The Project Anklebiter Build Thread., 8/29 Lid latches and glamor shots... Options

[plymouth37]

The trailing arm will push up on what is now the open bolt hole in the pivot arm. That upward motion will cause the trailing arm to rotate in a counter-clockwise direction (on the passenger side). The upward force of the trailing arm is counteracted by the vertical and horizontal forces of the shock, given the angle of the shock about 392 pounds of its force will be acting horizontally on a point that is 5" above the pivot point while around 75 pounds of the shock resistance acts vertically on a point 7.5" off of the pivot point. These leverage points are counteracted by the trailing arm that attaches at a point 10" off of the pivot point. Since the trailing arm has a mechanical advantage on the shock the 400lb/in in the shock gets reduced down to about 250lb/in at the trailing arm which is just about what I want. Not sure if that clears anything up, I won't know for sure exactly how this thing will react until I get everything done and jump around on it (IMG:style_emoticons/default/wink.gif)

[MDG]

The trailing arm will push up on what is now the open bolt hole in the pivot arm. That upward motion will cause the trailing arm to rotate in a counter-clockwise direction (on the passenger side). The upward force of the trailing arm is counteracted by the vertical and horizontal forces of the shock, given the angle of the shock about 392 pounds of its force will be acting horizontally on a point that is 5" above the pivot point while around 75 pounds of the shock resistance acts vertically on a point 7.5" off of the pivot point. These leverage points are counteracted by the trailing arm that attaches at a point 10" off of the pivot point. Since the trailing arm has a mechanical advantage on the shock the 400lb/in in the shock gets reduced down to about 250lb/in at the trailing arm which is just about what I want. Not sure if that clears anything up, I won't know for sure exactly how this thing will react until I get everything done and jump around on it (IMG:style_emoticons/default/wink.gif)

Halfway through reading that I had to take a nap. I said it before, pages back - mad scientist at work here.

God I love this thread.

[plymouth37]

The trailing arm will push up on what is now the open bolt hole in the pivot arm. That upward motion will cause the trailing arm to rotate in a counter-clockwise direction (on the passenger side). The upward force of the trailing arm is counteracted by the vertical and horizontal forces of the shock, given the angle of the shock about 392 pounds of its force will be acting horizontally on a point that is 5" above the pivot point while around 75 pounds of the shock resistance acts vertically on a point 7.5" off of the pivot point. These leverage points are counteracted by the trailing arm that attaches at a point 10" off of the pivot point. Since the trailing arm has a mechanical advantage on the shock the 400lb/in in the shock gets reduced down to about 250lb/in at the trailing arm which is just about what I want. Not sure if that clears anything up, I won't know for sure exactly how this thing will react until I get everything done and jump around on it (IMG:style_emoticons/default/wink.gif)

Halfway through reading that I had to take a nap. I said it before, pages back - mad scientist at work here.

God I love this thread.

That was quite possibly one of the most boring things I have ever written. (IMG:style_emoticons/default/biggrin.gif)
The shape of the pivot arm is deceiving, the shock is given a lot more leverage than it looks like it should have.
And since the trailing arm has a mechanical advantage on the shock the spring needs to move less to counteract it. The spring will only have a 2-3 inch range of compression.
While I am on here: Have a Happy Thanksgiving Everybody! (IMG:style_emoticons/default/beerchug.gif)

[MDG]

Halfway through reading that I had to take a nap. I said it before, pages back - mad scientist at work here.

God I love this thread.

That was quite possibly one of the most boring things I have ever written. (IMG:style_emoticons/default/biggrin.gif)
The shape of the pivot arm is deceiving, the shock is given a lot more leverage than it looks like it should have.
And since the trailing arm has a mechanical advantage on the shock the spring needs to move less to counteract it. The spring will only have a 2-3 inch range of compression.
While I am on here: Have a Happy Thanksgiving Everybody! (IMG:style_emoticons/default/beerchug.gif)

To be clear, Dana, my sudden case of narcolepsy had nothing to do with boredom. In fact, I found your explanation to be enlightening. The nap was to give my brain a rest before continuing.

[scotty b]

The trailing arm will push up on what is now the open bolt hole in the pivot arm. That upward motion will cause the trailing arm to rotate in a counter-clockwise direction (on the passenger side). The upward force of the trailing arm is counteracted by the vertical and horizontal forces of the shock, given the angle of the shock about 392 pounds of its force will be acting horizontally on a point that is 5" above the pivot point while around 75 pounds of the shock resistance acts vertically on a point 7.5" off of the pivot point. These leverage points are counteracted by the trailing arm that attaches at a point 10" off of the pivot point. Since the trailing arm has a mechanical advantage on the shock the 400lb/in in the shock gets reduced down to about 250lb/in at the trailing arm which is just about what I want. Not sure if that clears anything up, I won't know for sure exactly how this thing will react until I get everything done and jump around on it (IMG:style_emoticons/default/wink.gif)

Halfway through reading that I had to take a nap. I said it before, pages back - mad scientist at work here.

God I love this thread.

A NAP ?? REALLY ? Half way through it I had to (IMG:style_emoticons/default/jerkit.gif)

[PeeGreen 914]

The trailing arm will push up on what is now the open bolt hole in the pivot arm. That upward motion will cause the trailing arm to rotate in a counter-clockwise direction (on the passenger side). The upward force of the trailing arm is counteracted by the vertical and horizontal forces of the shock, given the angle of the shock about 392 pounds of its force will be acting horizontally on a point that is 5" above the pivot point while around 75 pounds of the shock resistance acts vertically on a point 7.5" off of the pivot point. These leverage points are counteracted by the trailing arm that attaches at a point 10" off of the pivot point. Since the trailing arm has a mechanical advantage on the shock the 400lb/in in the shock gets reduced down to about 250lb/in at the trailing arm which is just about what I want. Not sure if that clears anything up, I won't know for sure exactly how this thing will react until I get everything done and jump around on it (IMG:style_emoticons/default/wink.gif)

Halfway through reading that I had to take a nap. I said it before, pages back - mad scientist at work here.

God I love this thread.

A NAP ?? REALLY ? Half way through it I had to (IMG:style_emoticons/default/jerkit.gif)

(IMG:style_emoticons/default/laugh.gif)

[McMark]

Will the trailing arm connect to the lever arm via a rod? Or will it be a direct connection. Your explanation makes sense. It seems like a small range of motion, but you sound like you've done your math and I'm just armchair speculating. It's cool looking, regardless. (IMG:style_emoticons/default/drooley.gif)

[rick 918-S]

Be careful you don't build in a metronome effect with the vertical connecting rod from the trailing arm to the rocker. Could cause a weird vibration at speed. Just an arm chair observation. (IMG:style_emoticons/default/biggrin.gif)

[jd74914]

Cool. I like that shock placement.

One more observation: your new rocker is the perfect place to add attachment for a sway bar arm for fine tuning. Just think if it; you could have a blade arm with cabin stiffness adjusters... (IMG:style_emoticons/default/laugh.gif)

[roadster fan]

Hey Dana thanks for posting all the progress on your project. I love learning along the way and am fascinated by suspension design. I drew up your arm and shock into a simple CAD program as I was skeptical that you could compress that that shock 2.5"-3" with the geometry you designed in.

I discovered (and i will attempt to upload a pic of my drawing but have to convert it i think) that you can compress your shock and spring 2.5" with a vertical trailing arm motion of 4.25" which I believe is possible in a 914. But I noticed that the actuator rod between the trailing arm and the cantilever arm has to be 6.25" long. This is due to the cantiliver arm moving on an arc away from the trailing arm so the mounting hole on the cantilever arm gets further away as it moves vertically.

It is probably hard to visualize without my drawing but I think your design would work fine as long as the actuator rod is at least 6.25" long which means it probably would have to mount an 1" to 1.5" below the shock bolt hole on the trailing arm. Your drawing shows the actuator rod to be 5" long I think but that would try to pull the trailing arm inboard causing a binding issue. This is all a novices observations, I could be completely off my @$$ and confused, that has happened before (IMG:style_emoticons/default/dry.gif)

I love your project and cant wait for more pics of the progress,

Jim

[geniusanthony]

39k views. keep it up Dana, great work.

[plymouth37]

Hey Dana thanks for posting all the progress on your project. I love learning along the way and am fascinated by suspension design. I drew up your arm and shock into a simple CAD program as I was skeptical that you could compress that that shock 2.5"-3" with the geometry you designed in.

I discovered (and i will attempt to upload a pic of my drawing but have to convert it i think) that you can compress your shock and spring 2.5" with a vertical trailing arm motion of 4.25" which I believe is possible in a 914. But I noticed that the actuator rod between the trailing arm and the cantilever arm has to be 6.25" long. This is due to the cantiliver arm moving on an arc away from the trailing arm so the mounting hole on the cantilever arm gets further away as it moves vertically.

It is probably hard to visualize without my drawing but I think your design would work fine as long as the actuator rod is at least 6.25" long which means it probably would have to mount an 1" to 1.5" below the shock bolt hole on the trailing arm. Your drawing shows the actuator rod to be 5" long I think but that would try to pull the trailing arm inboard causing a binding issue. This is all a novices observations, I could be completely off my @$$ and confused, that has happened before (IMG:style_emoticons/default/dry.gif)

I love your project and cant wait for more pics of the progress,

Jim

Thanks for drawing that up, I look forward to seeing it! Totally agree about a potential binding issue with the connecting rod, I went old skool and replicated each component from my diagram on trace paper last week and simulated its movement, the 5" rod does tweek out a good amount as the suspension reaches its outer limits of rotation. I was going to tack in the suspension mounts and then really dial in the position and length of the rod, thanks for the tip about the length, longer is definitely better, luckily the shocks and the connecting rod will be adjustable so I should be able to fine tune within reason once everything is in position and making a mount that adds a couple inches to the connecting rod should be pretty doable. Luckily since the motion of the connecting rod is fairly vertical I can make the connecting rod any length I need to without effecting the suspension geometry too much.

[plymouth37]

Will the trailing arm connect to the lever arm via a rod? Or will it be a direct connection. Your explanation makes sense. It seems like a small range of motion, but you sound like you've done your math and I'm just armchair speculating. It's cool looking, regardless. (IMG:style_emoticons/default/drooley.gif)

It will be a heim joint connection to compensate for the various crazy directions the different parts of the suspension will be going.

[roadster fan]

Well I slept on this, and like I suspected I was wrong (IMG:style_emoticons/default/headbang.gif)

Attached below is a bitmap of the drawing as corrected this morning. Looks like a 5" actuator arm will work fine, and you would get the 2.5" compression with a vertical trailing arm movement of 4.22". Like I said I like learning along the way, and as I should have suspected YOU had it worked out right from the beginning (IMG:style_emoticons/default/chair.gif)

Here is the drawing:

[plymouth37]

Nice rendering! It is so much easier to understand this drawing than anything I have created, thanks for the help!
I may still need to make the connecting rod a little longer, as the suspension unloads the pivot arm kicks out over the trailing arm and there is a potential binding/contact issue between the trailing arm and the connecting rod there, still won't know for sure until I can tack in the mounts and run the suspension through its entire range of motion though.

[wingnut86]

......Got Milk?

(IMG:style_emoticons/default/chowtime.gif) (IMG:style_emoticons/default/chowtime.gif) (IMG:style_emoticons/default/chowtime.gif)

[db9146]

Okay, I'm going to go ahead and stick my neck out.....

The trailing arms pivot from the front of the arms so any compression will tend to ultimately move the rear wheel forward given enough travel, correct? However, it looks like the planned mounting point for the horizontal shocks is going to be behind the wheel centerline. This makes it seems to me that there will be a twisting motion on the linkage and shocks.

Takes a lot more time to "conduct class" while doing the work rather than just forgetting about "schooling" all of us and completing the project, huh?

[stownsen914]

Really cool stuff. I actually am in the middle of redoing the suspension on my 914 track car, and am currently modeling my ideas using susprog, a suspension analyzer. It's extremely helpful to test out stuff that i otherwise would probably discover only after building the parts (IMG:style_emoticons/default/smile.gif) I haven't read your whole thread, but it might be worth trying something like that if you haven't already done so. Susprog also has an option to visualize your design while moving the suspension through it's full range of motion.

Edit -- modified post after I realized that your design already has a push rod. That part should be OK. Only other thing a lot of bending forces on the rocker. I would think the push rod would try to push the rocker forward and rearward (relative to front/rear of the car). Would a wider base help where it mounts to the chassis?

Scott

[plymouth37]

There is a potential for bending in the arms but I would think that since the entire cantilever component moves on a single plane and is connected to the trailing arm with a heim joint the chances of significant off axis movement occurring would be minimal. To counteract any twisty forces that do appear I had planned on making wide reinforced attachment points on the chassis and the arms have already been built with additional reinforcement points at that point.

[plymouth37]

I decided to take a break from the suspension to wrap up a couple little projects on the car.
A year or so ago I pieced up this intercooler system but since I was in an apartment couldn't weld it up.

Now that I have my house I can play with welders all I want so I decided to weld up the intake system, I also welded in a bung for the boost gauge sender and a ground stud for the sender.