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The Buchka 242 Fake Racecar

They're Cannondale MX440 rear dampers.
Such an epic over-reach on Cannondale's part. The old man built up a very successful and profitable bicycle company, the kid kept hanging out with the Dh race team and got a crazy idea in his head to branch out into dirt bikes and ATV's, they hocked the bike company to do so, it flopped, and they lost control of the bicycle company.
 
Damn my KTM quad has Ohlins on it. They pop up forsale on the ATV forum all the time for relativly cheap. I didn't realize Cannondales ran the Ohlins also.

Jordan
 
The build is continuing to make good steady progress since the last time I checked out this thread.

The engineering work involved alone is surely producing some of the most professional, high quality results that could be found anywhere on such a tight DIY-sized budget. Even allowing for the fact that you often have direct access to the kind of equipment that many of us could only dream of, this is the epitome of an inspirational thread for anyone considering doing something along similar lines, even if most likely at a considerably more basic level.

I'm very much looking forward to watching it move on further and closer towards completion.

Great work guys, keep it up.
 
Things are going slow as usual. I have a full time job in Los Angeles that keeps me pretty busy but I've been back in MA for the holidays so Karl and I did some work:

Assembled the starter and mounted it to the bellhousing with the correct lash:
photo%25201.JPG


Lately both Karl and I have become disenchanted with the idea of keeping the stock "frame rails" on the car and patching up the half cut-out floor. Mostly because it will be more or less impossible to quantify the chassis stiffness until the frame is completely done and can be tested. Also, the more I looked at the cruddy floor pan and firewall sections, the more I saw nothing but a piss-poor compromise that wasn't going to work well or look good.

I drafted up a proof of concept for a tube chassis, re-using most of the existing cage tubes until I was reasonably happy with load paths, triangulation, room for the driveline and driver/passenger.

The floor of the chassis is all straight mitered 2x2x0.065" and 2x3x0.083" ERW to make fixturing easy. The "drivers cell" is 1.75x0.095" DOM and the rest of the chassis is a mix of 1.5x0.065" DOM, 1x0.049" DOM, and .75x.75x0.065" square.

I'm going to break my own personal rule of not posting CAD screenshots. Here's one of the draft quality versions that started homing in on the final layout:
a0001_aa_242_fake_race_car6.JPG


Making a stiff enough chassis that's also light is a bit of a brain buster, especially when you have to work around silly nuisances like an engine, transmission, and people.

I ran a really simple first cut beam analysis in Solidworks so I could iterate fast and get a rough idea of the stiffness:
fem%2520screenshot.png


These results gave us enough confidence to start building the chassis. At the same time, I'm now working on a much more comprehensive analysis model in different software that doesn't suck.

Chopping up some tube and laying it out:
photo%25201.JPG


photo%25203.JPG


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Both halves tack welded and roughly positioned:
photo%25202.JPG


Dropped the body and driveline on the table just to see how it would look:
photo.JPG
 
Looks almost like a good solid FIA rally cage especially with the doubled up a-pillar bars. And some suspension support thrown in of course. :p

Interesting that you laid the main rectangular rails down on their sides. Concerned about interior headroom or...?

And I think you've reached the point of no return with the body. Volvo NASCAR is only a few easy steps away now.
 
As the resident Super Cage Design Genius, I approve.

That's going to be one solid cage. I assume you will be using sheet metal gussets though. Ball dimpled holes and all!
 
Replace "knoife" with "cage"

<iframe width="420" height="315" src="//www.youtube.com/embed/01NHcTM5IA4" frameborder="0" allowfullscreen></iframe>
 
Thanks guys! Karl and I are really excited about the chassis. This feels like a good way forward for the car.

Looks almost like a good solid FIA rally cage especially with the doubled up a-pillar bars. And some suspension support thrown in of course. :p

Interesting that you laid the main rectangular rails down on their sides. Concerned about interior headroom or...?

And I think you've reached the point of no return with the body. Volvo NASCAR is only a few easy steps away now.
The base design of the cage was derived from the FIA group N manual. I think it's a great jumping off point for a safe and sound design.

The outer floor members were laid down flat to simplify mounting of the existing main hoop and front main stays.
As the resident Super Cage Design Genius, I approve.

That's going to be one solid cage. I assume you will be using sheet metal gussets though. Ball dimpled holes and all!

I'm going to mess around with gussetting in the detailed analysis to see where it makes the most sense.

y no round tube?

Ease of fixturing on the table, simpler to add hard points, much easier to mount shear panels and to graft onto the existing sheet metal. cost was also a small factor.

When solidworks shows the results of a beam analysis all the elements are given a generic round cross section. The frame members all have the correct cross section attached to them for the calculations.

Is the x design for the door bars the final plan?

Yep. Tieing into the front main stay above the bend is a small compromise I had to make in order to re-use the existing tube arrangement.
 
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