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 Post subject: Rear structure
PostPosted: February 12, 2009, 1:15 am 
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Location: Mahomet, Il
I got the rear structure buttoned up. The new pictures show the rear structure much better.

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Not alot of progress, but every little bit counts!

Thanks for looking,

Daniel

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PostPosted: February 27, 2009, 2:15 am 
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I've been working on the suspension/steering. The stock MG uses a straight collapsing column for steering that I wanted to try to maintain, however with the low steering arms on the RX-7 uprights I couldn't due to the rack being on the bottom of the chassis. The MG uprights steering arms are a bolt on affair that bolt with 2 bolts perpendicular to the upright. If I mount the steering rack on the underside of the upper frame rails I can run the stock column just shortened, and my rack length becomes much closer to correct at only about 1" wider than the inner upper bushings. So enter the stock MG steering arms as the solution to all my problems. I mount them on my upright adapter, get easy adjustable ackerman, the correct steering arm length, and I can put the rack right under the upper frame rail. Sounds like a win win win.. Except the Shocks/bellcranks have to move. So I had to go back to the drawing board on the bellcranks/pushrods to get the shocks to work. A week later I think I found a mounting that will clear the steering column, rack, and tie rods, and as an added bonus look sweet. Unfortunatly I don't have any pictures of the steering mocked up, however I do have some of belcrank construction. Once again I used the plot and cut approach, ploting out my belcranks at 1:1 and drilling holes and cutting the shape on the bandsaw at work. For the belcranks I wanted to be able to easily adjust the WR for fine tuning the handling balance of the car and for street vs. track. I'm doing that by slotting the pushrod side and putting a threaded adjuster on. Although slotting without a Mill or waterjet is hard.
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First drill two holes at the ends of the slots
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Then cut across the holes with a Jab saw, or disassemble your hacksaw
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Go crazy with the hand file and Viola
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Slots!
Believe it or not each slot only took about 3 minutes.
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Here are the sides of the front and rear bellcranks.
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This is the new mounting position I came up with for the front shocks. It will require a few more tubes to be fitted, but It will look sweet with the shocks all horizontal up by the engine, not buried under the radiator. They will also be easier to adjust which is a bonus.

Since I have the shocks Planned pretty well I decided to get the engine mount started in preparation for rolling chassis day. The engine mount is shown bellow. It will be pretty basic. A sheet of heavy steel with 3/4" .120 wall tube welded to the end for 1/2" bolts to run through a flange on the chassis cross member.

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Well that brings you all up to date. A lot of the work for the past couple of weeks has been mental stuff figuring out how to get around issues that pooped up. Special thanks to Jack at Kinetic vehicles for getting me 1/2" rod ends for the pushrods. I got them 2 days after I ordered and can't wait to put them to good use.

Thanks for looking!

Daniel

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PostPosted: February 27, 2009, 12:39 pm 
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Joined: January 22, 2007, 5:13 pm
Posts: 313
Location: Anchorage Alaska
Keep the updates coming!
I am reading and examining all that you do.
I like the lowcost tools you have since that is the situation I am in.
Lots of woodwork tools but my metal tools are very limited.
Angle grinder, steel chop saw, drills, and a mig welder....

But, amazing things can be done even if we don't have the mill, lathe and other great tools.

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PostPosted: March 8, 2009, 3:26 pm 
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Joined: July 14, 2008, 9:07 pm
Posts: 228
Location: SW FL
Daniel,

I've read your build with interest. I gotta ask, have you considered widening the body at least some rather than such massive fender flares? Seems like it would all be pretty straight forward cutting it right down the middle but leaving the cockpit unaltered from its curent configuration.

Great work so far,
Mike


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 Post subject: Levitating Engine
PostPosted: March 12, 2009, 1:24 am 
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Location: Mahomet, Il
I've been working on getting the driveline mounted to the chassis on my march to roller day. I completed the front engine mount and made a trans mount. The mount is a piece of 1" tube with a .188 flange with some gussets. This is screwed into the stock trans mount holes in the trans. At the end of the 1" tube is some 3/4" .125 wall DOM that 1/2" x 2" bolts go through and bolt to a piece of 1.5 x 1.5 3/16th angle. I will probably add a rear gusset to this piece to stop the trans from moving backwards when I install the engine/trans. I might use a weld-nut on the chassis flange, but am more comfortable with a actual nut, as I don't want to risk stipping out a weld nut. These pictures also show the driveline angles. The driveshaft runs very slightly down and at a very slight angle. I think it's pretty good. I was really excited when I removed the last block of wood holding up the engine and put it's full weight on the chassis for the first time. The engine is officially floating. Now I will get the front diff mount done, and then tackle shortening my own driveshaft.... .. Wish me luck!

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The mount here is incomplete. It will have a pair of tubes going to the upper bottom rail.

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The red pieces are from my MS Paint/E CAD software showing future reinforcements to the trans mounts.

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JagLite thanks a lot for the compliments. I learned from my dad that just because you don't have the best tools doesn't mean you can't get good work done. I have access to a lathe at work, and one of the Model makers in our model shop has offered to mill parts for me. However I take pride in doing work with minimal tools (although I did have him mill a hex into some bungs for the pushrods). All of the compound tubes on the chassis have been fitted by hand with a hacksaw and hand file. I feel fortunate that I've been able to accumulate the amount of tools that I have, and it's good to know that the work I'm doing is inspirational to others out there without huge tool budgets. There is nothing wrong with having access to a CNC Mill, or waterjet or all sorts of new equipment. I just like doing it the old way.

As to widening the body I seriously considered that at the start of the project, however I wanted to keep the curved MG windshield which meant the door width was set, and I just like the look of a car with huge flares. There is something about them that just speaks to me.

Thanks for looking!

Daniel

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PostPosted: March 12, 2009, 6:48 pm 
So you're solid mounting the engine?

--Chris


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PostPosted: March 12, 2009, 10:01 pm 
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chrisf wrote:
So you're solid mounting the engine?

--Chris


Yes. I had it this way before when it was just a 12a swapped midget. The vibrations the rotary produces are very minimal. I'm not sure if there will be any long term issues brought about by this decision, but I have 3 extra motors and transmissions so If I break anything I can always add a little bit of rubber to allow some flex.

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PostPosted: March 13, 2009, 7:38 am 
Wow! That's hardcore. It will be cool to see how it works.

Do you have any pics of the 12a in the Midget?

--Thanks, Chris


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PostPosted: March 13, 2009, 12:32 pm 
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It's inching ever closer to being a roller! Next up, get that wooden block out from under the front of the diff. ;)

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 Post subject: Progress.. Finally!
PostPosted: April 1, 2009, 12:03 am 
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Location: Mahomet, Il
I got some more work done on the car. (well quite a bit, but More on that later).
I got the steering system mocked up. I'm using the stock MG rack, and the Stock MG steering column. This required me to hack into the chassis above the upper rear suspension node, but It had to be done. The stock MG column is a double collapsing unit, and has no u-joints in it. It took me a while but I finally got it all figured out how I can get the steering wheel in a good spot (almost exactly where it was stock) and get the rack located with minimal bumpsteer. Running the straight steering shaft required me to move my shocks because the rack needed to become High mount, but that made the stock MG rack width work better with the suspension so I didn't have to narrow it (I have ~ .25" of bumpsteer over the full suspension travel). I ended up redesigning the bellcranks to turn the shocks inline with the centerline of the car similar to on a At-om (more on these in the next post). Out at the upright, I originally intended to use the stock MG steering arms. This proved unsuccessful as they would have had to cover up the brake caliper bolts, so I decided to just weld on two flanges on the upright adapter and make my own steering arms. I'm going to add a flange to the back of the upright mount that will get bolted on with the caliper for a little extra rigidity. The pictures only show the top mount. I had to make it so high so it would miss the upright mount bolt. After a lot of messing around, I'm fairly happy with the result.
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Designing new arms also allowed me to quicken the rack up. It now is ~2.5 turns lock to lock, but my lock is 40 degrees of turning, so the steering effort might be a little high. If it is, I know how to make longer steering arms :D
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I estimate ackerman to be ~3 feet behind the rear axle. I did this because Carrol smith recomends running less than true ackerman due to the rear wheel slip angle. He also however says you will push the car around a lot so it's not worth running too much less than 100%. I took this advice and promptly decided eyeballing the ackerman would probably be therefore ok.

I also finished up the bellcranks. You may of noticed the slots that they had when I showed the flat sides. The purpose of the slots was to allow the pushrod leverage to be changed allowing me to fine tune my wheel rates. Adjustment front and rear should be from ~2hz-~3.2hz. It's quite stiff, but I wanted low ground clearance so I can't tollerate more than ~3" of total suspension travel. You can see in the second picture how the adjustment mechanism works. You simply loosen the pushrod bolt, and tighten or loosen the 3/8" bolt. The adjuster bracket is made from 3" of 1x.125 stip, welded together with a 1/2 x .060 wall 1" long piece of tube on the side. I tapped some 3" long 3/8" bolts to have ~1.05" of shank so I could bottom a nylock nut against the shank and give a solid 2" of thread. There is a piece of .188 plate across the bellcrank faces that has a weldnut attached to it that the adjustment mechanism threads too. To finish off the adjuster small spacers of 3/4 x .120 wall 4130 tube are welded on to give the clamping surface for the rod end. The bellcranks ride on a piece of 1" OD solid rod drilled to .75" to accept .75 OD x .5 ID x .75 long flanged brass bushings, riding on a 2" or 1.5" long shoulder bolt. Also of note is you can see the only part I somewhat have farmed out on the whole car. The Hex ended threaded bungs where milled by a friend at work to have a hex on the end. I tapped and turned down the raw part, and created a plate that they all bolted to, and he mounted them in a CNC mill and milled the hex. I was going to do it with a hacksaw... .. But even I have limits.
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Why am I going into such rediculous detail on the bellcranks... Because finishing them took 6 FRICKEN HOURS. It seemed like it should be just a quick task, only take a couple of hours, but there is a lot of small fabrication in each one, so I'm proud of them.. Lets hope they work.

As a total aside I attempted to make a threaded pushrod bung without a lathe, as I thought it would be an interesting challenge. It's actually fairly easy. If you mount a 1" holesaw in a drill press and weld a piece of 1" OD solid rod to a plate, clamp it securely centered on the bit, and go to town it leaves a roughly .75 OD shank, and a nice centered hole to drill out for tapping. So there you go.. No need to spend $5 each.. just make them yourself with no lathe.


Thanks,

Daniel

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 Post subject: No Snappy Tittle..
PostPosted: April 1, 2009, 12:32 am 
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Location: Mahomet, Il
I got the front bellcranks positoned and almost mounted. As I said before I had to turn the belcranks to allow the shocks to load into somewhere near the firewall. I was nervous that this would be difficult to make the chassis have mounts for the bellcranks, and I was right. The wing (as I call it) is at a 20 degree angle WRT the chassis tubes, and cantilevered out 6" from the upper frame rail. The bellcrank is at a further 35ish degree angle to the wing. This led to some swearing to get the flanges and wings to the right positions but I prevailed. Further support will be added to the wings in the form of a tube running down to the lower front suspension point, a tube running down to the lower rear suspension point. But for now they are rigid enough to hold the shocks up and look Sweet! Amazingly I made both sides Identical on the bench and brought them over to the car and they worked. It took a little futzing to get the final belcrank angle WRT the pushrod exactly right, but it wasn't much.
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The Shock Chassis mounts will be a threaded bung attached to the upper frame rail, and then there will be a flange running to the upper footwell tube. I will probably put a small gusset behind the corner to just add that extra little bit of rigidity.

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Driven5 and I were discussing that this style of Pushrod/belcrank would be VERY easy to adapt to a locost. Where most people have their upper shock mount you would mount the "wing" (also would allow a nice hard point to mount your headlights) run a triangulation tube down to the lower frame rail where the lower front suspension bracket is, and have the shock mount to flanges on the upper frame rail right behind the nosecone. It would look sweet all hanging out in the breeze beside the nose.. Kinda makes me wish I was building a locost.. Maybe next project..

As always.. more pictures available at the Photobucket site.. http://s33.photobucket.com/albums/d51/Nocones/midget/

Thanks,

Daniel

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PostPosted: April 1, 2009, 1:02 am 
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Location: Under the weather. (Seattle)
I'm soooo stealing all your cool ideas for my build!...Muahahahaha. :twisted:

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PostPosted: April 1, 2009, 8:04 am 
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Location: michigan
Driven5 wrote:
I'm soooo stealing all your cool ideas for my build!...Muahahahaha. :twisted:

Heck, i wanna steal his whole build! JK
i am really impressed when someone successfully uses bike shocks. i might just use that bellcrank configuration in my build

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PostPosted: April 1, 2009, 11:23 am 
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Very innovative and beautiful fabrication on these bellcranks.
Color me impressed :cheers:

Cool build, can't wait to see it turning wheels in anger.

Moti

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PostPosted: April 1, 2009, 1:38 pm 
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Location: Darboy, WI
Nice work! :P

Next time I see the lights on in your garage I'll have to stop by. I'm always going somewhere when I see you guys out there. Now you guys are welcome to come check out my project car. (Its not that you weren't welcome before, I just didnt have a project car!)


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