Motive's Open Source Middy
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Author:  motive [ January 2, 2009, 2:26 am ]
Post subject:  Motive's Open Source Middy

Happy New Year Everyone!! I thought I would start out the year by starting my build log, and I am the first new one of the year! It will also make it easy to see just how long I take with this project.

As some might have noticed from the subject line, I have decided to make my plans openly advailable! Its just my way of giving back to the locost community since it has helped me so much with my design so far. I will make drawings advailable after I have fabbed the particular section. That way anyone who wants to follow down my dirty footsteps won't have to wait till I am done first. This does come with some consequenses thought. I have no idea if the end result will work well so anyone using my plans is advised to do there own research on suspention/chassis design and deside for themselves if my design will work and satisfy a reasonable level of safty. (Start with Kurt's Kimini Book, its one of my favorites.) I will not take any responsibility for anyone useing any information I make advailable.

I also plan on making advailable certain parts of my design that would be hard to duplicate without a machine shop. I have been looking for a reason to go to the tax man with receipts for the thousands I have spent on CNC machines. I am a contractor by trade and with houseing sales slow, money is tight so I am also doing this to keep my project going. This will be a true LOCOST build for me and I would like others to be able to build a middy that is affordable to anyone willing to spend some time on it. With that said, I will not get you halfway into the build then drop the line "now you need my (insert part name) and it will cost $$$$$$." The most complicated part will be the spindles which is why they will be the first thing I show you.

Finnaly, everyone is invited to post here any comments, ideas, or concerns you my have (expecialy regarding safty). I am opening myself up to public ridicule and humiliation, so please be nice with anything you post. If there is any Flaming I will ask you to leave. Now lets get started!

Author:  motive [ January 2, 2009, 3:35 am ]
Post subject: 

Now to describe what I will be building. I will be following the layout and styling ques of the KTM X-Bow. I know that not everyone likes how it looks (Giant pissed off cockroach) but I love the thing. Its modern looking, aggressive, original, and not advailable in the US! Of course mine will be a tube frame instead of a CF tub. Pushrod front suspention is strait forward with no sideloading on the rocker. Cockpit bends outward for elbow room. And most importantly, the bodywork could be created with sheetmetal with no compound curves. No Composites!

Technical data on my design:
Ground clearance-4.5"
Weight goal-1300lbs
Tires-24" (205/55R15, 215/40R17 ish)
Wheel offset-38mm
KP inclination-3.78deg (adjustible)
Caster-4deg (adjustible)
Trail-1.19" (adjustible)
Roll center front-2.04"
Swing axle length-68.2"
Roll center rear-3.5"
Ackerman-100% (adjustible)
Seat width-19+"

Donor parts
Dodge caravan: steering rack (full length!), rear bolt on hubs, steering column (optional), front brake rotors.
I chose these because I had a wrecked van that a friend gave me, they are more common that stupid people which makes parts cheep, and they just seemed to work with what I had in mind.
My engine is from a 85 Camry thats been housing mice and rabbits behind my house for the last 2 years. If I come across a great deal I'll upgrade to something that has more than 98HP.


File comment: last day of its life
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File comment: To be reincarnated to something like this
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Author:  motive [ January 2, 2009, 3:54 am ]
Post subject: 

I have been planning/designing for just over a year now. In that year I have also had our second child, finnished the basement by myself, built my wife a table and a bed, rebuilt 3 motocycles for other people, and got rid of every other thing on the "honey do" list I could. I the last 3 weeks I have stripped my downer, built a build table (I highly recomend useing steel studs!) put shelves in the garage, built a rough mockup, and started on the spindles.

File comment: HINT: measure the engine centerline before you take it out.
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File comment: got to love CNC!
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File comment: still needs top and bottom inserts
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Author:  IndyJoe [ January 2, 2009, 11:37 am ]
Post subject: 


Looks like a good start. Glad to see you've started a build log. I think it's a cool thing to make all your plans available to the locost community. I'm eager to see where your going with the uprights/spindles. Did you design them with a CAD program? Which one. I like your mock-up there in wood? Is it going to be single seater, or did you only mock-up half the car?

Indy "let the fun begin" Joe

Author:  JagLite [ January 2, 2009, 12:00 pm ]
Post subject: 

Great start :!:
Keep the posts coming
We will be reading and learning

Author:  KB58 [ January 2, 2009, 10:31 pm ]
Post subject: 

What's the steering ratio of that rack?

Author:  motive [ January 3, 2009, 1:08 am ]
Post subject: 

Sorry, you'll have to wait to see how the uprights come out. I ruined my endmill I was using to cut with and the way I programed the radiused corners forces me to use a specific size endmill. I will tell you that how I designed it, it will be self-jigging for the inserts that are going to get welded in the top and bottom. The top incorporates the balljoint and steering arm in one piece. You shim that arm to the rest of the upright to change camber. I designed them with autocad as its the easiest to take to the mill for me. I also use solidworks.

I guess its not clear from my mockup, it will be a two seater. Only mocked up drivers side since that is were all the action takes place. (Since there is no "back seat" :lol: )

Kurt, the rack moves 1.8" for every turn of the wheel. It has about 2 1/2 turns lock to lock. 28.5" between tie rod centers. I designed the uprights stearing arm length to provide 15deg of steering for every inch the rack moves.

Author:  horizenjob [ January 3, 2009, 9:17 am ]
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I wish we could get this going in Sketchup, so be more open source, or at least cheaper software. Seems difficult to get from sketchup to the mill now, as I understand it....

Author:  KB58 [ January 3, 2009, 12:48 pm ]
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Only the $600 Pro version of Sketchup outputs .DXF file format.

Author:  horizenjob [ January 3, 2009, 2:08 pm ]
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KB, maybe that means everyone can sketchup, and only machinists need the Pro version?

Author:  motive [ January 6, 2009, 12:12 am ]
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horizon- Why do you wish it would be in sketchup? I am planning on making the drawings in a format that anyone can view without a cad program. Most cad programs have a free "view only" version. Solidworks for one.

I got alot done this weekend. I did some improvements to my mill, added flood cooling. Should increase the speed I can cut parts and I won't have to stand there with a bottle of cutting fluid the whole time. I just hit the go button and go to work on something else while the "slave" cuts perfect parts.

I also took my finnal measurements from my mockup. Did make some changes based on how everything fit together. No matter how well a human figure seems to fit in a cad drawing, it doesn't seem to work out in real life. The mockup is gone and I'm starting in steel tonight. I have to say its hard to start making those permenant cuts and welds when your going off an original design. Always second guessing every decision,dimension, and tube placement. I have vowed to not get the dreded "analysis paralysis" though so I'm off to the garage now to have some fun!

Author:  ericd735i [ January 6, 2009, 12:26 am ]
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Looking forward to seeing your progress as I also want to use styling cues from the X-Bow.

Author:  motive [ January 9, 2009, 12:50 am ]
Post subject: 

A little update to let everyone know I have gotten some stuff done. Burnt out the motor on my HF bandsaw so instead of breaking out the chop saw to cut more tubes, I desided to fully weld the base. Somehow it came out with only about 1/16" of twist. Started by tacking the sides of the tubes only. Then welded the sides before doing the top. I was very surprised it didn't warp more. I does look kind of funny because the base sides are parallel but when the upper tubes are added between the front and rear roll hoops it will give it some shape. Still waiting for some mills from Enco so I can finnish the uprights.

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Author:  motive [ January 12, 2009, 3:40 am ]
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Didn't get nearly as much done this weekend as I wanted. Fixed the bandsaw ($3.40 motor start capasitor from Grainger, tell tale was the motor would hum and vibrate but not spin, actuall starts faster than when new.) Updated some of my CAD drawings to the finnal dims. Welded on the two front bulkheads. I built the bulkheads in the center of the car on the table but used a sub-jig to hold them in place when I tacked them to the frame. It worked realy well because I marked a center line on both the table and the bulkhead jig, then just lined up the lines to get perfectly placed bulkheads. You can also see in the pictures the legs I screwed to the jig to hold them square to the rest of the frame. It left both hands free to do the welding. I'm hoping the guy bending my bars will be able to get it done early this week.

welding bulkhead 1&2.jpg
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File comment: notches cut in jig to fit over frame rails for the second bulkhead
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Author:  KB58 [ January 12, 2009, 10:15 am ]
Post subject: 

Leave off the inboard suspension mounting brackets until last. Welding heat can (will) distort the chassis to an amazing degree. Figure up to 1/4" in places.

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