Steering, Suspension, & Brakes

tips, technology, tools and techniques related to non-driveline mechanical components

Go to Thread: PreviousNext
Go to: Forum ListMessage ListNew TopicLog In


MGB-FV8
Jacques Mathieu
Alexandria, VA
(299 posts)

Registered:
09/11/2009 08:55PM

Main British Car:
1977 MGB Small Block Ford, 331 Stroker

Help needed for composite leaf spring problem solving.......
Posted by: MGB-FV8
Date: January 22, 2011 06:35PM

Hi, when I started the design of my MGB V8 project I decided to go with the light weight composite system offered by Doug Jackson. Jim Stuart has successfully ran the system on his yellow GT. I raised Jim’s car on my lift to take a look at the system and to see how it held together after five years on the street. Jim’s engine is a build up Buick 300 with a mild cam that makes decent power; I figure that the Doug Jackson’s system would also handle my Ford 331 stroker, and at the time, no one offered a 3 or 4 links system.

After inquiring with Doug Jackson about the rumors, he made it clear that I why he insisted on me purchasing the tramp bars with the springs because of the torque generated by the Ford small block 331. This is my fifth year working (seems like a life time) on finishing this project. The Doug Jackson springs were installed on the first year.

Since then, I had some people tell me that the springs would not withstand the high torque of the 331 and delaminate. It was pretty disappointing to hear after spending and installing the composite system. I contacted other people (including Jim) that had used them and all stated that anyone that had problem did not use the tramp bars.

As a safety measure, I wanted to install (along with the tramp bars?) a device similar to the one shown in the two pictures that James Bowler uses on his racing 1969 GT race car.
Understanding old school fundamentals, my question is “how can James Bowler’s top strut rod design allow the driveshaft yoke to slip in and out with leaf springs travel?” I can see how a 3-4 links system don’t generate as much yoke travel by using the coil-over spring suspension, but, a leaf spring works on stretching in and out on travel. I can only figure out that it is why he does not use lower tramp bars. It would seem like his design would allow for more leaf springs stretch from both sides of the axle tube.

Can someone kindly help me through this geometry puzzle? I sure don’t want to shred the springs; my other option is to take them off, sell them, and go with a link set up. That would be pretty costly; the last 2 pictures with the pinion mounted parking brake are mine, thanks.

Jacques
JamesBowler-DE.jpg
JamesBowler-DF2.jpg
Latest MGB pics February 2010 007.jpg
Latest MGB pics February 2010 010.jpg


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1087 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Help needed for composite leaf spring problem solving.......
Posted by: ex-tyke
Date: January 23, 2011 09:25AM

Maybe I'm missing something here, but the D/L slip yoke is at the xsmn not at the RA.
Jim's upper link effectively prevents RA rotation/spring windup - it shouldn't have an effect on D/L slip joint operation.


tr6turbo
Dale Knapke
Sidney, Ohio
(165 posts)

Registered:
08/24/2008 09:44PM

Main British Car:
1972 Triumph TR6 Ford 2300, 4 Cyl Turbo

Re: Help needed for composite leaf spring problem solving.......
Posted by: tr6turbo
Date: January 23, 2011 10:33AM

It seems to me that the leaf springs act like lower links in a 3 link. Any change of length in the lower link would be small and should not be a problem for the slip joint.


MGB-FV8
Jacques Mathieu
Alexandria, VA
(299 posts)

Registered:
09/11/2009 08:55PM

Main British Car:
1977 MGB Small Block Ford, 331 Stroker

Re: Help needed for composite leaf spring problem solving.......
Posted by: MGB-FV8
Date: January 23, 2011 05:14PM

As far as the leaf springs are concerned, I was always told that just like a bow being pulled and release it will make its length vary between pull and release. If you raise your car up on a hoist (which we do at work all the time), as the wheels come off the ground, you can watch the slip yoke slip back a bit from the tranny (or slip spline if equipped).

Anyone that has ever installed tramp bars has felt a change in the ride. Basically, the portion of the spring that has the tramp bar mounted directly underneath cannot move. This is why they sell “Slide-A-Links” for street ride. [www.competitionengineering.com]

The rear portion of the leaf spring is the one that has to flex back and forth, this is why you have a shackle. Link system operates differently with full coil over spring function to dampen the suspension.

Independent suspension is the ultimate, it keeps the rear differential in a fixed position, and hence, yoke slip is almost eliminated, although it’s not spared from wheel hop. This is why, I assume that the top strut bar used on Bowler’s car would eliminate the need for the lower tramp bars, hence, restore full leaf spring action.

I know that Ted Lathrop does not write on this forum but when I asked him about the tramp bars causing spring limitation, he seemed to agree with me in principle.

I know that spring/axle wrap is control by the tramp bars but causes limitations. Hopefully, someone can shine some light on the top strut rod advantage versus tramp bars. I’m trying to improve the ride by allowing the full spring to work, how much does it restrict spring efficiency?


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1087 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Help needed for composite leaf spring problem solving.......
Posted by: ex-tyke
Date: January 23, 2011 08:43PM

Jacques, I'm of the opinion that if the upper link is in place, then the tramp bars become redundant.
I've never been a fan of anti-tramp/traction bars or whatever you want to call them....they should be confined to the drag strip!
As Ted has confirmed, they compromise rear leaf articulation and effectiveness. Given the fact that you are using composite springs, your money would be better spent on a Panhard rod as the composite spring cross section doesn't lend itself to the lateral loading ability (stiffness) of a multi leaf steel spring assembly.
......my .02 cents.


MGB-FV8
Jacques Mathieu
Alexandria, VA
(299 posts)

Registered:
09/11/2009 08:55PM

Main British Car:
1977 MGB Small Block Ford, 331 Stroker

Re: Help needed for composite leaf spring problem solving.......
Posted by: MGB-FV8
Date: January 23, 2011 09:20PM

Thanks Graham, as far as the Panhard rod goes, I believe that I already have something better in place a "Watts linkage". If you look at the third photos above, you'll see above the pinion something that looks like a set of ears with arms attached to it. That's my Watts linkage. It came as an option with the pinion mounted parking brake kit. [www.tsmmfg.com]

When I spoke to the salesman at TSM about it, he stated that it was designed for street rod with narrow frame rails, so I and also he thought that it may be a good substitute to the Panhard rod.

Since I'm such a glutton for punishment, and also since I'm still in the fabrication mode, I think that I'm going to weld provisions for this top strut rod and leave the rod off. This way, when or if the car ever sees pavement, I can disconnect the tramp bars and hook the top strut rod. It'll give me (and others) a test subject to go by.

I thought for sure that more members would have chimed in on this thread since there are so many improvements to be made to the stock suspension, IMHO.

BTW Graham, my brother (in Canada) loves your car; he thinks that it is one of the cleanest jobs on this site.

Jacques


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1087 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Help needed for composite leaf spring problem solving.......
Posted by: ex-tyke
Date: January 23, 2011 11:14PM

Quote:
I thought for sure that more members would have chimed in on this thread since there are so many improvements to be made to the stock suspension, IMHO

I agree!... and one of the reasons why some folks opt for composite springs, tube shocks, IRS derivatives or a 3-link/panhard and why I chose a 4-link.

Thanks for the accolades on my conversion - your brother must have good taste.



roverman
Art Gertz
Winchester, CA.
(3006 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Help needed for composite leaf spring problem solving.......
Posted by: roverman
Date: January 29, 2011 09:11PM

Clan, 3 or 4 bar set-ups, with or with-out lateral control, other than leafs or triangulated upper bars, should consider "floating" the the leafs. This will relieve them of any loads other than weight.For "independant types", I suggest a study of the Corvette, tranverse , composite monoleaf system. Because of clever "pick-up points", they reduce roll , by virtue of "S wave", under cornering loads.Cheers, roverman.


MGB-FV8
Jacques Mathieu
Alexandria, VA
(299 posts)

Registered:
09/11/2009 08:55PM

Main British Car:
1977 MGB Small Block Ford, 331 Stroker

Re: Help needed for composite leaf spring problem solving.......
Posted by: MGB-FV8
Date: January 29, 2011 11:22PM

Art, thanks for chiming in; they only Corvette transverse springs that I'm familiar with are attached at each end via drop links; something like swaybar end links (see photo: [www.corvettefever.com] ) which allows the springs to stretch in and out. Isn’t "S wave" action subject to breaking springs? It also seems like it would cause unforeseen reactions just like spring wrap.

My 2 cents


roverman
Art Gertz
Winchester, CA.
(3006 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: Help needed for composite leaf spring problem solving.......
Posted by: roverman
Date: January 31, 2011 07:46PM

Jacques, picture appears to be 83' and prior ? Vette started with composite monoleafs,front/back in 84'? As I said, Vette takes advantage of "s wave", in these springs to reduce roll. Millions of Vettes, have been using this system since 84', and no "Ralph Nader" yet. Cheers, roverman.


Sorry, only registered users may post in this forum.