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Learning how to build Lotus Seven replicas...together!
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 Post subject: Re: Exo Hot Rod
PostPosted: August 19, 2018, 12:25 pm 
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Hi 'Graveyard' - I think it's sad when these logs come to a halt, instead of an end, and without explanation... but quite tragic with such a beautiful build as this one. I sympathise with whatever problems you've had and hope, more for your sake than mine, that you will be able to pick it up again some day...
Good luck, MangPong.


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 Post subject: Re: Exo Hot Rod
PostPosted: February 16, 2019, 6:28 pm 
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Long time, no post. Life got in the way, though not in a bad way; had another kid (number four), bought a house, and lots of smaller things.

I no longer had time to post anything, but I did not stop building. Since my time was limited, I put what time I had into actual working.

Today, I'm nursing a cold and it's 10 degrees outside, so I though I'd just get a start updating.

Three big things have happened:

1) The big news! I started over. Lots of reasons, but the thing that tipped the balance toward a do-over was wanting to do some drag racing with this car someday. I needed thicker-walled, DOM tubing to meet the NHRA specs.

2) I built a jig. Not a general build table, but a very rigid, very heavy jig for this specific build. It positions everything perfectly, and gives me peace of mind that everything is square.

3) I bought a tig welder (AHP, which I like), and everything in this second version is being welded with tig.

I'll start adding some pictures now, as they'll tell the story pretty well, I think.

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 Post subject: Re: Exo Hot Rod
PostPosted: February 16, 2019, 6:59 pm 
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There was a local place selling scrap steel dirt cheap. Lots of random pieces in random shapes and sizes, plus super heavy angle that was even cheaper. Every piece of angle was $5, regardless of size, so I picked up several pieces of 6-8' x 5" x 3/8". Yep, all of those square tubes you see in the pictures are made from paired angle pieces welded at intervals along the seams. The long square tube is actually made up of four pieces. That one was tough to get right; after welding it together I had to straighten it a bit by strategically stick welding.

Welding the newly made square tubes together to get them into a flat plane was challenging. The goal was to get a little closer to dead on with every piece I added.

Then I used other extremely heavy bits and plates to hit the exact spots where the frame should hit the subframes, per GM's specs.

In two of the pictures below I show sections of the C5 Corvette frame rails bolted in place, just to illustrate what this jig does.

Jig pictures:
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 Post subject: Re: Exo Hot Rod
PostPosted: February 16, 2019, 7:23 pm 
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After I started over, in my new garage (30% bigger, but not particularly nice), with my new jig, I did some things differently.

First of all, I built the spools differently. The spools are the 8 points where my tube frame will bolt to the factory subframes. I decided I wanted pieces that were more robust, so I upgraded the compression tubes to 1/8" wall, the end plates were thickened to 3/8". Additionally, I drilled out the bottom plates to 3/4" to match the inside diameter of the compression tubes, then fully welded the compression tubes to the bottom plates before sliding them into the outside 1.75" tubes. The top plates were drilled to 1", fitted over the tops of the compression tubes, and then everything was fully welded. Very, very strong.

After I had the new spools done, I added the connecting tubes and the suspension bracket mount tubes, the front and rear hoops, then the inner and outer floor tubes.

The pictures are from my test fitting on the drivetrain. This was the first time and only time I've had it off the jig.

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 Post subject: Re: Exo Hot Rod
PostPosted: February 16, 2019, 8:02 pm 
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Okay. That brings us to some pretty current pictures. Not because I didn't get much further, but because I took almost no pictures again until recently.

There were a bunch of things I adjusted or changed significantly, so I'll try to mention some of the big ones, but there's no way I'll catch everything.

1) The roll hoop is 3-4" further back, I did this to improve foot room and the overall shape of the car.

2) The cowl and front hoop are both significantly lower, to improve forward visibility.

3) The cowl is several inches further back, for aesthetic reasons, mostly, though it certainly moves the CG back a little. This was, again, something I drafted first, in several versions.

4) The main hoop is wider at the top, and at the sides. 3" at the top (I think), and maybe 5" on the sides. This is for the look of the car from the front, and for head room.

5) The cowl is 4" wider, to match the main hoop, and also match the floor better.

6) I was able to simplify a lot of the very complicated tubing junctions, partly because I made my spools a lot taller, and partly because I'm a little smarter the second time around.

7) The whole rear suspension-mount area is completely different. A stronger and more elegant design.

In these pictures the butt of the car is jacked up an extra foot to make my welding work a little more comfortable.

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 Post subject: Re: Exo Hot Rod
PostPosted: February 17, 2019, 12:49 pm 
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That frame looks amazing! Glad to see some updates! I recently picked up an AHP AlphaTig, but I'm currently working on actually adding the necessary power to use it in my shop. Do you like yours? I've never done Tig before but I'm hoping to teach myself.

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 Post subject: Re: Exo Hot Rod
PostPosted: February 17, 2019, 3:18 pm 
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I really like the AlphaTig. I run it on 110v (20amp breaker), because that's all I have in my garage at this point. I can tig at 150 amps all day long with no trouble (though I rarely set the machine over 140). It will blow the breaker if I stick weld beyond 100 amps. Don't know why.

Really, 150 amps is a lot for tig welding steel. With appropriate beveling you could weld anything steel. It's really only for thicker aluminum you'd need all 200 amps.

You might consider just plugging the thing in to start practicing. Use a lower amp setting if you don't have a 20 amp breaker. Set the machine at 60 amps and I'll be you can't even blow a breaker, regardless of where you plug it in. 60 amps is about all you need to weld the standard 16 ga. steel most seem to use in locost builds.

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 Post subject: Re: Exo Hot Rod
PostPosted: February 17, 2019, 5:29 pm 
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As I'm still today feeling like rest is a good idea to be recovered for work tomorrow, I'll fill in a little more. First, the alternator bracket:

The stock C5 bracket mounts both the power steering pump and the alternator. The ps pump is tucked in nice and close on the driver's side, but the alternator hangs out over the stock frame rail, which won't work for my application.

In this picture you can see why (this picture is from the first version of the build): The alternator (not there, but you can see where it bolts on) would run into the shock mount tube. But even the bracket itself ends up in the way of the driver's-side shock mount brace that goes from the top of the shock mount to the middle-top of the front hoop.
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Fixing the stock bracket itself was a simple but messy 30 minute job with the angle grinder. I just removed everything but what was required to maintain the structural integrity of the ps bracket. There were two simple alternative locations for the alternator: on the bottom passenger side where the AC compressor usually goes, or in the middle on top. In the long run, would prefer to have the alternator in the AC compressor spot. It brings the weight lower, and also cleans up the most visible part of the engine. There were, however, a few things that pushed me to put it on top for now.
-First, this stock alternator is pretty big and it would have been kind of a tight fit down low. With a small aftermarket (read: expensive) alternator it would work much better, but I have other places to spend my car money right now, and I always like the idea of OEM parts when I can make them work.
-Second, putting it in the AC compressor spot would also mean using the smaller secondary AC belt for the alternator rather than the main serpentine belt. That means using an additional tensioner, and I don't know how well the length of the stock 3-rib AC belt would work. I think it could be made to work, but it's another unknown. How many different lengths of 3-rib serpentine belts are on the market? -Third, having the alternator down low, especially on the passenger side, puts it more or less under the water pump/thermostat housing. It's a prime spot for coolant leaks, and I don't like the idea of coolant in my alternator.
-Fourth (and finally), it would be difficult to get the alternator mounted/dismounted. I think it would be possible, it certainly would be with a small alternator, but it would be a pain.

So, that left a top mount. An alternator wouldn't normally fit up there, but since I'm using a Victor Jr. intake manifold instead of the factory piece there's plenty of room. Got lucky.

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The bracket is actually in three parts, which you might be able to tell from the photos. The main piece is a 1.5" square tube that runs flush with the passenger side head, welded to another 1.5" square tube that's level with the top of the engine and crossing to the driver's side. It has 1/4" steel wings welded to the passenger side piece, drilled for bolts that affix it to the head (3 bolts), and the top tube has an 1/8 angle extension to bolt on to the power steering bracket on the driver's side. The top tube is also fitted with two compression tubes (3/4" x .120 DOM, for 1/2" bolts) spaced to match the factory alternator. They were beveled in, tig welded, and ground flush. Two 'sub-brackets' bolt onto this tube on the bottom, and to the alternator on the top. This will allow me to use this same setup for a smaller aftermarket alternator at a later date, or any alternator I choose, without having to redo the whole thing. It also makes it more easily adjustable for the current alternator, if I don't have it aligned exactly right.

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You can see in the pictures that I don't have the belt going around the ps pump yet. It clears just fine, but I'm using a shorter belt for now because I don't have to have the ps pump attached to the rack right now and I don't want to run the pump dry. I also happened to have a shorter belt that fits perfectly when I skip the ps pump.

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 Post subject: Re: Exo Hot Rod
PostPosted: February 17, 2019, 6:48 pm 
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I think I have one more update in me for today. I tend to feel unproductive when I'm sitting at a computer, but I'm not yet up for going to the cold garage, and these updates are long overdue.

My big ancillary project has been the run stand. I realized this spring that it had been two-and-a-half years since I'd received the C5 stuff, and I hadn't yet run the engine. That was partly because I was itching to get going on the build, and partly because I needed to supply all of the fluids first. It's only about $100-$150 worth of fluids, but I was needing every last bit of budget for building materials. Anyway, seeing that I might easily end up getting beyond three years without running the engine, especially since I restarted the whole project, and feeling the need for some engine sounds, I decided to build a little run stand that would bolt to the drivetrain.

I had bought the Holley 700 cfm DP at a swap meet for $10 at least a year earlier, but hadn't done anything with it. So, I bought a rebuild kit, three bowl screws that were missing, the correct jets, check valves for the squirters, and one new fuel bowl. I guess I needed some fittings for the fuel log as well, so I'm probably into the carb for about $100. Not too bad if it doesn't need anything else.

I already had the MSD box to run the LS ignition.

The VDO gauges, Carter fuel pump, Holley FP regulator, Summit FP gauge, and various wires/relays/switches were leftover from a previous build.

The plastic coolant reservoir is from a 2000 Suburban that I parted out so that I could keep the 5.3 with a matching title (this will be relevant later!).

The radiator is a leftover from a C4 corvette.

I used the factory C5 frame sections to bolt to the front subframe, and then leftover tubing from my first attempt at this build to make the structure. It all bolts on and comes apart in pieces.

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I keep it sitting in the garage covered in plastic, but on HF furniture dollies, so I can push it out into the driveway, hook up my fuel cell and a battery, and run it. At least that was the idea. I finished the whole thing the week of Thanksgiving, but it hasn't run yet. I have spun the engine with the starter to look at the oil pressure (GREAT oil pressure), but that's it.

I have tried twice, because since Thanksgiving we have had only 2 reasonably nice days when I have had time to do anything with it, and failed for a different reason each time.

The first time, the carburetor became a fuel fountain as soon as a started filling the bowls. It poured so much fuel into the engine that I had to pull the plugs and spin it with the starter a bunch to squirt/blow out the fuel. And, of course, that day the rain clouds were coming just as the engine was getting filled with fuel, and the weather wasn't nice again for more than a month.

In the meantime, I sorted out the carb issue. I had made a stupid mistake assembling the carb, of course, and put the primary float damper spring on the wrong way so that it was pushing the float down into the fuel rather than lifting it, so the needle never shut and I had quarts of fuel filling my engine (which I didn't know right away because the air filter was on, another mistake). That was an easy fix.

My second try was the first week in January, when it was again very nice (over 45 degrees, and not raining), and I, having solved the carb issue, was ready to give it another go. I took the 15 minutes to set things up in the driveway, and pushed the starter button to turn it over for a few seconds and get oil pressure (which I had done several times already, both checking oil pressure and voiding fuel), but the engine only made a partial turn before making a bad noise and no longer turning. Additional tries resulted in the same. I had 40 minutes to see if I could solve the problem, before I would have to start getting everything back into the garage, but I couldn't find anything wrong and the rain was coming.

I got into it a little more then next day, and found the problem:
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That's right, the ear is broken off the starter. Suddenly. I know that this is a weak point for some early LS1 starters, but I can't imagine why it broke when it did. It must have been nearly-failed for a long time. I just happened to have parted out a 2000 Suburban, and had the starter, which not only fits, but also has that weak point fixed. I can't imagine why GM would put a stronger version on the smaller-displacement, lower-compression 5.3 of the same model year. Maybe the starter from the Suburban was a replacement, the original having broken years ago. I don't know. But, I had a replacement starter on hand and installed it. I was lucky that the broken ear on the starter did not break or crack my aluminum LS1 block. Sometimes they do that, I've heard.

I don't know when I'll have another nice day to try again running the engine, but it doesn't look like it will be this month. I will say that I'm more mentally prepared for something to go wrong next time. Kind of expecting it, actually.

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 Post subject: Re: Exo Hot Rod
PostPosted: February 17, 2019, 8:22 pm 
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Omaha Vette Graveyard wrote:
I don't know when I'll have another nice day to try again running the engine, but it doesn't look like it will be this month. I will say that I'm more mentally prepared for something to go wrong next time. Kind of expecting it, actually.


If you had a TV show there would be "drama music" and "drama drums" when things went wrong. Then of course a commercial break?

If this was easy, everyone would do it. And if I could work metal as good as you, I'd switch careers...

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 Post subject: Re: Exo Hot Rod
PostPosted: February 17, 2019, 11:08 pm 
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 Post subject: Re: Exo Hot Rod
PostPosted: February 18, 2019, 8:37 am 
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Yo-
With the kind of luck you're having... Would you like to be an honorary* member of Team Slotus?

*Some would call it a "dubious honor"... I'm not sure it's even that good... :mrgreen:

Regardless of the outcome of the engine tests, you get an A+ for having your helper out there with you.

Keep after it, you'll get there.
:cheers:
JDK

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 Post subject: Re: Exo Hot Rod
PostPosted: February 20, 2019, 4:02 pm 
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Kind words, everyone. Thanks.

The requested dimensions of the C5 trans/diff are:

Front fat part (where it bolts to the torque tube): 13" wide x 14" tall

Front mounting flange (again, where it bolts to the torque tube) to the axle centerline: 23.625"

Getting those measurements is the only time I've been out to the garage in the last week! Terrible!

I won't get out today, but I think I'll be able to get out just a bit tomorrow.

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 Post subject: Re: Exo Hot Rod
PostPosted: February 24, 2019, 3:57 pm 
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Had another productive day yesterday, and I think the back of the car (behind the main hoop) now has all of its tubes.

This configuration of triangulating things was a little trick to figure out because I'm trying to do a few things at the same time.

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First of all, I'm trying to connect the main nodes. Second, I'm trying here to create flat-ish planes on each side so that the aluminum panels will be fairly simple to fit and bolt on. In the back, I'm primarily concerned with paneling the two boxes behind the seats. The passenger side will have a fuel tank inside, with the battery behind the driver. The middle triangle area is, perhaps, the window through which I'm going to suck air from the bottom of the car to feed the radiator. Haven't decided that yet. Might require some testing/development to get that sorted.

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I also finished the X brace between the top rear suspension mounts.

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You can kind of see the other gusset tubes I added that brace the rear suspension mounts and the spools.

There is one more set of tubes I'm thinking I probably need to add; the kickers for the cage. They'll go from the main hoop just under the harness bar, down 'through' the cross bracing tubes, and hit the tunnel. They'd not be worth much for this chassis, but my reading of the NHRA cage rules tells me that I have to have them. I'd love to hear that I'm wrong about that.

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 Post subject: Re: Exo Hot Rod
PostPosted: March 6, 2019, 2:35 pm 
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Though I'm working on the seat bracket mounting tubes (will explain the terminology in a later post), Jegs has had a hard time getting me the crush/compression tubes I need to finish. So, in the meantime, I finished the A pillar support tubes.

I elected to use some of my remaining heavy tubing for this spot. The reasons are: 1) Some would consider these tubes part of the cage. 2) Being part of the cage they need to be of some cage-spec tubing, which means either .083 4130 or .120 DOM. 3) I had some leftover pieces of .120 DOM in suitable lengths. 4) These tubes effectively double the amount of steel connecting the roof of the car to the front firewall.

Having not done any kind of FEA or specific testing it's only a guess, but I think a reasonable one, that the top side of the passenger compartment, the roof area, is the weak area in this car, given it's the only side of any of the boxes that is not triangulated in-plane. And, where I'll have no bonded-in windshield to help structurally tie the roof of the car to the cowl, I need to get a lot out of the A pillar/support tubes. So, I'm essentially guessing that using large-diameter, thick-walled (heavy) tubing in this particular spot will make a significant difference in the overall torsional stiffness of the vehicle. I'll save the 4130 for the roof and back triangulation pieces which are loaded almost entirely in tension and compression.

I'm prioritizing strength and stiffness over lightness in my choice of tubing for this car. The nature of the build, being an exo, will make it comparatively light, but the Corvette drivetrain and running gear alone probably weigh in excess of 1200 pounds, so this isn't going to be a 1500-pound car. Probably up closer to 2000 pounds. If I could have a stripped-down autocross version at 1800-1900 lbs. I'd be pretty pleased. For drag racing I might end up with a twin-turbo or nitrous package that puts down power north of 1000 hp, so I kind of like the idea of overdoing the chassis a little.

Pics of the process:

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File comment: Finding the right angle for the right look, and right dash position.
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IMG_20190303_194734040.jpg [ 665.87 KiB | Viewed 1025 times ]


Attachment:
File comment: Jigged up for tacking
IMG_20190305_132932767.jpg
IMG_20190305_132932767.jpg [ 915.66 KiB | Viewed 1025 times ]


Attachment:
File comment: Tacked in
IMG_20190305_134427589.jpg
IMG_20190305_134427589.jpg [ 753.23 KiB | Viewed 1025 times ]


Hopefully I can get the floor tubes done with some pics for my next update.

_________________
Aedifico ergo sum.


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