satchel link in 65 mustang

[thinkfastroth]

I would like to angle the lower links in towards the axle. Do the angles need to be at 40* or can it be greater say 50 or 60?
Thank for all advice.

[Norm Peterson]

What are you referencing those angles to?

Versions of the triangulated 4-link (of which the Satchell Link is a named variation) tend to run the links that are primarily responsible for axle lateral location somewhere between 30° and 45° as measured from vehicle centerline. The Fox/SN95 Mustangs (uppers) are closer to 30°, and most GM uppers are around 45°.

It sounds like you want to use the existing chassis brackets and have the LCA axle side pickups close to the pumpkin. That won't support the axle ends against acceleration and braking loads anywhere near as well as leaving the LCA axle side pickups out near the axle ends and inclining the LCAs inward going to the chassis (this being the "real" Satchell configuration, which necessitates some additional chassis structure and some complication in the vicinity of the driveshaft). I'm a little concerned that axle tubes not supported out near their ends will bend slightly, giving you rear toe changes under load.

Keep in mind that every OE stick axle link-type rear suspension attaches the lower links to the axle tubes out as far toward the axle ends as practical.


Norm

[thinkfastroth]

What are you referencing those angles to?

Versions of the triangulated 4-link (of which the Satchell Link is a named variation) tend to run the links that are primarily responsible for axle lateral location somewhere between 30° and 45° as measured from vehicle centerline. The Fox/SN95 Mustangs (uppers) are closer to 30°, and most GM uppers are around 45°.

It sounds like you want to use the existing chassis brackets and have the LCA axle side pickups close to the pumpkin. That won't support the axle ends against acceleration and braking loads anywhere near as well as leaving the LCA axle side pickups out near the axle ends and inclining the LCAs inward going to the chassis (this being the "real" Satchell configuration, which necessitates some additional chassis structure and some complication in the vicinity of the driveshaft). I'm a little concerned that axle tubes not supported out near their ends will bend slightly, giving you rear toe changes under load.

Keep in mind that every OE stick axle link-type rear suspension attaches the lower links to the axle tubes out as far toward the axle ends as practical.


Norm

Norm,
I have a design that I have come up with using the 4barlinkV3.1 but I cant convert it to post.
are you familiar with the program and know how to get it to post?

[Norm Peterson]

Sorry, I'm not familiar with that one. What I've done is write Excel spreadsheets that accomplish pretty much the same thing (the geometric constructions are reasonably simple).

If you could post (or PM, if you prefer) the X, Y, and Z coordinates of the various pivot points I ought to be able to come up with something. It's time I added an option or two to the triangulated 4-link sheet that's already in the 3-link sheets (things that I'm too lazy to do without a specific reason). It'll come out looking sort of like this except the curves would of course be different (that one happens to be for an '08 Mustang 3-link/PHB mostly because it was handy). Quite a variety of curve shapes are possible for antisquat.

51589

One thing you might be able to do is copy a screenshot to anything that will save a .jpg, and then upload the picture. That'd at least present whatever inputs and outputs it works with.


Norm

[thinkfastroth]

Norm i hope this helps.
Uper links x y z
frame 27 16 16.5
axle 0 16 16.5

lower links
frame 26 16 8
axle 0 3 6.25

This is what i would like to use buti'm under the impression that I might need to move the lowerlinks back to get the proper angle. I'm planing on instaling a crossmember in to attcah mounts on.
Thank you for your time and help

Jerred

[Norm Peterson]

Quick and dirty - that looks like about 26.5°, which means that the lower link forces just from cornering are going to get rather large. I'll try yo get a pic up tomorrow AM.


Norm

[Norm Peterson]

Here's what I get as a function of ride height for those numbers. I assumed a 108" wheelbase, 21" CG height and a 0.3" drop in ride height for when the driver gets in. I didn't get around to updating the sheet yet, but what there is in it is still OK

51614


Rollsteer looks good, if a little low for relaxed driving (tinkering with the UCA side view inclination can fix this).

But the anti-squat as a function of ride height is more or less opposite to what I think you'd want. Instead of planting the tires a little harder as the car squats, it plants them a little less hard and will be more likely to give you wheelspin or even hop. I think if the uppers were about 10" long you'd be much better off from a launch traction point of view - and without driving the anti-squat excessively high either. Something like

51618


But attaching the axle side of the lowers inboard toward the pumpkin still makes me uneasy. There will be a total longitudinal force that'll be about double the tire traction trying to bend the axle over that 13" length between the UCA and LCA pickups. Geometrically, it looks like it can be made to work OK. But it also has to work from the structural strength and deflection points of view.

Axles can be reinforced, and I think at some level the drag racers have to do something along the lines of axle assembly reinforcement. For a street car however, it seems an awful lot like putting a heavy band-aid on a situation that could/should be avoided in the first place.


Norm

[jamesinark]

what norm seems to be saying can be seen in other forms of motorsports such as rock crawling and off road racing.Their lower control arms are mounted at or near the axle ends and angle in from there.He is right on with the band-aid metaphor as seems to be born out from looking at any type of suspension setup to take high horizontal and lateral loads at the same time.I understand you're trying to do something innovative as I seem to be going about my build with a lot different modifications that some people may think unnecessary.But you have to keep in mind safety and durability at all times.

[exwestracer]

Keep in mind that in ANY type of 4 link system, ONLY the lower links are actually pushing the car forward under acceleration. The upper links are in tension trying to resist the pinion climb. On a high HP, big tire car, it's a much better idea to have the lower links pointed straight ahead and pushing directly into the frame rails, rather than a crossmember.

The same applies to a 3 link or torque arm suspension, BTW.

[thinkfastroth]

Ok hopefuley I understand this correctly. If I mount the lower as in a true satchel and shorten the uppers this should getrid of the large cornering forces and help with traction issue.
Thanks all for the help and happy thanksgiving.
Jerred

[thinkfastroth]

Norm I have some new numbers.
upper links x y z
frame 18 16 16
axle 0 16 16.5
lowerlinks
frame 24 3 8
axle 0 16 6.25

I would like to get youur thoughts, if it dosn't look like a good safe idea maby it's time to look at a 3 link.

thanks for your help Jerred

[Norm Peterson]

51623

The lower link loads are still going to be larger than the contact patch forces, but the axle tubes are a lot better off. I'm avoiding putting any specific numbers on the link loads, but working from the total loading on the axle you should include generous factors of safety (I've heard reliably that 5 for vertical, 4 for fore/aft, and 3 for lateral are reasonable factors for a road car). Those factors do not consider that either fore/aft or lateral loads applied to a skewed link will result in the link loads being larger than the applied loads.


Norm

[jamesinark]

Keep in mind that in ANY type of 4 link system, ONLY the lower links are actually pushing the car forward under acceleration. The upper links are in tension trying to resist the pinion climb. On a high HP, big tire car, it's a much better idea to have the lower links pointed straight ahead and pushing directly into the frame rails, rather than a crossmember.

The same applies to a 3 link or torque arm suspension, BTW.

I have seen the afore mentioned setup on a few rock crawlers and I have the impression that the angle is not drastic.Usually just enough to improve on approach angle and clearance.They don't actually meet in the center just a little inside of the frame rails usually and they tend to use a wishbone upper link fairly often,but I am not certainly an expert on this discipline as I have only done a couple of 4 link conversions on my last S10 4x4 four a hunting rig.I tend to get way offroad and trail sometimes when I used to use dogs for sport(no killing).I will defer to your experience as I am in awe of your knowledge and willingness to share it.

[Norm Peterson]

About the only geometric requirement that exists for any version of the triangulated (or converging) 4-link suspension is that at least one of the links must not be parallel to the vehicle centerline.

In practice, it's nice to have symmetry and enough angularity in either the upper or the lower pair to bring the link forces down to reasonable levels and not let the axle move too far laterally by virtue of (curse of?) bushing compliances and bracket deflection.


Side note - only yesterday I happened to see a bagged S10 with a rear suspension an upper wishbone. Two pivots on the axle side and a single frame attachment.


Norm

[exwestracer]

The "true" Satchell design, as I have come to understand it, has the straight links on top and the angled links or wishbone on the bottom. This is done to lower the roll center.