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Software request. for all you engineers


Guest Thurem

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Hey I need a program that will show me how a linkage(ie arrangement of arms and levers and how they interact) for a suspensiondesign will work. It needs to not be confined to a specific sort of suspension type. It only needs to be 2 dimensional. Free is the best kind. I'm trying to design this type of front suspension for a trike

http://hem.passagen.se/trike/ramarfoto.htm With two arms holding the fork part up by the steering head, and I wanna be able to control the suspension motion of the front wheel.

Obviously I come to this group of fine people cause they have so far been the most resourcefull group around.

Thanks in advance.

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I don't know of any mainstream programs that simulate various suspension types, but i do have a book that may (or may not) you in your search. Its called Chassis Engineering; it shows you how to build a suspension (for cars) from the ground up.

 

Since you're already designing a suspension, this book might be too on the newb side for u :-D .

 

Oh, and another thing. You might wanna try roughly drawing out your parts on Solidworks. Then you can see in 3D how each part interacts when assembled.

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Guest Nic-Rebel450CA

I can probably do this for you. I have experience coding in Java. This would be kind of a new area for me as I typically do work on GUIs (Graphical User Interfaces) for programs. If anyone offers to help that already has experience in this design area, I'd say probably go with them. If not, I am sure I could figure out such a design. The cost would depend primarily on how quickly you need it done. If you need it done promptly, free wont really be an option. If you have plenty of time, I am sure we could figure something out on the pizza and beer scale or similar. :wink:

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Pbooty, I guess this question would have never come up if I didn't allready sleep with that book under my pillow.

 

Smooth, 3D Studio Max is like 650bucks, does not qualify for the free part. I appreciate the tip though.

 

Nic, I am working out the program parameters, and will email them to you, and post them here.

 

Thanks for your input so far guys.

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Input for the program is: Location of points B,C,E,D Length of line EA.

 

conditions: Points B and C are fixed pivot points, D and E are also pivot points. The legnth of the lines do not change as the program

executes only the location of points A,D and E

 

Output for the program is: length of lines BD and CE distance between D and E, distance between D and C. Program should loop through 1 degree movements of line BD pivoting around point B, for 45 degrees.

User promt for each degree. redraw for each loop, draw a line for the movement of point A. calculate and display the distance that A

has traveled for the x coordinate and the y and the actual distance, redisplay the distance between D and E for each loop.

 

I think that covers it... :-D

 

album_pic.php?pic_id=2827

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if u r going to use finite element programs like this, u might want to double/tripple check the calculations. I've used finite element programs like Ansys and it overestimates results like stresses, strains, ect..

 

since suspension is kinda important, good numbers might make a difference :shock:

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Working model and/or working model 3D is the software you are looking for... Lets you design mechanisms: cams, linkages, spring & damper systems, etc., apply forces and accelerations and outputs whatever data you require. They are both fairly user friendly too. (well, if you are an egghead I suppose)

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Pro/E (Pro Engineer) isn't for the inexperienced... I've used it quite a lot and it's not-so-intuative to learn.

 

If you are looking for something more flexable than WM I'd look for Solidworks with the dynamic designer plug-in, but again it's way more program than you need for this type of thing. Working Model is the way to go I think.

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Working model is definatly the way to go, from my mechanical engineering school days I have a demo copy of working model 2d. I'm not sure if you can find one online, PM me if you can't.

 

Oh, also have a copy of solidedge (with dynamic designer) on cd, it stopped working about a year ago and I havn't tried to make it work since then.

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I downloaded a demo of Working Model 2d, and yes I will need to spend some time to unlock it's mysteries.

It looks like it will work for me and do way more than what I wanted, but thats cool too.

Thanks everybody

Thure

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Hey, it is now obvious to me that I wanted to be able to make a computer simulation of what was going on cause I didn't fully understand how this would work. Now that I've figured that out, here it is.

album_pic.php?pic_id=2832

It is all about the instant center, created by the links that control the fork. If the links actually connected to this instant center (ic) the fork would just pivot around the instant center. But, since the links are way shorter the ic will change with the movement of the fork. If the setup is designed so the ic is somewhere below and behind the front axle, you will get a desirable movement of the front fork. You can also determine how the shock/spring is gonna work this way, with this formula I came up with. wheel-springrate= Springrate * cos(shock angle) * Pic/Aic Where Pic and Aic is the distance from ic. If the links are positioned in a way so the relationship Pic/Aic becomes numerically bigger you will have a progressive wheel-springrate.

The next problem is to make sure the trail does not go away or become negative when a bump is encountered, this could make it unstable when hitting a bump, which would be bad...

This is somewhat simplified but it gives youa really good idea of what is going on.

Thure

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