Sparks are flying again...

It’s been a long time since I spent any meaningful time working on the Locost. My career has taken a couple leaps since I began the project and time has been extremely scarce. I currently have a little break until things will ramp back up at work. I’m a low-voltage cabling guy who has worked a variety of positions in the industry over the past 14 years. Two years ago I was briefly out of work before being picked up by a small company in Milwaukee who had a big customer in Green Bay and needed someone to manage a multi-year construction project. I almost fell over when they told me I would be working at Lambeau Field (Green Bay Packers)!

The construction projects and renovations are roughly half the battle; we also do no small amount of work directly for the team. When I started we did the usual voice/ data, fiber optic, wi-fi, and similar system cabling projects. Since then we have added cellular and emergency DAS systems along assuming responsibility for the broadcast system. I have additionally been named the Media Liaison and serve as a point man between the team and media partners. This role includes me and a few of my key folks working on game day media preparations and working directly on the sidelines during the games. When you see guys dressed all in blue during the games think of me… and the fact that a locost is not being worked on at all that weekend!

With the increase in work and the long term prospects of my new role my house is also up for sale. Buying a place with some serious garage space is high on the priority list… just not sure how long it will take to sell the house. It’s now been for sale 2 months.

We currently have a little lull between projects, so I’ve been able to make some progress. I’ve added the rear round tubes to the chassis, made the differential and transmission mounts, and have shortened the stock Miata driveshaft. 

Shortening a driveshaft involves some risk; I decided I would order a custom driveshaft once the car is complete but wanted something I could use for fitment and low-speed testing. If and when I ever finish the car I will then sink the money into a custom driveshaft. My stocker has 189,000 miles on it and the u-joints are non-replaceable, so I didn’t see much point in paying a pro to shorten something that should probably be replaced anyway.

I started by taking a flapper disk to the driveshaft to strip the paint and surface rust off. I then wrapped a sheet of paper around it until it lined up and tape it in place. I used electrical tape (white was at hand) and wrapped it carefully around just short of the paper edge. After measuring 11.75" I repeated the process and then used a handheld bandsaw to cut closely to the tape edges. A bench top grinder was used to bring things right to the edge of the tape and bevel the edges for a cleaner weld.

Prior to cutting it's a good idea to lay a piece of angle iron along the shaft and scribe it with a straight reference line. Pay close attention to the orientation of the yokes on each end prior to cutting: you must keep these in the same alignment with each other or your universal joints will become universal binds!

For the next trick take a piece of angle iron and strap your drive shaft pieces into it so that your reference lines line up. If you're like me you can be in a hurry and forget about the reference lines for now. You'll have time later on after welding to remember why the reference line was there and you'll get twice the experience cutting the shaft and doing all this again (don't ask).

After tack welding the shaft in 4 places I laid a weld bead around the circumference and carefully ground it smooth. 

The transmission and diff mounts are pretty basic and only need to give me a decent surface to mount to. I used 1/8” plate 4” wide and spanned some of the chassis structure. My motor retains the stock rubber mounts, so I also needed to use rubber mounts on the tranny and diff. In the locost spirit I used a hole saw to cut up a 1/2” rubber mat and then drilled the holes out a little larger. I have enough mat left over I could do my suspension arm bushings with the same material. I haven’t decided whether I want to go that low-cost yet. The extra money for polyurethane bushings would be well spent in the suspension.

You can see in the following picture the diff mount is pretty simple and will allow me to bolt the nose in place with rubber fusions above and below the diff. Looking forward in the tunnel the same idea is used to hold down the transmission. I am mounting the transmission from the old power plant frame bolt location versus using the less robust location near the tail shaft.

Bending the round tubes in the rear was accomplished with far too much thought and consideration of all the options. I decided to quit being a wuss and fabricated a rough jig on my build table. I welded the end of a 3/4” round tube shut, filled it with dry play sand, tapped and packed the sand in until full, and then welded the other end shut. I heated the area to be bent with a torch until really hot and then bent it around the jig. The results are certainly workable. In the process of making bends and cuts I made enough mistakes to make any professional cringe, but owning a welder and grinder allows one to cover a multitude of mistakes. I’m getting really good at welding sections of 3/4” round tubing back together and keeping the results straight. 

If you bend the ends of the tube and end up with a twisted tube or the wrong length it is easily repaired...

The jig for bending is simple enough. I used a piece of oak board and cut out a 1.5" and 2.5" hole. The holes in the center were then drilled out out a little so I could put a 2" long 3/8" lag bolt through it, the MDF build table, and the 2x6 support. By grabbing the pipe on the right I was able to bend the pipe around the radius of the cut out.

The book drawings show the top hoop is bend on a 3" radius while the bottom corners are bent on 2" radii. My bends are little tighter than what the book calls for due to it being late while I did this. Radius, diameter... whatever. If you are following this build log with plans to build your own car I'd suggest cutting out 2.5" and 4.5" diameter holes. Then mount your backer board more firmly than mine (mine has a single pivot point and moves some). You will then force the tube to follow your radius more closely. I think mine are right on the money though it took a lot of sheer dumb luck- something I seem to have (and require) an abundance of.

I’ve only got a handful of tubes to weld in to complete the chassis complete with redesigned rear end for a Miata IRS suspension. My self proclaimed goal for this year is to finish the suspension and get this thing on its wheels. If I have steering done as well I’ll be very happy. We have some huge projects on the horizon at work so things could get crazy again soon. 

Frame construction

 

After spending a bit of time looking at the motor mounts I decided I didn't like the peaks sticking up, so I cut them off level and capped them while adding the mounting plates. There is no question these will support the engine.

 

I've also added diagonal bracing- the following picture only shows the front additional tubes. I later realized I went the opposite direction with them than most people though the end result will be the same as far as stiffening the frame. The tubes are actually pulled in a little closer to the engine this way but I will still have plenty of clearance with the engine, exhaust, and steering components, so I'll leave them this way for now.

Here's another picture of the bracing.

And I'm now beginning construction on the rear end. Because I'm using a Miata donor I'm designing in an independent rear suspension. This is a tubular version of the Miata subframe and is actually quite easy to build... after spending way too long plugging it into LibreCAD. I really hope it works!

Finally a warm evening to work!

Last night was the first warm evening we've had since last Fall and I was able to spend the entire evening in the garage working on moving some tubes around and making the engine mounts. I've decided to keep the engine offset 1/2" to the passenger's side and lower the engine 1.5 to 2"  below the bottom of the frame. This helps me avoid reconfiguring the top cross tube behind the engine and should help the hood clear the top of the engine more easily.

I decided to make triangular mounts partially because they'll look cool, should easily be strong enough, and allow access to the engine mount bolts if I avoid closing the bottom of the chassis in between the supports. I use 16ga 3/4" square tubing and am considering cutting the top peak off and welding the holes closed. I have yet to add 1/8" sheet to the insides of the mounts.

Recent Progress

More tubes have now been tacked in though progress is a little slower than I hoped due to weather being usually cool. Once it warms up a bit I'll be spending a lot more time in the garage. Here you can see the engine and transmission sitting roughly in place. I think I'll need to lower the engine another inch, move some tubes around a bit, and then fabricate the engine mounts.

The engine is spaced 1/2" to the passenger's side due to the rear differential being offset 1" to the same side. I'm hoping to minimize the drive shaft angle: a little angle is beneficial for keeping the U-joints properly lubed, but too much causes stress.

The design work and planning gets a lot easier when you can use a CAD program. Luckily my previous job taught me how to use AutoCAD. Unfortunately I do not have my own copy, so I had to take a little time to learn LibreCAD which is an open source free CAD program.

Here I mocked up the rear end borrowing some ideas from Matt Rodger's car as detailed on the LocostUSA forum. I also took some measurements on the current transmission output shaft and differential input shaft. Once I get the engine and transmission mounts completed (and moving tubes around a little) I'll be working on the back end of the car. At least the cool weather gave me a chance to iron out some ideas and develop some plans!

Taking shape

The past week was spent tack welding the tubes in place and adding more tubes. I was a little worried about front trapezoid as it requires compound angles to cut, but it turned out well. The top tube is three inches behind the bottom tube.

 

 The build table is 42" wide by 96" long. A nose cone will fit over the front trapezoid and the high angles rear portion is the back of the seating compartment. The back of the chassis will be extended for the rear differential and suspension.

 

 A shot from the front to illustrate how parallel the cross tubes are. If you make a mistake on the basic chassis it will haunt you for the rest of the build by effecting all the measurements afterward and the quality of the finished product.

The car is beginning to take shape although my oldest son thinks it looks like a boat right now. Haha!

After a lengthy break progress resumes...

Since March of last year I have been terribly occupied with repairs and upgrades to my house, repairing daily driven vehicles, and working my tail off at my new job; I install communications cabling at Lambeau Field and there's a lot of work in progress! Work is good. It covers the costs of my hobbies including building a locost. In addition to work selling the Cherokee and Miata (for nice profits) also has helped.

I've now taken the plunge and purchased much of the steel I will need for the basic frame. I've also covered most if not all of the tooling which is required to do something like this. I did have some time and money last summer to construct the build table out of carefully selected 2x6s and a sheet of 5/8" MDF. I used metal bracketing to add some strength and casters for mobility. Luckily I've found a place in the garage which is very level so shimming is unnecessary.

I've begun cutting the frames for the bottom portion of the chassis. I am building this to the "book chassis" dimensions.

A cheap miter saw with a 10" abrasive blade allows me to cut angles with a high degree of accuracy. The bench grinder and a bastard file allows me to dress the tubing ends quickly before laying them on the table. The miter saw was purchased on sale for roughly $70 and the abrasive blade costs roughly $5.  I laid a 2x2 along the edge of the build table to hold the steel even while cutting. As an extra benefit: the 2x2 keeps the tube I'm cutting from moving the pieces around on the build table. The saw/grinder stand is on casters so it can be quickly repositioned as needed.

This is what I mean by "a high degree of accuracy". So far all the joints look like this.

I wanted to test the settings on the welder and pieced some scraps together... the resulting gun-shaped creation delayed getting any work done until I finished (hardly) amusing my wife and kids with James bond impersonations.

After spending years trying to get all the tools and skills together to begin the actual construction I am greatly pleased seeing it underway! More to come soon!

Cutting down the steering rack

Here are some pictures of cutting 5.5" off the Miata steering rack and welding the parts back together. This is not the preferred way to to shorten a rack, but it is the cheapest. The quality of the welding is vital to say the least!

These are the shortened pieces:

These are the parts that were removed- I used a cheap compound miter saw with a 10" abrasive blade:

Here is the assembled rack. Part alignment was handled by strapping the parts to angle iron while welding and the end result was pretty good. Everything is straight!