AMT Sock-it-to-Me Corvette MSP: Gasser Suspension Dynamics 101, Jan. 29

[Ace-Garageguy]

1 hour ago, OneTrickPony said:

...The rules issues you have pointed out don't bother me at all...

I agree with you on all points, but I wanted to make the model NHRA class-legal for the period, just so it could be a viable "what if" from anywhere in the country.

[Ace-Garageguy]

14 minutes ago, R. Thorne said:

In order for this to be more “period correct”, it should have a blown small block chevy ( like Jim Sermersheim’s corvette which I saw run back in the sixties).  I doubt that anyone ran a blown 409.  You do good work, sir, and your contributions to this forum is immense.  

Thanks for your interest and comments. Like most of my builds, this one isn't intended to represent anything that actually ran, but something that could have run under NHRA class rules anywhere they were strictly enforced.     

There's nothing in the rules to prohibit a blown 409, and there were a few folks who ran 'em in other classes...   

[Ace-Garageguy]

I glassed the two sections of the hood panel together, as it's going to be the plug for a near-scale-thickness panel, and needs to be stout at the join. I also straightened out the edges of the old hood and opening with strip stock filed flat.

This is my ace number one assistant, chief parts chaser, and occasional foot warmer. He doesn't seem to notice (or care if he does) he's now way too big for the box.

Progress on curing the flat-face appearance the AMT 4-eyed Corvettes of this generation seem to me to have. The grille openings have been extended with .010" styrene strip, as shown earlier, and will be filled.

We're getting there. The door lines are also being filled, as this is supposed to be a lightweight one-piece body (pre-funnycar, but moving towards that idea).

 

 

 

 

[iBorg]

I wish all the photos were still here. Looks like a very interesting build.

[Ace-Garageguy]

21 minutes ago, iBorg said:

I wish all the photos were still here....

From my end, they appear to be. All the shots I posted on this one are on the MCM server.

[iBorg]

I don't have them from page 1 and 2. Those on page 4 are very educational.

[Ace-Garageguy]

19 minutes ago, iBorg said:

I don't have them from page 1 and 2. Those on page 4 are very educational.

I have no idea what's going on. I did a reverse image search on several of those pix, and Google is seeing them and tracks them back to the correct MCM thread.

Anybody else not seeing photos on pages 1 & 2?

[Bernard Kron]

I'm posting this comment so that it flags any activity. I had forgotten about this one. I've got a Deuce started with the idea of giving it a lightweight tubular frame. The chassis work on this, sans the high front axle, is just what I need for inspiration - simple, clean and structurally apt.

Edited December 4, 2018 by Bernard Kron

[tim boyd]

10 hours ago, Ace-Garageguy said:

I have no idea what's going on. I did a reverse image search on several of those pix, and Google is seeing them and tracks them back to the correct MCM thread.

Anybody else not seeing photos on pages 1 & 2?

Bill, photos on page 1 and 2 come through fine here. 

Really interesting and relevant topic and build process. 

Glad it got brought back to the front of the forum folder as somehow I missed it when you got started on the project a couple of years back.  

Thanks for taking us along for the ride....and look forward to seeing progress as it occurs in the future….TIM

 

Edited December 4, 2018 by tim boyd

[Jonathan]

Wow, thank you for sharing so far.  This is very inspiring and beautiful work!

[iBorg]

Now the photos show.....they're worth the wait.

[Ace-Garageguy]

On 12/4/2018 at 1:13 AM, Bernard Kron said:

I'm posting this comment so that it flags any activity. I had forgotten about this one. I've got a Deuce started with the idea of giving it a lightweight tubular frame. The chassis work on this, sans the high front axle, is just what I need for inspiration - simple, clean and structurally apt.

Glad to be of some help, Bernard. Thanks for the comment.

18 hours ago, iBorg said:

Now the photos show.....they're worth the wait.

Thank you sir. Glad you think so.

18 hours ago, Jonathan said:

Wow, thank you for sharing so far.  This is very inspiring and beautiful work!

And thank you. sir.

[Ace-Garageguy]

On 12/4/2018 at 9:14 AM, tim boyd said:

...Really interesting and relevant topic and build process...  

Thanks for taking us along for the ride....and look forward to seeing progress as it occurs in the future….TIM

Thanks Tim. As with most of what I build, this one became lots more involved than I'd originally intended, but sitting back and taking stock of what it needs to get to completion, it's not all that much. Just the somewhat repetitive "work" parts of any build I have to discipline myself to get through. 

[cobraman]

Great project Bill. Glad to see you plugging along on it. Cool helper you have there. May have to get another for myself at some point.

[Ralph Henderson]

Amazing work Bill.  I am especially interested in your fiberglass techniques for scale thickness fidelity.  I fear as I get closer to finishing my "BattleBird", I'm going to run into those challenges with the tonneau cover.  At some point in the future I may have some questions?? 

Anyway, GREAT build and attention to detail.

Edited December 6, 2018 by Ralph Henderson

[bisc63]

My thanks as well! Lots of cool tips to digest here, especially regarding the mock-up stage,setting stance, etc. Very thoughtful of you to share; I know it takes time!

[Ace-Garageguy]

On 12/5/2018 at 6:56 PM, Ralph Henderson said:

... I am especially interested in your fiberglass techniques for scale thickness fidelity.  I fear as I get closer to finishing my "BattleBird", I'm going to run into those challenges with the tonneau cover.  At some point in the future I may have some questions?? 

Thanks for your interest and comments. I've been following your BattleBird project. Love it, and the real car it's based on. Your pix of the uber-rare Y-block injection are most appreciated as well.

Far as the tonneau goes, here's another way to do one...and feel free to ask away.  

 

On 12/5/2018 at 11:32 PM, bisc63 said:

My thanks as well! Lots of cool tips to digest here, especially regarding the mock-up stage,setting stance, etc. Very thoughtful of you to share; I know it takes time!

Glad you found something worthwhile here, and thanks.  

On 12/5/2018 at 10:39 AM, cobraman said:

...Glad to see you plugging along on it. Cool helper you have there. May have to get another for myself at some point.

Just trying to maybe finish something in this lifetime. And the furry helper found me. Just couldn't ignore the sound of a kitten crying outside in the middle of the night. I like almost all animals, but I have a special fondness for cats. Probably because they share something like 96% of their DNA with lions and tigers. Little scale model predator beasts. Very low maintenance too. I like low maintenance. 

[Ralph Henderson]

4 hours ago, Ace-Garageguy said:

Thanks for your interest and comments. I've been following your BattleBird project. Love it, and the real car it's based on. Your pix of the uber-rare Y-block injection are most appreciated as well.

Far as the tonneau goes, here's another way to do one...and feel free to ask away.  

 

Thanks Bill.  I'm not sure which way I'm going with the tonneau and fairing yet on this build, but I do want to learn more about your

'glassing technique...

Edited December 9, 2018 by Ralph Henderson

[Ace-Garageguy]

So...we gotta have some kind of "traction bars". Traction bars simply keep the rear end from rotating relative to the car during brutal acceleration. When the rear end "winds up", the tires usually dance around on the pavement, losing traction. Nasty launch characteristics and broken parts result if the rotation of the axle isn't controlled.

I could use the old-school style that goes by that name, but they're a little lame for a serious, blown car.

Ladder or lift bars will give more precise control, but they don't work well with parallel semi-elliptical springs unless you jump through some hoops.

Because of the (usually) different distance between the axle and the forward end of the spring eye, relative to the distance from the axle to the forward ladder-bar pivot, binding in the suspension is inevitable, again with jumping, shuddering launch characteristics, and more broken parts.

This can be alleviated by allowing the axle to slide and rotate somewhat relative to the springs, but keeping it closely controlled relative to the chassis by the ladder bars. Several ways are available to do this, and the parts are relatively small and difficult to fabricate cleanly in 1/25 scale. I've chosen a simple method to represent, but it won't be 100% accurate...it will simply give the impression of being there, just to keep the build honest, with thought given to function.

The ladder bars I have to pick from are shown below. Because of constraints caused by the floor and the frame rails on this car, none of them really work acceptably well. But not to worry. The black ones, salvaged from a Revell SWC Willys gasser, can be modified.

But first, I had to get the curve of the springs correct to maintain the previously established ride-height, taking into consideration the effect the axle "sliders" will have on height. Then I laminated additional leaves from strip stock. The ends of the single-leaves are only .020" styrene, and won't support the full weight of the model...but the shocks, when installed, will. I'd kinda wanted to have everything working back here, but if I do, I'll have to fab brass springs, shocks with sliding sections, and the thing will just go into limbo in the meantime...with all my other builds. So we're gonna fake it.

This last shot shows how the modified Willys kit parts will fit. The axle end will be gusseted heavily, with an additional upper diagonal tube, and the forward end will be fitted with a pivoting eye that catches the frame just at the engine plate. Classic lift-bar design, and it will all clear the floors.

 

 

[Deuces]

On 12/3/2018 at 8:51 PM, Ace-Garageguy said:

I glassed the two sections of the hood panel together, as it's going to be the plug for a near-scale-thickness panel, and needs to be stout at the join. I also straightened out the edges of the old hood and opening with strip stock filed flat.

This is my ace number one assistant, chief parts chaser, and occasional foot warmer. He doesn't seem to notice (or care if he does) he's now way too big for the box.

Progress on curing the flat-face appearance the AMT 4-eyed Corvettes of this generation seem to me to have. The grille openings have been extended with .010" styrene strip, as shown earlier, and will be filled.

We're getting there. The door lines are also being filled, as this is supposed to be a lightweight one-piece body (pre-funnycar, but moving towards that idea).

 

 

 

 

Looks just like my little buddy..... ?

[Ace-Garageguy]

PLEASE:   TO EVERYONE ALL OVER THE FORUM >>>> IF YOU"RE GOING TO QUOTE SOMETHING, HOW ABOUT DON'T QUOTE THE ENTIRE POST WITH ALL THE PICTURES? IT'S EASY TO EDIT A QUOTE DOWN TO JUST ONE PHOTO, OR BETTER YET, JUST THE TEXT YOU"RE COMMENTING ON.

ALSO:   PLEASE BE POLITE AND DON'T POST YOUR OWN PHOTOS ON SOMEBODY'S BUILD THREAD, UNLESS IT'S TO ILLUSTRATE A TECHNICAL POINT OR FOR REFERENCE PURPOSES. IT GETS CONFUSING SOMETIMES AS FAR AS WHOSE WORK IS WHOSE, ETC.

THESE POINTS HAVE BEEN BROUGHT UP MULTIPLE TIMES IN "GENERAL" AND OTHER AREAS, BUT SOME NEWER FOLKS HAVEN'T HEARD. 

NOT BEING MEAN...JUST TRYING TO CONSERVE SERVER SPACE, AND MAKE IT EASIER TO READ THROUGH THREADS WITHOUT SEEING THE SAME IMAGES COPIED NEEDLESSLY.

THANK YOU.

______________________________________________________________________________________________________________________

I'm pretty particular about how wheels relate to fenders, and I make an effort to keep things right. I've seen a lot of otherwise very nice models spoiled when the wheels / tires are way off center in their openings.

I glued the front axle in to a fixture on the frame (made earlier) that holds it in the correct position relative to the body, established during the mockup phase. I used white glue that's strong enough to hold the axle while I work on it, but easily removable when I'm done. You probably can't see it here, but the axle has the correct camber made into it, and the caster has been set by leaning the kingpin bosses back at the top. When the wheels are posed, the steering will move correctly and look like a real car. The springs shown here are single strips of .020" styrene with rod to simulate spring eyes on the ends.

This little part I made is one of a pair of spring brackets that would be welded to the axle. U-bolts would go over the axle, through holes in the brackets, and get nuts that clamp the axle to the spring and keep it from rotating.

Here's the first one in place, very carefully located on the axle.

With both brackets "welded" in place, I was able to laminate a few more spring leaves in place with the right curvature, made from .015" styrene strip. I laminated more leaves on the rears too.

Here the finished springs are in place on the axle, pinned from below so they'll go back in exactly the right location after painting and "plating" the axle.

I buggered one end of the rear axle while working it down to fit the "sliders", so I took both ends off and replaced them with tubing. The mods to the lift bars are also proceeding in this shot.

Width check after trimming the ends to length. I ended up needing to use a .030" spacer on each side to get the tires exactly where I wanted them.

After the axle was primered to check some other repairs (it was salvaged from a gluebomb SWC Willys), I measured and cut a section out of the driveshaft to fit the previously mocked-up axle location, and to help me check the pinion angle relative to the trans. Yeah, it's not going to run, but I'm just wired to do things as if it was.

Finally, with all that fahoolin' aboot out of the way, I'm able to glue the lift bars to the axle housing, using the fixtures I made to hold the axle in the right place, and one more to hold the ends of the bars in position. Much like building a real car. There's enough clearance for the tail to squat about 4 scale inches when the car accelerates, without having the lift-bars hit the floor. Should be plenty.  

Up on her feet again, to verify I got everything in the right place BEFORE the glue gets entirely hard, and to give myself a little more motivation to keep going.

 

 

[Snake45]

44 minutes ago, Ace-Garageguy said:

 

I'm pretty particular about how wheels relate to fenders, and I make an effort to keep things right. I've seen a lot of otherwise very nice models spoiled when the wheels / tires are way off center in their openings.

Then photos of the real first-generation Chevy II AWB funny cars must drive you crazy!  

Moving on, I like what you're doing with the front axle here. Mounting the axle underneath the springs is almost guaranteed to give a too-nosehigh stance, and yet that's how most kit manufacturers, model builders, and even too many current real-car builders do it. I have a feeling I'm going to be doing some scratchbuilding very similar to your work here in the near future. DO drive on and get this one done! 

[afx]

Coming along nicely.

[Ace-Garageguy]

3 hours ago, afx said:

Coming along nicely.

Thanks.

15 hours ago, Snake45 said:

 

...Moving on, I like what you're doing with the front axle here. Mounting the axle underneath the springs is almost guaranteed to give a too-nose-high stance, and yet that's how most kit manufacturers, model builders, and even too many current real-car builders do it...

Yeah, and in an effort to get the nose down to a reasonable height, a lot of "straight axle" gassers actually use dropped axles. Kinda silly in my opinion to jack the car way up with leaf-springs on top of the axle, and then have to drop it back down somewhat with a dropped-axle.

It makes far more sense to use a real straight axle, easily fabricated from tube (on a real car OR a model), and choose (or make) springs to put the thing at the right ride height.

Another thing...using a dropped axle on a real car is a handling compromise at best. It's almost mandatory for a hot-rod, to get one low, but the dropped ends act like levers, multiplying the brake torque trying to twist the axle and wrap the springs up. Old-school gassers and similar classes like this are pretty squirrelly to start with, due to the very high center of gravity. No logic in introducing more variables and unhappy forces acting to destabilize a car any more than absolutely necessary.

Of course, if you're building a car from junkyard parts, you use what you can find, but as it's relatively easy to fabricate a straight axle, and have leaf springs made (or re-curved) to get exactly what you want, it makes more sense to me to go that route.

[Ace-Garageguy]

Though this model is NOT a gasser, it's close in general concept, and the overall design goals of the builders of a car like this would be very similar to guys building gassers back in the dim recesses of time. Getting maximum "weight-transfer" towards the rear under acceleration is Job 1, especially necessary where the width and rubber compounds of the slicks available then made them considerably less-sticky than what we're used to today.

Contrary to widely popular opinion these days, the normal at-rest stance of a period gasser WAS NOT the nose-to-the-sky attitude in evidence in so many "nostalgia" cars, both real and model.

Despite a FEW period photos to the contrary, the VAST MAJORITY of real in-period gassers sat LEVEL at rest, and only developed the extreme nose-high attitude during launch. Again, this is not my "opinion". It is a simple FACT that can be verified by anyone researching period class rules, and photographs of cars FROM THE ERA.

One of the reasons the Stone-Woods-Cook Willys gasser became so famous is because of it's great and consistent ability to "hook up". The guys who put the car together were wizards who hit on a magic combination, and I've been studying it to use on this build.

My interest in the SWC chassis setup began many years ago, but it's surfaced again because the leaf springs I fabbed for this build won't support the car's weight. I'm going to have to take that load with the shocks, and started scrounging through kits to see what I could find that's appropriate. I happened to look in the vintage Revell SWC Willys kit, and wouldn't choo know, I remembered a few things.

Though there's never really been any in-depth engineering analysis of the SWC car's setup published (as far as I know), Revell got things pretty righteous back in those days, and the shocks in the kit add to an interesting story. 

The rear end of the SWC Willys gasser was set up pretty "loose", on quarter-elliptic springs that allowed the body to move quite freely up and down relative to the axle. Side-to-side motion was controlled by a simple Panhard bar, and axle torque-reaction during acceleration was controlled by long traction bars that also worked as "lift bars", very effectively raising the front of the car as the rear tended to squat on the softish springs. Smallish shocks at the rear prevented that end of the body from rising again quickly, while much larger shocks at the front tended to hold the nose high after those springs unloaded at launch. NOTE: The American term "shock absorbers" leads to much misunderstanding of what these parts actually do. The British term "dampers" is accurate, as they "damp" out excessive "boingity-boingity-boingity" as the springs try to oscillate after they're displaced. They do NOT absorb shock, nor do they add to the car's static spring-rate (unless they're specifically designed to do so, gas-filled or coil-over units).

Old drag racing guys will remember that, before you could just buy everything out of catalogs (like 90/10 shocks), we'd routinely use worn-out shocks that were much stiffer in one direction than the other to get exactly this kind of car control (or hack them open, change the valving, and fill 'em with STP...) and this general combination of damping front-to-rear is largely responsible for the characteristic appearance of gassers maintaining the nose-high attitude well down the 1/4 mile, though they'd usually settle to level at the end.

Anyhaps...I found some loose but clean Revell SWC Willys gasser parts hiding out in a mess of other miscellaneous bits I've never sorted, and as the rear end and lift bars in this thing are already based on Revell SWC Willys gluebomb parts, I'll be using the fronts, suitably modified to fit this build, and rears of a size similar to what was under that end of that car as well.

Happy trails. 

PS. There will be a test on this material at the end of the semester.