Suicide front suspension

[Sixx]

Ok, I'm being a dork...does anybody have any photos of how they built a suicide front suspension on a 1930's frame?? I'm working on Revell's '30 model A coupe, & would like to do that on it. Thanks for any help...?

[Ace-Garageguy]

I usually use a tubular front crossmember, and fab the perch itself out of sheet stock. 

Model T frame below:

'32 Ford Frame below: 

[Ace-Garageguy]

Using channel stock works very well too.

 Here I've started making the perch up from 2 sections of styrene channel. I left the forward leg long to get a good idea of the alignment of the perch with the frame rails. I like things that are square and symmetrical.

In this shot, the perch has been trimmed to its final configuration. The mount pad is 1.7mm higher than the tops of the frame rails, which is what that earlier figuring told me I'd need.

[Sixx]

Ha...how funny is that?! I had found your first pic on the "net" somewhere and have been staring at it for awhile now!! Man, thank you bigtime for your help! Your photos will go a long way in helping me!!!! Thanks! ?

[Ace-Garageguy]

Glad you found it useful.  

I recommend careful mocking-up to determine your exact ride height to get the stance and proportions you want, first.

I wanted to go quite low with this one, but I didn't want an excessively tall perch in front of the radiator shell for aesthetic and functional reasons (a very high perch can tend to flex, and is more likely to fail...hence "suicide" mode).

I ended up needing to zee the front rails to get the perch to be a reasonable height.

Then, after the new tubular crossmember was in, it was easy to mock up the frame, and establish the exact final height of the perch...which will be fabricated as in the previous examples.

 

Edited June 14, 2018 by Ace-Garageguy

[OldNYJim]

I LOVE seeing your work, Bill.  That one in the post above is AWESOME - is there a build thread for that somewhere?

[Ace-Garageguy]

2 hours ago, CabDriver said:

I LOVE seeing your work, Bill.  That one in the post above is AWESOME - is there a build thread for that somewhere?

Thank you sir. 

Build thread here:

 

[Greg Myers]

Okay, that was the easy part. 

Now where do you come up with all those extra radius rods? 

[Ace-Garageguy]

12 minutes ago, Greg Myers said:

...Now where do you come up with all those extra radius rods? 

One thing that makes this such a great kit is that it has hairpins AND a 4-link setup:   (Only Revell '32 Ford with BOTH)

And another reason why the hobby really needs a repop of this fantastic parts source:   

[Lunajammer]

Looks like I've got another Engwer bookmark.

I'd like to try one of these set ups, even though I can't understand why any hot rodder would think a suicide perch is a good idea. It just looks like it has catastrophe written all over it.

[Greg Myers]

Thus the name "Suicide Front End" although I've never heard or seen one fail not even on some shoddy rat rat rod.

[Greg Myers]

And another reason why the hobby really needs a repop of this fantastic parts source:  Yes indeed. 

[Ace-Garageguy]

1 hour ago, Lunajammer said:

...I can't understand why any hot rodder would think a suicide perch is a good idea. It just looks like it has catastrophe written all over it.

 It's just a way to get a look and stance that's not available with any other setup.

And as long as it's designed and fabbed correctly, it's perfectly adequate.

Things to remember:

1) A round tubular front crossmember works best. Round tube is more torsionally rigid than rectangular or square, and that's important because the thing is trying to twist.

2) The front of the frame rails should be boxed where the crossmember ties in, at least. The rails should also be capped. Ideally, the crossmember should go through the rails and be welded at both the inner and outer intersections. More work, but if overkill is a good idea anywhere, this is the place.

3) The perch itself needs to be fabbed from heavy enough material (3/16" -1/4" steel plate is about right) and the welds need to be good. Good welds means the material is well-cleaned of rust and mill-scale prior to welding, and that penetration is excellent and consistent.

4) The spring mount plate needs to have vertical reinforcing ears or gussets to keep it from twisting off the crossmember as well.

So...the example below is not what you want to end up with.

The example below has adequate perch and crossmember work, but placing the spring end hangers that way, into the sides of old wishbones, is a little scary. Wishbones were never intended to be loaded that way, and I HAVE seen them fail in a rig like this.

 

Edited June 15, 2018 by Ace-Garageguy

[Jantrix]

35 minutes ago, Ace-Garageguy said:

The example below has adequate perch and crossmember work, but placing the spring end hangers that way, into the sides of old wishbones, is a little scary. Wishbones were never intended to be loaded that way, and I HAVE seen them fail in a rig like this.

 

This saves me another of my "what's Bill think of this?" PM's. I've been seeing this a lot on my Google searches.

[Ace-Garageguy]

9 hours ago, Jantrix said:

This saves me another of my "what's Bill think of this?" PM's. I've been seeing this a lot on my Google searches.

 There are a couple of caveats here too.

1) IF the ends of the wishbones where the hangers go through them were re-fabbed from heavier stock, things would be much better...but trusting old parts, possibly rusted internally (wishbones are tubular in this area), especially where the ends are loaded in bending and subject to fatigue-inducing vibration and bumps from road irregularities, is unwise.

2) The spring-end hangers are also loaded in a way they were not designed to be. As designed, they're supposed to be in bending and tension or compression, but in the illustration above, the weakest part of the hanger is loaded in bending and single-shear. In general, loading anything in single-shear should be avoided. Though they are forgings, there is a stress-riser where the shank intersects the head. This is a prime potential failure point. And some aftermarket end-hangers are cast garbage...truly potential "suicide" parts if mounted this way.

IF the hangers were fabbed from known-quality forgings of the right material, and IF careful attention was placed on the fillet radius where the shank meets the head, and IF the wishbone was relieved to clear the fillet and allow sufficient clamping pressure to be applied by the threaded end, you could make a case for this to be an adequate design as well.

Edited June 16, 2018 by Ace-Garageguy

[Jantrix]

I spotted this one on the HAMb recently. It makes use of the stock spring location while pushing the axle forward. I just think that little weld area on the wish bones seems like a risk. The whole weight of the vehicle on those welds. I have seen others that are through bolted, which opens up other concerns.

This one seems sturdier.

Edited June 15, 2018 by Jantrix

[Ace-Garageguy]

I'm not seeing the other photo, but there are several significant problems with this one.

1) The front crossmember is rectangular, and it's not very large. It will be prone to twisting..

2) The length the perch is cantilevered forward of the crossmember is excessive, and will add to the tendency of the crossmember to twist.

3) The ears or gussets on the perch are not tall enough or placed correctly to provide sufficient rigidity either.

4) This mess also loads the end hangers and wishbones in a way they were not designed to be loaded.

I'm sure whoever built this garbage thinks they're pretty clever. They're not.

[Greg Myers]

Now if there was only a way to easily fab some radius rods, seems a shame to rob them from another kit.

[Ace-Garageguy]

4 hours ago, Greg Myers said:

Now if there was only a way to easily fab some radius rods, seems a shame to rob them from another kit.

It's really not hard to fab hairpins from .040" brass wire (for 1/25 scale). Use sheet plastic or brass for the batwings, and the end hardware can be made from commercial bolt-heads. You just have to understand what you're making, how it works, and separate it into simple shapes.

       

Older-style radius rods, like OEM-style "split wishbones" are also relatively simple shapes to fab from styrene stock.