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  #21  
Old 02-28-2014, 01:24 PM
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mainly for the look,it's styled after Miller Indy cars from the 30's-40's.
I have built two "lakes modified roadsters" using 1/4 elliptical springs.The first one used a radius rod and 1/4 E spring at the front and rear. The second one I
used 2 1/4 E's at each wheel.
I have talked to the owner of #1 and he said the car handles like a go cart.
That car uses utility trailer springs cut in half and a adjustable clamp.

Fred
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  #22  
Old 02-28-2014, 01:40 PM
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Ok, I'm going to stay with:
Divide by two, then by two per corner will get you in the ballpark.

I'm digging the concept and the looks but thinking that I would definitely build the lower spring with most of the rate and have it act like the Rad-Rod for handling. Since you are Street/lakes driving I'm wondering if you can clamp the lower spring at both the frame and axle, to cut down on the spring wrap and axle movement?

Pix? of the previous builds?

E
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  #23  
Old 02-28-2014, 02:44 PM
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I'll try to send you to my photo bucket page.

http://s210.photobucket.com/user/lak...?sort=3&page=1

This should be the "first one"

When you are done click on "third one"

When done click on OWNER-PC and go way down tell you see the second one.

Fred
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  #24  
Old 02-28-2014, 05:38 PM
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Looks to me like you have it sorted!


E
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  #25  
Old 02-28-2014, 09:58 PM
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Quote:
Originally Posted by entropy View Post
Looks to me like you have it sorted!


E
Think I have to agree... screw the physics .. if it breaks go to plan 'B' hehe

Fred .. I browsed your pix.. I gotta say awesome, old school, well done..

I also liked the, I think ' knucklehead ape hanger ' but correct me if wrong...

r'z .. have a good weekend...

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  #26  
Old 03-01-2014, 10:34 AM
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Thanks to all for the information you gave.
Entropy I wish the bike was a Knucklehead but it's just a "Ironhead" Sportster.

Fred
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  #27  
Old 03-04-2014, 02:17 AM
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Entropy I wish the bike was a Knucklehead but it's just a "Ironhead" Sportster.

Fred
Although Entropy guest wrong.. LOL .. and Harley having giving more head than I've gottin' .. .. I do agree .. you have it handled. and if not .. always a plan B..

With respect ....

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  #28  
Old 03-06-2014, 11:36 AM
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I found this on Pirate4X4.com

I'm not questioning the knowledge here, just wondering what the tech behind it is
the moment of a simple span beam (your leafspring, L inches long) with a load in the middle (your axle, P) is PL/4

the moment for a cantilever beam with the load at the end is PL

so if you cut the spring in half, use it as a 1/4 eliptic, you should be doubling the spring rate.

I could have missed something, that's a gross simpification, but I think it'll get you in the ballpark.
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  #29  
Old 03-06-2014, 05:43 PM
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I think for what you are doing that dividing the calculated spring rate for a semi-elliptical (typical leaf spring) in half will be in the ball park for a 1/4-elliptical. which is why I said divide by 2 then divide by 2 for your application of two springs...

E
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  #30  
Old 03-06-2014, 07:46 PM
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entropy
I'm slow so bear with me here.
The springs are 1000# for the pair.
So 500# each.
I cut them in half and divide by 2 = 250# each.
Now you said to divide by 2 again making each spring 125# ?
Hope you go along with "there is no dumb questions" cuz I'm feeling
a little dumb right now.

Fred
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  #31  
Old 03-06-2014, 11:08 PM
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Quote:
Originally Posted by lakesmod View Post
entropy
I'm slow so bear with me here.
The springs are 1000# for the pair.
So 500# each.
I cut them in half and divide by 2 = 250# each.
Now you said to divide by 2 again making each spring 125# ?
Hope you go along with "there is no dumb questions" cuz I'm feeling
a little dumb right now.

Fred
If a spring pack (typical leaf spring) has a 1000#Rate.
If you cut it in half then 1/2 the above is 500#Rate
You want to use two (upper and lower) 1/4-Eliptic springs so you would need to achieve 250# for each if you want a 500#Rate...
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  #32  
Old 03-06-2014, 11:29 PM
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Do you have a photo or link showing the type of suspension arrangement you're going for? Also do you know your front and rear weights? I can help with the right info.
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  #33  
Old 03-07-2014, 01:04 AM
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Pictures here

<a href="http://s210.photobucket.com/user/lakesmod/media/First%20one/hpcomputerpictures050.jpg.html" target="_blank"><img src="http://i210.photobucket.com/albums/bb166/lakesmod/First%20one/hpcomputerpictures050.jpg" border="0" alt=" photo hpcomputerpictures050.jpg"/></a>

and



I think the weight will be about the same front to rear with a total weight of 2200# to 2400#.

Thanks Fred

Last edited by lakesmod; 03-07-2014 at 01:06 AM.
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  #34  
Old 03-07-2014, 06:22 AM
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<a href="http://s210.photobucket.com/user/lakesmod/media/First%20one/hpcomputerpictures050.jpg.html" target="_blank"><img src="http://i210.photobucket.com/albums/bb166/lakesmod/First%20one/hpcomputerpictures050.jpg" border="0" alt=" photo hpcomputerpictures050.jpg"/></a>

<a href="http://s210.photobucket.com/user/lakesmod/media/2014-01-29232826_zps47237cd2.jpg.html" target="_blank"><img src="http://i210.photobucket.com/albums/bb166/lakesmod/2014-01-29232826_zps47237cd2.jpg" border="0" alt=" photo 2014-01-29232826_zps47237cd2.jpg"/></a>

Fred
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  #35  
Old 03-07-2014, 11:16 AM
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Quote:
<a href="http://s210.photobucket.com/user/lakesmod/media/First%20one/hpcomputerpictures050.jpg.html" target="_blank"><img src="http://i210.photobucket.com/albums/bb166/lakesmod/First%20one/hpcomputerpictures050.jpg" border="0" alt=" photo hpcomputerpictures050.jpg"/></a>

<a href="http://s210.photobucket.com/user/lakesmod/media/First%20one/hpcomputerpictures050.jpg.html" target="_blank"><img src="http://i210.photobucket.com/albums/bb166/lakesmod/First%20one/hpcomputerpictures050.jpg" border="0" alt=" photo hpcomputerpictures050.jpg"/></a>

<a href="http://s210.photobucket.com/user/lakesmod/media/2014-01-29232826_zps47237cd2.jpg.html" target="_blank"><img src="http://i210.photobucket.com/albums/bb166/lakesmod/2014-01-29232826_zps47237cd2.jpg" border="0" alt=" photo 2014-01-29232826_zps47237cd2.jpg"/></a>
The pics are missing for me on the previous two posts. I can see the second pic of the first post of the two previous posts.

Richard
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  #36  
Old 03-07-2014, 11:26 AM
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[IMG][/IMG]

This is the front view.
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  #37  
Old 03-07-2014, 11:33 AM
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[IMG][/IMG]

This will be on all four corners.
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  #38  
Old 03-09-2014, 10:41 AM
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Another picture

[IMG][/IMG]
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  #39  
Old 03-10-2014, 12:51 AM
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coming along awesome.. something to see this up close and personal one day ...

Dog..............
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Last edited by FrogDog; 03-10-2014 at 10:24 AM. Reason: Cause I Can
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  #40  
Old 03-10-2014, 12:23 PM
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Quote:
Originally Posted by lakesmod View Post
I am cutting a lief spring in half to make a 1/4 elliptical spring.
The lief spring is rated @ 1000 lbs. Buy cutting it in half will the 1/4 spring be rated @ 2000 lbs since it is shorter therefor stronger?
The original rate of the spring was 500lb/in. The new rate for each spring half is 250lb/in. When you use two halves as you've shown above, the combined rate will be 500lb/in (as if you hadn't cut the spring at all). All you are effectively doing by cutting the spring is rearranging it. Also important to note is that your suspension geometry produces a motion ratio of 1 since the tire moves with the end of the spring (as opposed to on a control arm where the spring moves less than the tire).

For your 2,400lb vehicle, this is a fairly high spring rate. What I'm about to type up is based on handling theory (specifically ride frequencies) and some rules of thumb. For more info read these articles: http://www.rqriley.com/suspensn.htm, http://www.optimumg.com/docs/Springs...Tech_Tip_1.pdf

Let's assume the vehicle weighs 2,400lb and has near perfect weight distribution, so 600lb on each wheel. With a 500lb/in rate, your ride frequency is around 172CPM or 2.8hz. That is pretty dang stiff.

Here are some typical ranges I have read in literature:
Passenger cars: 30-90CPM (0.5-1.5hz)
Performance/racing: 90-120CPM (1.5-2.0hz)

I don't know if you're racing or cruising or both, but I'll suggest you are building a performance-minded vehicle and have some tolerance for a rough/stiff ride and want to target around 120CPM or 2hz. Again assuming 600lb on each wheel, to get 120CPM you would need a spring rate of a mere 250lb/in.. You can obtain this by cutting a 250lb/in leaf spring in half and using both halves.

Furthermore, you may want to design your suspension for a "flat ride" response. The idea of this is to make the rear suspension stiffer so that after your front hits a bump, the rear can bounce faster when it hits the bump so it can catch up with the front and the vehicle pitches less. A decent rule of thumb that I've heard is around a 10% different in front to rear, so in your case you could do 225F/250R or 250F/275R.
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Last edited by TheBandit; 03-10-2014 at 01:15 PM.
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