Frame Bracing.

[jed.only]

i agree, and i think i finally see what you mean. you talk sometimes in such a way that i just cant make out what your trying to get across, like im missing every other word or something.


think i get it now.

thanks.

[posplayr]

you talk sometimes in such a way that i just cant make out what your trying to get across, like im missing every other word or something.

I'm an engineer

[midnightcafe]

let's not forget that frames are meant to flex as well. A stiffer frame is stronger, but will not react to applied torques and moment forces as pleasantly. I'm going to download that chassis design book, looks extremely interesting:

http://www.demonoid.com/files/details/1816951/775222/

[jed.only]

I'm an engineer

BAHAHAHAHA no kidding?



ah, it makes so much sense now!

[Dreef1999]

BAHAHAHAHA no kidding?



ah, it makes so much sense now!

The moment he said free-body diagram it was pretty obvious

And, pos I don't think the x-z axis is very important but it might be significant enough to justify the bracing at "A" being at an angle.

The headstock is a fairly rigid structure in torsion because of the three tubes spaced but you have 2/3 of the support at the bottom and 1/3 at the top. I also think you run into a connection issue by changing 'A'. I have a difficult time articulating it but when I see how you show 'A' I see a moment frame versus a truss. I would prefer to design a truss for stiffness to a moment frame.

Regarding reaction at the pivot bolt, which now seem somewhat irrelevant, I get

assuming 400lb rear wheel vertical
~462on shock (assuming 30 degrees from vertical connected just short of axle)
~pivot bolt 230lb pulling away, downforce dependent on more accurate measurements.

Removing that rear triangle as Jed suggests seems like a bad idea without some significant reinforcement to replace that support on the rear pivotbolt.

[jed.only]

The moment he said free-body diagram it was pretty obvious

And, pos I don't think the x-z axis is very important but it might be significant enough to justify the bracing at "A" being at an angle.

The headstock is a fairly rigid structure in torsion because of the three tubes spaced but you have 2/3 of the support at the bottom and 1/3 at the top. I also think you run into a connection issue by changing 'A'. I have a difficult time articulating it but when I see how you show 'A' I see a moment frame versus a truss. I would prefer to design a truss for stiffness to a moment frame.

Regarding reaction at the pivot bolt, which now seem somewhat irrelevant, I get

assuming 400lb rear wheel vertical
~462on shock (assuming 30 degrees from vertical connected just short of axle)
~pivot bolt 230lb pulling away, downforce dependent on more accurate measurements.

Removing that rear triangle as Jed suggests seems like a bad idea without some significant reinforcement to replace that support on the rear pivotbolt.

how would this reinforcement be accomplished? the support at the pivot bolt being structure holding or "pushing" the pivot forward to counteract the pivot wanting to pull out hte back of the frame?

[Dreef1999]

how would this reinforcement be accomplished? the support at the pivot bolt being structure holding or "pushing" the pivot forward to counteract the pivot wanting to pull out hte back of the frame?

I honestly think if you just want the 'look' that you wouldn't need much to do it now. If you want it to 'perform' then you won't be able achieve the same minimalist monoshock look you want.

The best I can think of is to chop the rear triangle near 'E' and weld some tube from the chopped 'E' to the top of the triangle now. You could incorporate it into your monoshock support which would give the metal some visual 'purpose'.

To really get much cleaner would involve a lot more welding I think.

A couple things of possible interest monoshock conversion showing the spot.

http://www.thegsresources.com/_forum/showpost.php?p=600184&postcount=332

Vintage racer from the same thread. Look close at what they did in the back. They went straight up from that 'E' point and attached the rear suspension.

http://www.thegsresources.com/_forum/showpost.php?p=500521&postcount=1

[midnightcafe]

Free Book!

So I just downloaded the Motorcycling chassis and suspension design book, and it is amazing. So much information! Very technical, an engineer would be able to fully appreciate it.

If you'd like a copy, let me know how I can send it (It's a 68.2mb file).

[posplayr]

Midnight

PM sent for the book.

JED,
maybe you should start another thread for your project . Be more clear about your objectives and maybe there might be some comments that will help you.
Pos

[tone]

okay, what if i did this:



cut off the brown part

Well ...... if you are fitting a monoshock swingarm all the tubes marked here are redundant so theres no real problem removing them, although you WILL need the aditional bracing as discussed here before plus a small plate at the juntion of the V from the seat rails to the diagonal down tube, ive done this quite a few times with no ill effect on the bikes handling

Moving on from that & getting a little more extreme i've also removed the rear tubes from under the tank & down near the swingarm pivot leaving just the main frame loop & braced/monoshocked as previously discussed also with no ill effects this is also where i would remove the tubes prior to converting to a hardtail chop frame

Hope that helps tone

[drhach]

So I just downloaded the Motorcycling chassis and suspension design book, and it is amazing. So much information! Very technical, an engineer would be able to fully appreciate it.

If you'd like a copy, let me know how I can send it (It's a 68.2mb file).

Tony Foale did a lot of hard work that all of us are reaping the rewards for. Please do not give away illegal copies of his copyrighted material. Generally I am not against this kind of thing. In this case, I spent the money on the book, I read it cover to cover. As an engineer I can really appreciate all of the work that he did and I think the man deserves to be compensated for it. Please, delete your offer.

[posplayr]

http://www.amazon.com/Motorcycle-Handling-Chassis-Design-science/dp/8493328634

I ordered it New from Amazon for $88 delivered.
also more infor here:

http://www.tonyfoale.com/

click on Articles:

Miscellaneous Articles.
THE CONTENT OF THESE ARTICLES REMAINS THE COPYRIGHT PROPERTY OF TONY FOALE. Reproduction for any commercial purpose whatsoever is strictly forbidden without the prior consent of the copyright holder. However, they may be freely downloaded, stored in computers and printed provided that such use is solely for the private enjoyment of those concerned.


The following articles were mostly written around the mid to late 80s. and discuss various aspects of Motorcycle handling, stability and future possibilities. They are presented here because many people have requested easy access to them, and are offered in the hope that they will be informative to read and stimulate further thought on the subject. Because of the nature of such articles the passage of time has not generally made the content obsolete. Small changes have been made to some of the original text to remove or replace untopical references, and improve clarity in some cases.

[posplayr]

http://www.tz350.net/book_reviews2.htm


Motorcycle Handling and Chassis Design, the art and science
By Tony Foale.
Until recently, Tony Foale’s original book “Motorcycle Chassis Design” ( co-written with the late Vic Willoughby ), has been regarded as somewhat of an industry standard in the field of motorcycling handling and chassis construction.
Tony’s latest offering “ Motorcycle Handling and Chassis Design, the art and science” has “raised the bar” and takes the reader to new levels of knowledge and education on the subject.


Thankfully, the author has chosen to pursue a more diagrammatic explanation of a lot of the theory involved, rather than clutter the book with too much hard to understand ( and sometimes boring ) mathematics.

This book is no light reading handbook, it’s actually quite an intense study of all the factors and physical forces in action during the motion of a motorcycle, though it's certainly not beyond the average technically minded enthusiast.

[zathros]

Tony Foale's disclaimer offers free access to the book as long as it is not for commercial purposes. He says it can be stored and freely enjoyed. I see nothing illegal when an author writes this type of disclaimer by someone sharing the file. He says it can be stored on a computer and freely downloaded. I don't believe Midnightcafe did anything illegal or unethical. He did not try and charge for a copy, no commercial gain, freely exchanged and freely downloaded. I believe the author's intent should be honored.


Miscellaneous Articles.
THE CONTENT OF THESE ARTICLES REMAINS THE COPYRIGHT PROPERTY OF TONY FOALE. Reproduction for any commercial purpose whatsoever is strictly forbidden without the prior consent of the copyright holder. However, they may be freely downloaded, stored in computers and printed provided that such use is solely for the private enjoyment of those concerned.


The following articles were mostly written around the mid to late 80s. and discuss various aspects of Motorcycle handling, stability and future possibilities. They are presented here because many people have requested easy access to them, and are offered in the hope that they will be informative to read and stimulate further thought on the subject. Because of the nature of such articles the passage of time has not generally made the content obsolete. Small changes have been made to some of the original text to remove or replace untopical references, and improve clarity in some cases.

[posplayr]

zathros

What I posted related to the articles on his website. As I dont have the pdf file, I dont know but would assume the same DOES NOT apply to the book sold on CD.

Do you know specifically what the copyright notice on the pdf says?