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-   -   Front Coil Over Shocks on a Straight Axel! (http://www.hotrodders.com/forum/front-coil-over-shocks-straight-axel-229154.html)

Fe Block 02-03-2013 08:16 PM

Front Coil Over Shocks on a Straight Axel!
 
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It's not a topic with a lot of answers on this site, but I appreciate those who did give me feed back. I finished removing the single leaf and upgraded my Model A with front coil overs. I have added many details of the project to my photo journal and would be happy to expand the discussion if there are any specific questions.

RWENUTS 02-03-2013 10:18 PM

I can't tell in your photos, how did you mount a panhard bar?

jaw22w 02-04-2013 08:37 AM

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I have also eliminated the buggy spring on my '27 T. It makes the old roadster handle pretty well with 4 corner coil overs with 4 bar suspension front and rear. I think I see a panhard bar on your front end? What rate springs did you use? I used 225# springs. It may be just a little stiff, but handles well. My car weighs 1050# on the front What does yours weigh on the front? The front suspension was modeled after a pavement sprint car.

Fe Block 02-04-2013 03:11 PM

Front Coil Over Shocks on a Straight Axle!
 
5 Attachment(s)
The passenger axle mount shown painted red has a pan mount welded to it with two adjustment holes. The drop down mount on the driver's side is attached to the frame and the pan bar sits level right behind the front axle. This allows the bat wings to be free of any pressure and effectively attaches the pan bar to the front axle. Quarter inch angle iron with a quarter gusset and 3/16 tabs.

Fe Block 02-04-2013 03:24 PM

I am using a 175lb, 14" spring. My front weight was 1110 before this modification. Can't wait to feel what this suspension does. If the snow ever goes away! I like the looks of your front axle, nice engineering!

jaw22w 02-04-2013 04:40 PM

Thanks, but the engineering came from the sprint car. I just adapted it. Your car is only 60# heavier than mine on the front axle. Have you not tried it with the 175# springs yet? I am anxious to hear how it works on the street. I have been playing with the idea going lighter on my springs. I have 225# front and 150# rear. It is firm but not like a buckboard. Being from upstate NY, you are in the same boat as me as far as driving your hot rod until it warms up and the snow goes away

Fe Block 02-04-2013 07:18 PM

I am running #300 springs in the rear with a weight of 1680. They work great. The rear springs are shorter, 10" as compared to the 12" spring in the front (in the prior thread I stated 14" but that was wrong. 14" is the total length of the shock and spring). Just didn't have the room in the back for a longer shock (the back shocks sit 12" total) The longer the spring the less spring weight that is needed because more coils get involved. If I were using a 10" in the front I would move up to #185-200. You may have a stiffer spring than is needed at #225. I can't tell you how this rides yet......till I see some pavement Haha! (Upstate NY). Later, I'll put an update in my Journal on how the ride and handling goes. In the mean time....

Here is an online spring rate calculator you can play with. This should help. Spring Rate Calculator Ridetech News and Information

aosborn 02-04-2013 09:54 PM

Quote:

Originally Posted by Fe Block (Post 1642631)
The passenger axle mount shown painted red has a pan mount welded to it with two adjustment holes. The drop down mount on the driver's side is attached to the frame and the pan bar sits level right behind the front axle. This allows the bat wings to be free of any pressure and effectively attaches the pan bar to the front axle. Quarter inch angle iron with a quarter gusset and 3/16 tabs.

It is difficult to tell from the photo, but it appeatrs that the frame mount is simply butt welded to the bottom of the rail. If it is, you might want to consider gussets that come up the inside of the frame rail for strength. There is quite a bit of side load on a Panhard bar.

Regards,

Andy

jaw22w 02-05-2013 10:50 AM

My understanding of coil springs is that (as an example) a 300# spring will compress 1" with 300# on it, 2" with 600# on it, 3" with 900# on it, etc. regardless of the length of the spring.
I see from the calculator that going to a longer spring requires a lighter weight spring. I don't understand.

Fe Block 02-05-2013 03:32 PM

jaw22w

The more coils involved in a longer spring and shock the more vertical movement with the same impact. 10" spring moves 1" but a 12" will move 1 1/8" You use lessor weight spring but the additional movement results in the same weight after you multiply. 1 *300 or 1.125 * 275 roughly the same. I think that's how it works!!!!

Fe Block 02-05-2013 03:37 PM

It is a channel weld up one inch on both sides of the frame, BUT since the mount already has holes, and there is still a buggy spring pad on the cross frame, I could easily bolt a rigid diagonal brace from the middle of the pan mount up to the middle of the frame. Thanks for the feedback. Super Idea

aosborn 02-07-2013 07:18 PM

Quote:

Originally Posted by Fe Block (Post 1643054)
jaw22w

The more coils involved in a longer spring and shock the more vertical movement with the same impact. 10" spring moves 1" but a 12" will move 1 1/8" You use lessor weight spring but the additional movement results in the same weight after you multiply. 1 *300 or 1.125 * 275 roughly the same. I think that's how it works!!!!

That is not really how it works. I 300lb spring is a 300lb spring regardless if it is 2" or 12" long. One will just coil bind sooner than the other. 300lbs compress it one inch, 600lbs 2" etc, unless it is a progressive spring.

Regards,

Andy

jaw22w 02-07-2013 08:06 PM

[QUOTE=aosborn;1643896]That is not really how it works. I 300lb spring is a 300lb spring regardless if it is 2" or 12" long. One will just coil bind sooner than the other. 300lbs compress it one inch, 600lbs 2" etc, unless it is a progressive spring.

That is what I thought also. So why does the calculator posted above say you need a different spring when you change the length of the spring? I have been thinking about this for a couple of days. It has been bothering me. I have used coilover springs and shocks on race cars for over 20 years and I just don't understand why that calculator shows that.

aosborn 02-07-2013 10:36 PM

[quote=jaw22w;1643911]
Quote:

Originally Posted by aosborn (Post 1643896)
That is not really how it works. I 300lb spring is a 300lb spring regardless if it is 2" or 12" long. One will just coil bind sooner than the other. 300lbs compress it one inch, 600lbs 2" etc, unless it is a progressive spring.

That is what I thought also. So why does the calculator posted above say you need a different spring when you change the length of the spring? I have been thinking about this for a couple of days. It has been bothering me. I have used coilover springs and shocks on race cars for over 20 years and I just don't understand why that calculator shows that.

Are you referring to the pre-load setting they have shown? Since they are showing you three different spring choices you would need to preload each spring a different amount to support the car.

jaw22w 02-08-2013 06:51 AM

[quote=aosborn;1643941]
Quote:

Originally Posted by jaw22w (Post 1643911)

Are you referring to the pre-load setting they have shown? Since they are showing you three different spring choices you would need to preload each spring a different amount to support the car.

No, not referring to the preload. When I input the weights and angles for my car using a 6.3" travel shock and a 12" spring, performance mode recommends a 150# spring with .47 preload. Then when I input the same numbers but change to a 4.1" travel shock with a 10" spring, performance mode recommends a 200# spring with .52 preload. I don't understand why when changing spring lengths, the spring rate needs to change.


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