
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Continuing from the lengthy suspension design message the forum ate last night, I found out why I had trouble finding 14x1.5 jam nuts. Indeed, jam nuts in any size. For some reason the common trade name seems to have changed to "half nuts." To me a half nut is a specific type of nut normally found in a lathe.

The going price seems to run about $2.75-$3 each depending on shipping. And I need a dozen of them. Screw that; I have half a coffee can of GM G-body lug nuts, size 14x1.5mm, that will only take a few minutes each to thin down on the lathe. Which will also get rid of the collection of lug nuts I haven't gotten around to throwing out...


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PostPosted: October 24, 2015, 12:35 pm 
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Half nuts from McMaster and Carr

http://www.mcmaster.com/#hex-nuts/=zi9wgp

Less than $7 for 25

John


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PostPosted: October 24, 2015, 12:45 pm 
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Aren't we all half nuts for building our own cars?
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PostPosted: October 24, 2015, 12:50 pm 
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turbo_bird wrote:
Aren't we all half nuts for building our own cars?
Kristian
:thmbsup:

K "Cuckoo for CoCo Puffs" S

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PostPosted: October 24, 2015, 2:20 pm 
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johnzracer wrote:
Less than $7 for 25


Not after shipping. And then I have 15 unwanted oddball nuts I can throw in the coffee can with the random lug nuts.

Looks like McMaster calls them "thin nuts."

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PostPosted: October 27, 2015, 9:09 am 
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Yesterday's rabbit hole was "throttle cables." I never did find any design guides, but I found several places selling automotive throttle cables for buggies and mid-engine kit cars that were ten to twelve feet long, so I decided it's probably not a problem.

This morning's quest was for brake line mounting clips. The Brit guys seem to favor lots of nylon P-clips closely spaced, riveted to the chassis. I have no problem with riveting the brake line, but I've had nylon clips turn hard and break when holding wiring harnesses. Some didn't. I've also had a couple of nylon oil pressure lines turn hard and crackly, twice break while driving; I only use AN-3 lines for oil pressure gauges now. ("There's no kill like an overkill.")

Some of the "nylon" clips I've used are three decades old and going strong. They're usually black with a slick, soapy finish; that's a characteristic of PVC plastic. Online vendors seem to interchange "PVC", "nylon", and "rubber" freely in descriptions, so I've set that aside for the moment.

The rubber-lined Adel clamps are popular with racers. I've had some bad experiences with milsurp clamps; the rubber liners disintegrated and the inside metal edges turned out to be sharp. I caught it before major damage was done, but I've been leery of them ever since. Tens of thousands of people have likely never had a problem with that sort of clamp.

I found some blingy "billet aluminum" brake line clamps. Pretty, pretty... the voices started muttering about galvanic corrosion. Spoilsports.

I noticed that Detroit prefers springy P-clips that lift the line away from the mounting surface and pinch it tightly; the clip is usually screwed or bolted to the chassis. I found replacement clips, same as the ones my Malibu uses, for a bit over a dollar each to my door. Why GM found it necessary to use a 5/16" bolt to anchor a brake line is a mystery to me, but a washer under the rivet head should work OK.

Detroit has used some very fancy spring-loaded clips to anchor brake lines, apparently designed to let them float a bit in relation to the chassis, and often doubling up as fuel and vapor return lines. They're bulky and not really appropriate for my application, but they were interesting.

Most live axles have one flex hose to the axle and one or two steel lines running to the wheel cylinders or calipers. Of all the cars I can remember seeing, the steel lines were universally held by welded J-clips. I don't know if they were welded on and bent over the line, or welded over the line. You have to bend them away from the axle to replace the line.

The springy, bolt-on clips let you hold the line tightly. The welded-on clips... I guess the OEMs don't want bolt holes in the axle tubes, and they figure the lines are held tightly enough. Which led me off down another tangent - all of the spring clips I've found are made to hold the brake lines against a flat surface. The De Dion tube is round; the rivet would only hold the clip on a tangent, and any motion would put a bending load across the rivet head. Rivets aren't made for bending loads, though the load would be quite small. If I use the springy clips on the tube I'll need to reshape the mounting tabs a bit so they curve to match the mounting surface.

My Malibu is 35 years old and the brake line clips are still working just fine. Replacement 10-packs are reasonably priced; for now, that looks like the optimal solution.


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PostPosted: October 27, 2015, 9:42 am 
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TRX wrote:
My Malibu is 35 years old and the brake line clips are still working just fine. Replacement 10-packs are reasonably priced; for now, that looks like the optimal solution.
Hey TRX...

Trying to picture these. Got any visual helpers?

In the commercial kitchen industry (among others), harness and tubing get held with pop-thru and/or sticky back zip-tie mounts. Everyone knows the sticky back. Here's the pops...

ImageImageImage

They're used in current auto applications and get brittle only after years of road exposure (got 150k on mine before they started to show age).

Despite the accessibility and mentality that goes with a Locost though, I don't know that I'd trust either of them to a brake line or other vibration/movement prone application, so I'm really curious as to what your describing.

FWIW - I know they are used a lot, but you hit it right with Adel Clips. They have always worried me for use in "clamping" automotive applications. Even my brother who is an airframer in the Navy shys away from them in auto use!

K "zippy" S

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PostPosted: October 27, 2015, 9:58 am 
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The front of the cockpit: hanging pedals, fuel tank immediately ahead of the cockpit, GM center-steer rack just above the tank and ahead of the pedal pivots. The output shaft of the rack points more or less straight toward the steering wheel. The steering column will be rather short, running from my feet to wherever I decide the wheel will be. All the bits interlock quite nicely.

Nowadays it's quite common to use a collapsible steering column. It turns out there are two different purposes for that. The original 1968 DOT spec was to prevent rearward displacement of the column if the front end collapsed during an impact. I've seen the results of that sort of thing in junkyards.

Designers used various solutions - angled joints, sliding couplers, slit or perforated tubular steering shafts, etc. You can buy aftermarket shafts aimed at the race car market.

There are various OEMs who mount the rack on the firewall, where displacement in a wreck would probably be small. Even so, they sometimes have elaborate collapsing structures in the steering shaft, even though it might be less than two feet long.

It turns out that there's a later spec that requires the steering to be "energy absorbing." This is accomplished by controlled deformation of the steering wheel and by controlling the collapse of the column to take up the impact of an unbelted occupant.

There will only be a hand's-breadth of room between the steering coupler and the scuttle face, so any collapsing bits would have to be moved back over my knees.

Hmm. I'm probably just going to run a short straight shaft and be done with it. The forward structure will be fairly stout, and the fuel tank would have to be crushed before the rack could be displaced much.


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PostPosted: October 27, 2015, 10:07 am 
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botbasher wrote:
Trying to picture these. Got any visual helpers?


Sure. They're quite simple. GM uses a bolt, which is why the holes are so large. When bolted (or riveted...) there's compression of the line so it can't move and fret against the clamp.
Attachment:
brake clip 1.jpg
brake clip 1.jpg [ 9.9 KiB | Viewed 1849 times ]


EDIT: I just remembered what those remind me of; the "Fahnestock clips" in the "1001 Electrical Experiments" toy I had when I was a kid. Well, it *has* been nearly fifty years since I've seen one...

EDIT 2: *AND* I remembered how to spell "Fahnestock", according to Google anyway. I'm going to count that as a double win.

Quote:
I don't know that I'd trust either of them to a brake line or other vibration/movement prone application,


Same here, but it looks like they'd be handy for holding wiring bundles. I wouldn't want to push them through into a closed tube, though. Maybe a mounting tab; they don't look watertight.


Last edited by TRX on October 28, 2015, 12:21 am, edited 2 times in total.

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PostPosted: October 27, 2015, 10:15 am 
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TRX wrote:
Same here, but it looks like they'd be handy for holding wiring bundles. I wouldn't want to push them through into a closed tube, though. Maybe a mounting tab; they don't look watertight.
I'm planning on a dab of silicone under each one. Do the same on rivets too. That should keep anything unwanted out of the tubes.

K "Sillycone" S

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Never become a pessimist. A pessimist is correct oftener than an optimist, but an optimist has more fun, and neither can stop the march of events.-Robert A. Heinlein


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PostPosted: October 28, 2015, 12:16 am 
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I had to go by the steelyard today, so while I was there I had them order a stick of 3" diameter, .063 wall round steel tube. That will be the De Dion tube. Hopefully I won't crush it while bending it or warp it while welding it... They don't normally stock that size, so it won't come in until they make another order from their upstream supplier. I wasn't in any hurry so there was no need to pay for special shipping.

I also finished welding up the press fixture to get the axles out of the Geo hubs. The service manual recommends using a slide hammer while they're bolted to the car, which would be fine, except these are laying on the floor where I trip over them. As usual I now have a rather elaborate tool that I may only use a few times, and then it can sit in the bottom of one of the toolboxes. At least I've learned to use a felt tip to write their purpose on them so I don't forget what they're intended for.

Meanwhile I'm working up the shopping list for the rest of the steel; pipe for the ball joint mounting rings, tubes for the steering shaft, steering column, bushing housings, A-arms, trailing arms, tube for the chassis, etc.


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PostPosted: November 2, 2015, 8:49 am 
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More on the brake line clips - the mounting holes look to be much larger than a 1/8" rivet, and I probably don't want to be riveting the brake lines into areas I can't get to to drill the rivets out if I need to...

I just went through a bunch of pages on rivnuts and nutserts. It looks like what I need is "keyed rivnuts", which are rivnuts that have a lug on them that is supposed to prevent them from spinning if the bolt galls or corrodes. Of course they seem to be rare, but Aircraft Spruce has them, and at a reasonable price, too.

Part of the rivnut sticks up, unless you go for the countersunk rivnuts. The stick-up part looks perfect for locating the brake clips. I need to order the clips first to measure the holes to match them to appropriate rivnuts.

There are, of course, special tools for installing rivnuts. I found a couple of pages on doing it with some scrap metal and elbow grease. Since I only need a dozen or so, it will be hard to justify the tool.

---

The press fixture worked perfectly to disassembly the Geo knuckle. If it ever stops raining I'll slog out to the shed shere the other knuckle is stored and press that one out. Getting the bearings out required sliding the spacer sleeve over and tapping them out of the knuckle with a steel bar. Since the bearings were very tight I had to turn "tapping" up to "I wonder how much force it takes to damage the balls and races, anyway?" There's just barely enough of the outer race visible to make a tool and drive the second bearing out with the outer race, but the first bearing... I might try to come up with some sort of bearing puller arrangement. It would still put the removal load across the balls, but at least it wouldn't be hammering on them...

Maybe I'm overthinking things, but I've destroyed my share of ball bearings in my time. (Japanese motorcycle wheel and headstock bearings used to be made out of chicken-wire-grade steel...)

I replaced the right front wheel bearing in my Metro six or seven years ago; it was two balls and a spacer. Apparently the later cars went to a considerably more expensive single, double-row bearing. The hubs I got from BobM are the older style like mine. Which suits me fine; the bearings are $50/pair instead of $80/each. These look fine, though, absent any dents from my hammering.

---

Interestingly, the Geo axle flange is *not* hub-centric. The wheel is locating by four cute little 10mm studs and the face of the drive flange is flat. I have no problem with lug-centric wheels, except when the wheels use shank nuts, where the nuts need clearance to turn.

Since it's a drive flange the axle goes all the way through, with a washer and a nut. Plan A is to make some new, larger washers to locate the wheel, counterbored for the nuts, with clearance for a socket.

Somehow, I find it amusing that I'm using Honda rear hubs in front, and Geo front hubs in the back...


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