Jump to content

Top shock mount relocation


louie the fly

Recommended Posts

I've been scouring the archives for a while now and have decided that the top shock mount is the next job on the autumn/winter list. I have a couple of questions for those who have done it. Mines a 54 model Kingsway, like your Canadian models.

1. How long (typically) are the replacement shockers?

2. What part of the stroke should the shocker be in when the car is on it's wheels?

3. If anyone has a template or photo of a mount plate I'd appreciate it. This will tell me how vertical the shocker needs to be. I think the more vertical the more efficient it works, right?

Louie

Link to comment
Share on other sites

I am running Ford F1 mounts with Monroe 555004 shocks. Your mileage may vary on length. I had to go to the shocks I posted after putting in new springs in front.

The shock should ride in the middle of its travel. Basically between its compressed and extended length.

Here is a chart for shock length. travel, etc.

http://www.monroe.com/assets/downloads/english/08_MountingLengthSheet.pdf

Also a pic of the F1 mount I have on mine.

For a template try here.

http://www.jalopyjournal.com/forum/showthread.php?t=215548

post-7005-13585360318357_thumb.jpg

Edited by Alshere59
  • Like 1
Link to comment
Share on other sites

Hope it helped.

The only thing I would add to the HAMB article is the way the shocks are mounted to the new support. It looks like they just threaded a bolt through the support. The attachment point IMHO should more rigid. Looks like they tightened the bolt against the support with only the rubber grommet on the shock for tension. Also looking at the bolt in the picture its not a tight fit in the hole and will flex under load. Just my thoughts.

Link to comment
Share on other sites

Hope it helped.

The only thing I would add to the HAMB article is the way the shocks are mounted to the new support. It looks like they just threaded a bolt through the support. The attachment point IMHO should more rigid. Looks like they tightened the bolt against the support with only the rubber grommet on the shock for tension. Also looking at the bolt in the picture its not a tight fit in the hole and will flex under load. Just my thoughts.

That is/was my post on the HAMB.

I'm no engineer, and while I've had no problem with the 2 cars on which I did it that way, knowing what I do now I'd probably make the shock mounts a little thinner and use 2 per side with a space for the shock in between so they would be in what I think is called "Double shear".

Kinda like Pete & Jake's #1089 or #1081:

1081.jpg

Link to comment
Share on other sites

I am an engineering type of sorts but I'm always loath to reinvent the wheel (or the shocker mount). I like to see what others have done and what has worked for them. This is what I've come up with based on designs I've seen on the web.

I considered the deflection that could result under braking & cornering and decided it needed to be boxed. I did some tests with our software and it seems like the chassis may be the weakest point of the design now.

Now to get them cut and welded, then tack weld them on to the chassis.

post-7020-13585360372504_thumb.jpg

Link to comment
Share on other sites

Louie the Fly, it has been noted here on the forum that after welding the frame becomes the weak point around the weld area as it is small for the loads imposed on it. Some have formed a 3/16" or 1/4" plate to the contour of the frame area where the shock mount is to be located and welded it around its its edges to spread the load over a larger area of the frame. The plate is usually about 2"x2" or larger.

Link to comment
Share on other sites

Let's take a look at this from another perspective. If you can compress a shock with for discussions sake, 40 lbs of effort, how can it exert more that that force to a chassis component? And for non gas charged shocks most of us can easilly compress a shock by strength of arms only, how much force or weight is actually at work through a shock???

My basic instinct is that the shock itself ( unless it is a airshock, or a coilover style) does not support the weight of the axle, nor can it transfer more force than necessary to compress it despite the force that may be applied on it. It only damps the movement of the weight bearing assembly, unless the spring allows it to bottom out before the springs travel is complete.

So the shock in normal travel can only exert the amount of force necessary to move it through its compression and rebound cycle or from 40 to 150 lbs. I would think most are over built for normal applications and use, as the energy transferred is minimal compared to the effort transferred through the spring to the frame. And in the case of rear leaf springs all of that force goes through the spring shackle which look a lot more flimsy than most shock mounts.

Edited by greg g
Link to comment
Share on other sites

Greg;

I am in agreement with you that it is easy to compress a shock absorber. And the problem with extreme stress (weld failure) occurs when the shock bottoms out before the suspension does. It is easy to measure the travel in a shock absorber. But not so easy to measure suspension travel with the spring in place. Any ideas on how to take this measurement?

Link to comment
Share on other sites

Jack the car up and take a measurement from the lower A arm to a rreference point on the frame, then support the A arm and lower the car, adding weight as necessary to seat the A arm against the bump stop and then measure the travel.

Link to comment
Share on other sites

adding weight as necessary

Therin is the problem. How much weight would be required? If I stand my baloney a$$ on the bumper the car only drops an inch or so. I would guess it would take the entire starting lineup of the Steelers to squish the suspension completely.

Link to comment
Share on other sites

Was it this thread that blueskies offered to sell his shocks and frame mounts? I searched for his posting but did not find it. He may have deleted the posting as I bought them. So I will be doing this modification at some time in the future.

Don, I removed the post after you offered to buy...

Pete

Link to comment
Share on other sites

I also agree that a shock can be compressed fairly easily by arm strength. What I am not sure of is what happens when that compressing motion is much quicker than my arm motion. For instance over a dirt road or pothole riddled Pennsylvania highway? Only so much fluid can move through the valving in the shock during a given period of time. Could this not possibly cause momentary forces greatly larger than normal to be placed against the shock mounts? Not arguing here, just wondering out loud. I have seen some broken shock mounts that obviously I could not break with my arm strength. What do you guys think? Am I way off base in my thinking?.............Tim

Link to comment
Share on other sites

well here is one answer

All modern shock absorbers are velocity-sensitive -- the faster the suspension moves, the more resistance the shock absorber provides. This enables shocks to adjust to road conditions and to control all of the unwanted motions that can occur in a moving vehicle, including bounce, sway, brake dive and acceleration squat.

So in that situation the force transfered through the shock would increase proportionatly to the frequency of the cycle.

Link to comment
Share on other sites

Love this type of thread.

As posted earlier I replaced mine due to addition of new springs.

With that said I can only get 6.625 inches of travel with the shock I used.

With a ride height of 14.5 inches (measured between shock mounts) that left me with almost 4 inches travel down and roughly 2 + a bit inches up. With no spring my suspension traveled a lot more than any shock available could. There is just not enough travel. I did my purchase with a compromise. Then added a higher control arm bumper so that I had a half inch of rubber for the shock to bottom out before it reached its compressed length. Old dodge has a point, I have seen a few broken shock mounts but never on my vehicle. So whats the consensus. Shock bottoming or can't handle the stress of dampening the bump? I don't see a big issue with it extending. I have been wrong before.

With Hughforrests shock mounts I would probably weld the bolts making them studs. Should be the same as an F1 mount then. It looked good then and now just needs some more rigidity. IMHO. Is there anything to gain from a complete rework? Cant find any frame damage on the forum from welding the mounts but haven't been here long and no searches get me anywhere. So I can't speak to that at all.

Edited by Alshere59
Link to comment
Share on other sites

Wow, this is getting deep. I've decided to change my design a bit and go with a stem top mounting - either S1 or S3 as per the Monroe chart that was posted earlier. I'm not near the car at the moment so does anyone know what size the stock bottom mounting is? I suspect it is a 3/4" pin that the shocker mounts on. Can someone confirm this?

Link to comment
Share on other sites

Greg, velocity-sensitive is a great descriptor for what I was trying to describe. What I am getting at is if the ability of the fluid to escape through the valving quickly enough due to excessive compression velocity is exceeded momentarily the shock could become rigid for a moment. For that moment extreme forces would be placed on the mounts as well as the shock housing itself. The weakest link in the chain would eventually fail, probably a shock mount.

Alshere59, I always thought the mount breakage is most likely on the compression stroke of the shock due to the above description, but I also believe the most important function of the shock absorber is rebound dampening. The spring should control the compression of the suspension and the shock should control the rebound to normal ride height, Not enough rebound dampening and the suspension could theoretically over travel on the up stroke as well. Less likely though due to the weight of the vehicle. This would also use the shock mounts to stop travel. Like you, I love threads like this.............Tim

Link to comment
Share on other sites

Given our vehicle operational environments, is high velocity ocilations to the point of shock rigidity an issue? Corduroy washboard dirt roads come to mind as something I try to avoid, at least at speed.

I would think the ford or dodge pickup mounts are more than suffiecient for the way we use our vehicles. But that is why we have freedom of choice and miriad resources.

Link to comment
Share on other sites

Greg, I agree completely. Given the way I use my '41 I think any of the pictured mounts would work. I was talking only of theory and extreme conditions that could explain a broken shock mount and the reasoning behind what looks like over-engineering of a simple piece. Time to go dream of rebound dampening and compression. Good night guys.........Tim

Link to comment
Share on other sites

Wow, this is getting deep. I've decided to change my design a bit and go with a stem top mounting - either S1 or S3 as per the Monroe chart that was posted earlier. I'm not near the car at the moment so does anyone know what size the stock bottom mounting is? I suspect it is a 3/4" pin that the shocker mounts on. Can someone confirm this?

When you ask about the bottom mount for a 50 plymouth its an L1 or 5/8th. The rest are given in the earlier chart. You have two vehicles so not sure which you are asking about.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.

Terms of Use