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Author Topic: Bockscar 2.0  (Read 5940 times)
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jdincau
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« Reply #60 on: October 27, 2017, 01:54:26 PM »

Thomas;

What is "CREMONA"?  huh

Regards, Neil  Tucson, AZ
https://en.wikipedia.org/wiki/Cremona_diagram
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« Reply #61 on: October 27, 2017, 02:31:56 PM »

CREMONA?

1. this Wikipedia note is maybe 10 percent of what Cremona really is.

2. Cremona is a mathematic rule for frame design.

3. mathematic rule for a compression strut - tension member - reaction and counter reaction
    you got a frame - on one point of the frame you put an energy on - the result - this part of the frame likes to move/escape.
    other parts of the frame are involved into a force reaction...one part of the frame will be length other compressed....
    they all like to escape from that force and finally somewhere the force will "go out" on a other area of the frame...

    simple!

    yes, it is maybe a little bit more complex....but the easiest way to say what happens in a frame construction

4. the base idea behind Cremona is:

    - with the same weight done right to Cremona you can get a double stiff construction as a poor design

    - or with half the weight the same stiffness as the poor design

5. in a combination you can design a frame which is in one area very stiff in an other area very flex

    Jack Costella is here a real master....I don't know if he ever heard from Cremona...I think what he is doing is just the result of thinking outside the box.

6. Cremona is the base mathematic rule behind all crash simulation programs...


Now, why I said to the Bockscar design....the reason for the roll bar design is Cremona.

 - what would be the reaction in the frame design if the roll cage would be only on the top cross member.....

   thinking about the racer rolls sideways, full contact of the top of the roll cage with the ground....if there would be no connection to the bottom cross member the top cross member would be pressed "down" (to the bottom one) and the side wall frame tube would be bend inside and the whole frame system would collapse.

Now the roll cage frame tube is going down to the bottom cross member - same rolling situation - the top and bottom cross member with the connected roll cage tube is creating a very strong frame (rectangular) which can absorb a high power input....the outside frame tubes creating also a strong frame - both - cross frame and main frame combine to more stiffer combination....the compression strut and tension bar in this frame works against the force of touching the ground.....the top cross member will be not bend down and the outside frame tubes will bend not inside.....


The Cremona rule helps to get the members and cross members to the correct position where they work together to create a frame system which pick a high force input without bending......

in the same way you can weaken an frame area so the part will bend and reduce the force on other parts of the frame as also slowing down the deceleration to protect the driver



Sorry, Cremona is tough to explain and it needs you a long time to understand the idea behind....but used the right way it is a fantastic tool to create a racer frame.
« Last Edit: October 27, 2017, 03:05:30 PM by PorkPie » Logged

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Stainless1
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« Reply #62 on: October 27, 2017, 03:09:57 PM »

Wow, learn something new everyday.... but then I drink my coffee black.... Oh wait, that's Cremora  rolleyes
OK my original answer is I hope it gives me more room in the cockpit and fit inside the canopy as well as provides strength.  Here are some old frame shots, the front hoop is tough to make at the size it is.. wider will be harder and I don't think stronger to make it the old way.  It interferes with entry and exit, and the braces pinch your arms in... leaving bruises on all including Thomas.
I'm thinking I have the bars attached to the top and bottom rails making it stronger.... did I mention I don't do this stuff for a living...
The old one didn't kill anyone, hoping the new one will last as long and never hurt anyone either.


* Oldbframe1.jpg (161.15 KB, 637x849 - viewed 97 times.)

* Oldbframe2.jpg (181.9 KB, 530x706 - viewed 116 times.)

* Oldbframe3.jpg (147.23 KB, 502x669 - viewed 99 times.)
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Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
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« Reply #63 on: October 27, 2017, 03:18:21 PM »

Yep, learn something every day. The only "Cremona" I was familiar with was the violin maker.

Regards, Neil  Tucson, AZ
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Regards, Neil  Tucson, AZ
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« Reply #64 on: October 27, 2017, 03:33:05 PM »

Hope, my explanation is understandable....how Cremona works....and yes, Cremora is the strong way to drink your espresso.....


Yep, learn something every day. The only "Cremona" I was familiar with was the violin maker.

Regards, Neil  Tucson, AZ
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« Reply #65 on: October 27, 2017, 07:36:54 PM »

I think Pork Pie has somewhat oversold Cremona.  Classically, it is a graphical technique to determine the loads in the members of a planar truss taking into account the applied loads and locations, the reaction loads and locations, and the geometry of the (proposed) truss design.  It is basically static analysis of the framework.  Once the member loads are determined, that information can be used to size the members for their appropriate tension or compression capacity. 

In the U.S. this is normally simply termed static analysis.  However, it may be that in Europe the Cremona name is used more popularly due to its origination in Italy.

In this day and age, manual analysis of this sort, which is laborious, has been supplanted by Finite Element Analysis programs which, for spaceframes, is an automated version of the same technique but also is more advanced in that it takes into account the elasticity and deflections of the members.   (Which can also be done manually, but is REALLY laborious, iterative, and open to human error.)
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« Reply #66 on: October 27, 2017, 08:15:06 PM »

IO;

Thanks for the explanation.

Back in the late '60s I built a chassis for a small Corvair-powered Sabel mid-engine sports racer. I used a computer, an IBM 360 Mod 50, to do the stress analysis on the tubular space frame. We had a program called "STRUDL" that was an early structural analysis program. All structural members were defined on punched IBM cards; the stack of cards was about 7" high and the program on this big mainframe ran overnight during unused periods. The output was on fan-fold printer paper that was about 3/4" thick. We've come a long way since then! I think a desktop personal computer could probably do the same job in less time these days.

Regards, Neil  Tucson, AZ
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« Reply #67 on: October 28, 2017, 02:50:58 AM »

IO

just to tell you

FEA is currently the final USE of Cremona and another mathematic rule - STEINER

FEA based on this two rules.......

FEA is nothing other than the name of a Computer Program....it also had could call STUPID CRASH DUMMY....

....because, reading FEA results creates more human error, than making a Cremona calculation by hand and with your mind


I'm working now for more than 30 years with Cremona, Steiner and FEA....the biggest risk is the HUMAN who use this tool..... rolleyes




I think Pork Pie has somewhat oversold Cremona.   by Finite Element Analysis programs
« Last Edit: October 28, 2017, 02:53:43 AM by PorkPie » Logged

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« Reply #68 on: October 30, 2017, 02:25:15 PM »

The "state of the art" in tube chassis fabrication are off road race trucks. I have attached a pic of a truck chassis being built at the Herbest Brother's shop in Huntington Beach. Note a couple of things: 1. No tube connects to another tube without an additional tube attached such that it will carry any load from the first tube to other parts of the chassis. 2. Look at the tube joints where multiple tubes join together, each tube has "overlap" of the other tubes, not easy to do but it provides the strongest and stiffest welded joint. 3. There are no plate gussets, they are stress risers and an admission that the joint was not properly designed.

Stainless,I realize that this type of frame is pretty far from what you are building for the new Bockcar but you should be able to get some good fabrication ideas from these pics.

Note the pic of the multi tube joint, one part of the coped tube was cut off to be able to install the tube and then re-welded into place to make a perfect joint! Now that is detail.

Rex


* Truck fab 7.PNG rr.PNG (189.71 KB, 235x299 - viewed 151 times.)

* Truck fab 23 red.jpg (182.69 KB, 930x637 - viewed 170 times.)
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« Reply #69 on: November 07, 2017, 01:33:53 PM »

Yep, really nice work... and yep, if I used that much tube there wouldn't be room for a driver.... rolleyes
I am back from my wine country trip so I will be back to work on the lakester later today. 
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Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
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« Reply #70 on: November 08, 2017, 09:26:24 PM »

 cheers
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« Reply #71 on: November 12, 2017, 10:56:56 PM »

I suspect y'all think I've been eating Bon Bons and drinkin' whiskey all day, the truth is not far away....  rolleyes but a little progress has been made.  Still looking to bend or get the roll bars bent, searching for the right bending guy, Johnboy is starting to look in Denver, I am checking a guy up by KC next.  I think I want an 8 inch CL radius but maybe I really want 7.5  undecided  Need the roll bars soon to keep moving.

Still getting a little done during all the research, search.... and re-search

Added some floor bars made from 1.5 x 1 x .125 wall.  They will get a little triangulation besides the seat back bar.


* btable11.jpg (188.16 KB, 588x784 - viewed 49 times.)

* btable13.jpg (144.09 KB, 521x694 - viewed 55 times.)

* btable14.jpg (159.07 KB, 530x706 - viewed 44 times.)
« Last Edit: November 12, 2017, 11:29:20 PM by Stainless1 » Logged

Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
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« Reply #72 on: November 12, 2017, 11:10:27 PM »

Then the seat got checked... I guess I should run by to see Max, check on his bike progress and borrow his English Wheel to see if I can flatten a couple of the seat panels that seem to have Johnboy's hip and butt prints dimpled in.  Yep he was snugged in tight, but belts stretch a little and let him flop a little.


* btable12.jpg (166.49 KB, 564x751 - viewed 93 times.)

* btable9.jpg (146.03 KB, 510x680 - viewed 68 times.)

* btable10.jpg (140.91 KB, 510x680 - viewed 79 times.)
« Last Edit: November 12, 2017, 11:15:03 PM by Stainless1 » Logged

Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
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« Reply #73 on: November 13, 2017, 10:20:52 PM »

Nice clamps under the back of the seat grin
« Last Edit: November 13, 2017, 10:29:38 PM by Speed Limit 1000 » Logged

John Gowetski, red hat @ 221.183 MPH MSA Lakester, Bockscar #1000 60 ci normally aspirated w/N20
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« Reply #74 on: November 13, 2017, 10:27:41 PM »

Stainless;

Was your seat 6061-T6? What thickness did you use?

Regards, Neil  Tucson, AZ
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Regards, Neil  Tucson, AZ
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