LocostUSA.com

Thanks for the encouragement. Got the back wall of the shop cleared out (that only took 5 hours!) and put a work bench there for the lathe. I need to beef it up a little to support the weight, and then see if the ground is dry enough to safely get my 2WD truck in and out without getting stuck. I hope so, 'cause we've got another 2 days of rain coming, and I hate having the thing sitting in the truck under tarps in the rain. Maybe I'll go buy gravel instead.

As for building my own engine...HAH! Maybe a little model steam engine some day when I get bored/boring, but a V8 is WAY out of my league. To be honest, I'm still not sure what I'm going to do with the lathe. The tie rod extensions where JR's idea (GENIUS!), and I really don't know what my next project will be. I gotta start looking for round problems needing solving.

If you guys need something built, drop me a note...I'm eager to tackle more jobs.

JR - Glad to hear they work for you. Do you know if you'll end up cutting them down any?

-dave

_________________
...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]

Steam engines are way cool. Don't get me started. I'm starting to picture a seven with a vertical stack.

But so far as the motor goes, gives one a better appreciation of those two home build guys who said "hey that's a nice bicycle, let's invent aerodynamics now, then design and build internal combustion engines on the side. Look we can use those files!"

What a jaw dropping project to actually carry off. Then again maybe their family were called Wrights for a reason... ( wright means a builder doesn't it? )

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.

Six more hours, and the 10x22 lathe is in place and under power!

It took me and a friend a total of about 6 hours to get it out of the truck into the garage, reinforce a wooden work bench, get 800 pounds of iron onto said bench, and tap a new 220 circuit from the panel. Most of that was modding the bench.

Now to clean the thing up, turn a missing sight glass for it's oil system, (how cool is that...kinda like towing your Locost...with your Locost!), run a 220 circuit that actually meets code , and order a few accessories. Oh, and maybe reinforce the bench a little more. In fact, I think I'm going to weld up a bracket to tie it to the wall. I'm confident in the strength of the bench, but a little terrified about it tipping over on me as a result of some series of unfortunate events.


-dave "glowing" hempy

ps. Anybody want to buy a barely used, pre-tuned, well accessorized 7x14 lathe?

_________________
...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]

Just a quick self-motivational post to remind myself I am indeed still building a car!

Tinkered with the front suspension some more last night, and decided to stop analyzing and start cutting. I'm going to use the drawings Jack posted at http://www.kineticvehicles.com/DwgFrontSuspension.htm . I had planned on ordering from Kinetic, as everything else I've ordered from them has been so good, but I'm just too danged squeamish about finalizing the suspension design. I figure if I build it myself, I can afford to make a few mistakes along the way, and in the meantime have some tangible progress.

I also mocked up a pushrod suspension in 1/4" foam-core poster board. Much sturdier than regular poster board...I recommend it for prototyping. I've got about 2" of shock travel to play with on my 'busa shocks. My current design gets just over 4" of wheel travel. I may try to get it up over 5", but we'll see.

I calculated the motion ratio of ~ 2:1 at full bump. All the angles change from there to full droop, one of them (shock to rocker arm) changes dramatically, so I'm not sure it will pan out like I'm hoping. But I kind of held things in place at full droop and eyeballed it and I think I'm in the ballpark.

Is it common to have symmetrical amounts of bump and droop from ride height? I've been mocking up +2 and -2 wheel travel, but now I'm wondering if something closer to +3 (bump) and -1 (droop) would actually be more useful. Thoughts?

I forgot to take some photos last night...I'll fix that tonight.

I bought steel today for control arms. I've got 24' of 2.5" x 1" x 0.065" tubing for the lower control arm. Metal Supermarket doesn't carry that size, so I had to get a whole stick at the big steel yard. If anybody needs a few feet, I'll make you a good deal.

The guy in the yard laughed at me when I told him to just set the 24' stick on the ground. That's okay...I thought it was funny he used the 50 ton gantry crane for a 40# stick of metal. He laughed even more when I got out my extension cord and angle grinder and proceeded to cut the stick and load it. I explained I was the cheapest [Fatherless Child] he'd meet all day and I'd rather buy lunch than pay a $7.50 cut charge. He agreed and helped me load the pieces.

-dave

_________________
...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]

Hows the lathe doing? That looks like one heck of a home work shop machine.

Thats a tough call on the travel. On a rough road, you may spent a lot of time on the bump stops with 2" of bump travel unless you run some stiff springs. Then again 1" of droop may leave a wheel hanging in the air in roll.

Any idea how the Busa dampers do with that motion ratio?

_________________
-Andrew
Build Log
Youtube

Real nice. I've got it running well and have turned out some nice play pieces. I made a tie rod extension on it. I'd made a bunch on my little 7x14 lathe and wanted to compare. The finished product is no nicer than the first batch, but it is soo much nicer working on the big machine. The actually cutting doesn't seem much faster/nicer (maybe I just don't remember how long it took before?) but it's a lot easier to deal with. Easier to mount the work, easier to run the machine, less screwing around, just more pleasant all around. When it came to cutting threads, the extra power made it a SNAP! I can run the tap and die directly under motor power, each step took under a minute, after set-up. This was a 10 minute step on the little lathe, or a five minute step in the vice.

I bought some brass today at the metal shop. I'm looking forward to playing with that a bit. There are two levers on the lathe that NEED to be replaced...they will be much nicer in brass than the rusty bolt currently assaulting my hand every time I reach for it.



No, I have no idea! These shocks did come off Mark Rivera's car in a very similar bell-crank/pushrod arrangement. (as in...I'm basically copying what worked for him!) His was used exclusively for autox/track use, so I don't think it's not exactly comparable to the more abusive street use I'm looking at, but should be in the ball park.

You can see his set up here: http://rivera.fotomojo.us/g/MX7/3_28_06_001 (and the two pages prior to that one). Mine will be pretty similar.

Mark's front end:



-dave

_________________
...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]

Okay...don't view this page if you get car sick easy. This is a good example of how NOT to make animated gif's.

I took a few shots of my rocker prototype at ride height, 2" droop, and 2" bump. Stitch 'em together, and this is what you get.

_________________
...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]

This is how I designed my pushrod suspension. Details in the next post...

_________________
...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]

I planned to create a spreadsheet (might still) but found a pencil and calculator was adequate.

I simplified by measuring the angles in situ at ride height, max bump, and max droop, instead of building a computer model or calculations to compute them throughout the range. (As if I have the skills to do that!) That made it a one-hour job, instead of a who-knows-how-many-day exercise.

I didn't find any pushrod suspension calculators online (didn't actually look that hard). I made up the calculations to find the motion ratio (wheel travel/shock travel)...they may not be perfect, but they proved close enough, and matched observations on the car. This is the formula I came up with:

Points A B C D E F G are shown in the diagram below.

ST = Shock travel = displacement of B. It turned out easier to measure the displacement of A (not fixed to anything, and the spring is not actually being compressed here), which is about the same thing since the shock barely changes angle.

WT = Wheel travel = displacement of F (Lower ball joint).
(vertical displacement is nearly identical to total displacement here, so I treated them as the same)

The shock has 2" of travel, so I called ride height the center of that range. At max bump, B is displaced +1"

Len(BC) = 3"
Len(CD) = 4"
Rocker ratio = 4" / 3" = 1.33

Len(GE) = 14"
Len(GF) = 18"
LCA (Lower Control Arm) ratio = 1.23

At max bump Angle(DEG) = 70 degrees.
sin(70) = 0.94

I set the rocker arm up so that angles ABC and CDE come up to 90 degrees as we reach max bump. Not only does that yield a rising rate (if I understand this stuff right), it simplifies the math! At first I guessed that would make the rocker angle BCD around 80 degrees, but it turned out to be about 60.

SO....

To compute the wheel travel (WT) from shock travel (ST), I came up with:

WT = ST x Rocker ratio x sin(DEG) x LCA ratio
(note, this only works at max bump, where the angles at the rocker arm are 90 degrees)

At max bump, ST is 1" from ride height, so WT is:

WT = 1" x 1.33 x 0.94 x 1.23 = 1.61

So the overall motion ratio (at max bump) was 1.61:1.

This matched what I was observing on the car. With only 2" of shock travel, I wanted more than 3.2" of wheel travel.

First I moved the lower pushrod point (E) in so Len(GE) was 13". That gave me a motion ratio of 1.77, and wheel travel of 3.5"

Then I shortened the BC to 2.5" so the rocker ratio was 1.6. That got me a motion ratio of 2.14 and wheel travel of about 4.3". I'd like to get it up to 5" for street use, but I think this is at least close enough to run with.

I didn't compute anything at ride height or droop. Just playing with the prototype, it didn't look like anything was going to change too radically from max bump, formula wise, and...well...it was already 3 AM! I think it will work out just fine.

I'm going to start fabbing up the goods next time I get to spend some time in the shop...hopefully before the weekend. I'll keep you posted.

I hope this helps someone, and if anyone sees any mistakes or a better approach, PLEASE teach me!

-dave

_________________
...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]

Finished my first upper control arm. All in all, I'm pretty pleased with it.

I think I need to break down and buy some good drill bits. My instructor warned me that my HF drill bits tend to drill oversize because they're not ground very accurately. The 3/8" hole for the AN6 pivot bolt yields a bit of slop. Definately more than the simulator parts that Jack loaned me.

This is really annoying, as I didn't realize it until I finish welded the entire assembly, so I can't just make a new tab. Well, I guess I could, but I'm inlined to just make a whole new part. Oh well...I went into this expecting to scrap the first one.

Would it be okay if I left everything tack welded until after my first test drive?

-dave

_________________
...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]

Got some good hours in today. I've finished an upper control arm, described above...although I'll probably redo it because of the slop in the pivot bolt. Maybe I'll drill it to the next size, but I don't think so.

I've made all the components for both lower control arms...2.5" tubes, 1" tubes, gusset plates, bungs, grind down lower ball joints. One of the gusset plates came out too short (me=dummy), so I'll do that one over. I didn't bother making lots of nice curves and such. I'll probably regret rounding off the end of the bracket, behind the 3/8" bolt, after I kick it once or twice. I think I'll go back and grind those down.

I welded on one of the gusset plates before calling it a night. Looks good (if you don't focus on the welding too much...) Forgot to take pictures...will fix that tomorrow.

One thing I've learned...it's worth buying these pieces as a kit from Kinetic. It's amazing how much time can go into being too fussy over details that don't matter.

More later,
-dave

_________________
...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]

Buy a set of step drills Dave. They drill much rounder holes (from my experience) and are like having a full set of drill bits in one. I think I paid $8 for a set of HF ones and they are just as good as the set of Unibits I have a work.

Looks good. Keep it up!

_________________
He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

Hmm...Good thinking, Chet! I have the same set, and will turn to it next time. They do make very round holes.

For the gussets, I made all four at once, so the step drill wouldn't reach through them all. When I drilled the 3/8" hole for the AN6 bolt in the lower control arm, I drilled it a few sizes too small, then used an end mill in lieu of a reamer to finish it out. That worked well, but only because 3/8" is one of the dozen or so end mills I have. If it had been a 29/64" or some cockamamie size, that would have been more challenging!

-dave

_________________
...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]

I zipped through your suspension posts quickly so maybe I missed it, but I didn't see a squared term on the motion ratio. Also, the motion ratio is only part of the picture. You can make the wheel travel however many inches you want, but the resulting wheel rate may be unacceptable.

Bike shocks wouldn't work for me due to this and I was unable to turn my 600lb/in, 1.7" travel bike shocks into 5+" travel 120lb/in wheel rate. Ended up going with 6" travel QA1s.

_________________
Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

You wouldn't be the first, but even more critical--replace the PVC components with mild steel before going into traffic. I was somewhat surprised to discover that my Miata-powered chassis would roll around the shop on PHC control arms, but I doubt they would handle the rigors of the street (speed bumps, pot holes, curb strikes etc).

PS--Also, you could probably turn the power down on your MIG if you clamped the ground somewhere else.

_________________
Locost builder and adventurer, and founder (but no longer owner) of Kinetic Vehicles