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Old 03-15-2016, 06:25 PM   #151 (permalink)
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Awesome work! What clutch is that you are using?
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Old 03-16-2016, 02:31 PM   #152 (permalink)
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Back to the exhaust manifolds, why don't you just make your own headers. From what I've seen on don't think it would be a problem.
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Old 03-16-2016, 04:17 PM   #153 (permalink)
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Quote:
Originally Posted by TGomes1987 View Post
This Quadratec article has some pretty good information on shackle angle and how it affects spring rate.

Jeep Parts, Jeep Accessories & Jeep Soft Tops From The Jeep Parts Experts - Quadratec

Picture from the article, I've seen this picture other places as well. Quick reference for shackle angle.



I also seem to recall reading somewhere that when fully drooped out you want your shackle angle to be pointing roughly in line with your leaf spring, hopefully someone can comment on that with more info.

EDIT: I just saw you already discussed shackle angles a few pages ago looks like you set it up just like the article suggests!
Thanks for the link, I'm glad you shared it for everyone. I had read that article when I was sorting out my spring geometry, and it is really a good one. I should have mentioned it. I found it to be really helpful, and I tried to target the geometry on my hangers to achieve a neutral shackle effect on the spring rate - i.e. to achieve the "right angle at rest" geometry. In my case, that was little tricky as I set the hanger position before the rails were actually together - I set the position of the hanger threaded inserts before I welded the rails together so I could weld the fixed hanger threaded bosses before capping the rails and doing the stack welds. To try to head off problems with that approach, before I built the new frame, I had mocked up the geometry under my old frame rails with the old axles, based on the factory YJ frame drawing, YJ hanger and shackle specs, and then cycled the springs with one leaf. I ended up shortening the eye to eye fixed to shackle hanger distance from that starting point very slightly to reduce inversion risk. It was initially very close to inversion- the shackle was in line with the spring at full droop, and I could kick it over with a hammer tap. I set the distance between the eyes of the hangers just a little closer together than the factory dimensions to get a little farther away from inversion - i.e. leave a little more tilt at full droop. Doing the initial estimation from drawings , parts measurements, and making adjustments for differences in my stack rail elevation height and different than stock springs could lead to some errors in estimation, and so i'm glad I mocked it all up before setting the position on my new rails! I also have some ability to do some final tweaking by making revised fixed hangers to adjust the eye position forward or backward if needed. More comments in reply to next messages...

Last edited by CJ3BL; 03-16-2016 at 04:20 PM.
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Old 03-16-2016, 04:29 PM   #154 (permalink)
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I would vote no on this. The chance of shackle inversion, especially in front if your not shackle reversed, goes WAY up. I would try and maintain some angle on the shackle at full droop. I don't think it takes much, but i wouldn't want to see the shackle being 'pulled' in tension at full droop.
I agree with Meiser- I don't think it's desirable to have the shackle in line with the spring at droop- too much risk of inversion. At the same time, TCGomes brings up the very valid point that inversion avoidance could be addressed with an anti-inversion stop or boomerang shackles set up for anti-inversion use. In my case, what I was trying to shoot for is to hit a neutral rate /90 degree at rest target, and avoid inversion by having a little shackle angle versus the arc of the spring at full droop, so that I wouldn't need to clutter things with an anti-inversion stop of some sort. It will take some more weight and setting up the full spring pack to see how close I got!
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Old 03-16-2016, 05:42 PM   #155 (permalink)
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I would avoid the spring being inline with the shackle.

Beyond that, the droop angle is likely going to be driven by the resting shackle angle. I am also not a fan of removing spring clamps nor of pulling the spring past its free arch on droop (shackle in tension). Ideally we shouldn't be pushing the spring too far into negative arch to much or too often. That seems to be fairly hard on springs over time.
Agreed, I've been thinking of it like this: Target the hanger and shackle geometry to achieve the resting angle you want first (for the effective spring rate effect you're after), then check to make sure you don't have an inversion problem. If too much risk of inversion, then compromise the resting angle a little, or lengthen then shackle, or lastly resort to stops. In my case, I want to target a neutral effect on spring rate (90 deg angle at rest), and try to avoid needing stops to prevent inversion. With the 2.5" lift RE springs I'm using, 4.25" long shackles, and the hanger geometry I set-up, I think it may work out as I hope. The earlier photos I posted show that the shackles have a little angle at full droop so I think I'm OK on that end of the travel- although it's close! I have to guess at this point as to final rest position with the full spring pack and full weight of the rig once completed. Looking at the range of the shackle position between current rest position (with just the frame weight) to full compression (by clamping the spring to compress it) it looks like the final resting position may be close to where I want. The other aspect of this is whether the whole thing will sit level with this spring choice...Likely some fine tuning ahead, but I think that so far it's looking OK. Crossing my fingers!
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Old 03-16-2016, 05:51 PM   #156 (permalink)
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Awesome work! What clutch is that you are using?
Fancy you should ask, Centerforce! I'm using a Centerforce CF700160 Flywheel, CTFC165552 Pressure Plate, CTFC281226 Clutch Disc, and N-1439 Bearing. Mix and match of GM, Ford and Jeep applications.
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Old 03-16-2016, 05:55 PM   #157 (permalink)
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Back to the exhaust manifolds, why don't you just make your own headers. From what I've seen on don't think it would be a problem.
You're right, I could make headers to route where I want them, but I like the idea of cast iron manifolds for durability, heat containment, and if the routing is right they are also very compact - so I'm trying to see if I can make that work with an optimal set. So far it looks like the ones shown will work pretty well. I have the engine, trans, t-case set in the frame roughly and so far so good. Will refine a bit then post some pics.
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Old 03-16-2016, 06:22 PM   #158 (permalink)
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Has anyone seen a formula to calculate how much shackle angle changes the spring rate?
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Old 03-17-2016, 10:25 PM   #159 (permalink)
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Has anyone seen a formula to calculate how much shackle angle changes the spring rate?
I haven't seen anything, but I did see a general reference of an SAE design and application manual for leaf springs, and I may try to track it down. There may be something in that on shackle effect on rate, and this discussion has my curiosity up. I'l let you know if I find anything. I'm still partial to the simplicity of leaf springs...
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Old 03-17-2016, 11:24 PM   #160 (permalink)
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Yeah I'd be curious to see if you can dig anything up. I may be wrong, probably am, but I think the diagram up above may be backwards. (That is, I believe a flatter or "less vertical" shackle corresponds to a lower effective spring rate.)

For example with a perfectly vertical shackle it should result in an 1:1 ratio; if your spring rate is 300 lb/in for instance, the instantaneous effective rate with that shackle would be 300lb/in I believe.

Now the other far extreme, if your shackle was parallel to the ground, any amount of force would cause the system to compress; effectively the spring rate would be 0 (ignoring the lengthwise forces applied to the spring, which you can't really do..).

Anyway thinking of those two extremes suggests to me that at angles in between, the more leaned over (less vertical) the shackle, it seems the lower the effective rate will be.

I played with some examples in CAD, and it seems to be consistent with this. For example comparing a 30 degree angle at ride height (30 degree from vertical) to a 60 degree (from vertical) it appears as though the 30 degree reduces the effective spring rate by around 10%, and the 60 by about 20%.

Anyway I don't want to derail this thread and I do want to recheck my numbers, but I'm curious to know the truth and/or see where I screwed up....

Since I'm sketching things anyway, could you tell me more about your springs, shackle and mounts: distances, spring length, free arch, thickness, number of leaves, claimed spring rate, etc?
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Old 03-18-2016, 12:12 AM   #161 (permalink)
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Drivetrain Positioning

Proceeded to position the engine, transmission, and transfer case in the rails. I initially set a height thinking that I might not want to push things high enough for a flat skid plate due to concern about crowding the interior. I then placed the grill, radiator and cowl/firewall assembly around it to see how things were looking. After studying this initial set -up as shown in the following pics, I'm thinking I'll make some changes in positioning. Here's where it currently sits as an initial baseline:







Here's some key dimensions on the above first pass: The engine is set level- no tilt down on the back. (In thinking back in time to when I had the stock engine, I think it was set up this way, and I always thought it was sensible in terms of driveshaft angles - so the front didn't pay a penalty to ease the u-joint angle on the back. I think it's a nice idea... IF both driveshaft angles are in a reasonable range...)

The low point on the transmission is the casting sump around the drain plug, and it sits 1.5" below the rail. The X-fer case oil pan low point is 2" below the rail. The e-brake lower edge is 3" below the rail. Everything is offset towards driver side by 1.125". The engine bay length is 36" from the front face of the grill to the firewall. This is 4" longer than stock I believe, based on some measurements I took before tear down.

You may also notice that I have the original firewall / floor transition bend sitting 1" above the rail (see wood blocks). I intend to mount the final floor directly to the rail tops, which will end up 1" lower than stock as referenced relative to the grill shell - in other words the front floor will sit 1" lower relative to the upper body outline than stock. Relative to the bottom of the rails it will be at about stock height since the 5" tall rail is offset by elimination of the normal 1" of hat channel and stock thin body mount cushion.

After staring at this set-up for a while, here's some thoughts on adjustments:
The steering shaft won't fit around the manifold with a straight shot single shaft. I like the offset overall though for front driveshaft clearance, plus I think I can also route the passenger exhaust past the x-fer case torque mount (so I don't have to go under the engine with it). Based on this balancing act, I think I may bite the bullet and add a u-joint and pillow block to the steering arrangement and keep the current offset. The routing with another joint looks pretty viable.

Estimating the intake manifold, carb, and air cleaner height, I can move way up with the engine in the tall 3B engine bay without getting into trouble. The concern I had about interior space crowding from going higher with the drivetrain isn't as bad as I had originally been concerned about.

The e-brake is a concern on several fronts. It's an inch lower than everything else on the bottom. It sticks into the passenger side interior floor under the seat, especially if I go higher. It also crowds the passenger side exhaust routing idea. Trouble on several fronts even though I dig the driveline brake concept overall. I'm thinking I may take it off and do something different.

If I take off the e-brake, then about 2" of height increase would get me to a flat skid plate, which would be pretty cool. You can also see that the drivers side exhaust manifold flange is currently kind of close to the rail corner. Setting the engine higher would provide lots more clearance here. It would also make the steering shaft routing a little easier, but would still require a middle u-joint.

I have some room to push the engine forward while still having sufficient clearance between the pump pulley and the electric fan. I think I'll move it forward about 0.5" -0.75", and shorten the engine bay accordingly. I originally estimated a stretch of 3.5" in the engine bay, and that estimate appears to be panning out.

I've got some space between the grill and radiator that will have a short front shroud. The lower side of the space is bounded by the top of the full height 2" x 5" crossmember in front of the radiator. I could have made the engine bay shorter by getting rid of this space, using a shallower cross member, and by cutting the headlight buckets to push the radiator forward, but I liked the big cross member and the overall layout this way. So most of the engine bay stretch is due to that decision. Here's pic that shows the cross member sitting between the grill and radiator. The lower edge of the radiator opening is aligned with the top of the cross member, which also centers the radiator vertically to the grill slot openings.

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Old 03-18-2016, 03:10 AM   #162 (permalink)
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Hi Jalbrecht42,

I pondered the same question, but didn't go very far with it since I had decided to aim for "neutral" 90 degree position at rest as my target -which i believe the drawing has correct.
This is a little different than "vertical" if by that you mean orthogonal to the ground. I think the 90 degree - to spring eye datum shown on the drawing makes sense as the neutral spring rate resting case. The force from lengthening of the spring is orthogonal to the shackle so that the shackle poses no constraint to the lengthening.

If I come up with a good analysis of the rate effect of tilt, I'll post an update.

On your question regarding spring dimensions and mounting geometry, here's a sketch I had done for myself to summarize my springs and some of the geometry aspects, as i was working through my frame design. It needs some explanation on a few points, which I'll list following the pic:



The drawing is for the main leaf of the pack. It also lists how many leaves in each pack.

In laying out my frame design/spring geometry, I worked with lateral distances (along the rail axis) and elevation heights perpendicular to the rail. I also calculated direct eye to eye lengths from these, but generally worked with the orthogonal dimensions as that's how I would measure and build it. On the top of the drawing you'll see YJ lateral distance from fixed to shackle hanger eyes. You'll also see a CJ3BL distance, which is the lateral distance between hanger eyes that I ended up using on my build.

There's also some notes about the stock YJ spring dimensions that I pulled from the General Spring site.

I think the General Spring site has some rate info. I don't have any info on rate for the RE springs.

There's also some notes about expected axle movement at full compression vs. unloaded spring. I was using this for some estimates to avoid the rear axle hitting the fuel tank, estimating my side bumper design, wheel openings, etc...

Some stuff that's not on this drawing, but that is on my frame drawing that might be helpful is:

The rail stack elevation at both ends is 5". The fixed hangers I made have a 2.25" eye center height from their mounting surface. The CJ rear Currie / Slick Rock hangers I'm using at both ends for the shackles have an eye center height of 0.8125" to the mounting surface. So the fixed hanger eye - to shackle hanger eye height at both ends is 6.4375". (I didn't round nominal fractional dimensions) The Currie shackles I'm using are 4.25 long eye to eye.

Hope that is of some help!
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Old 03-18-2016, 07:09 AM   #163 (permalink)
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Thanks, if I have a chance I'll take a look at this with your geometry and see what I come up with. That's a good point about measuring shackle angle relative to the line drawn through both spring eyes (as shown in the sketch up above). In my example I set the "flat" spring datum at horizontal and just measured the angle relative to vertical through travel, so this probably confuses things more.

Since you modeled your design after CJ and YJ dimensions and targeted a "neutral" shackle position at ride height your probably in great shape--I'm just trying to understand things and the above talks rekindled a question I've thought about before. Mostly because the first time I figured this out I did it on my own and everything worked great. A few years later I see that diagram and think "what? That's backwards". And then I see it over and over and over and I think "what am I missing here...?"

So why are you increasing the overall cab height by 1" (dropping the floor 1" relative to the cowl)?
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Old 03-18-2016, 07:56 AM   #164 (permalink)
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Some miscellaneous rambling....

Spring rate. There has to be a vertical component to the spring rate in regards to the shackle. If the spring is rated for say 100lbs/in, we know that for every 100lbs added, the spring moved 1". If the shackle is also swinging in a way that adds or subtracts vertical movement, that is going to have an effect on spring rate. If you compress the spring 1", but if the shackle movement also lets the axle displace vertically, then you have just lowered spring rate. The reverse should also be true. You could also get yourself into a position where the shackle has nowhere to swing, or cannot accommodate the change in spring length, which could lock the system ( or approach an infinite spring rate? ). To calculate this we would need to make an accurate model of the length/arch of the main spring leaf. We wouldn't really need to know spring rate, you could just graph the vertical displacement of the entire system vs the vertical displacement of the spring.

Engine placement. It looks like you have TONS of room to work with since you stretched the nose. If you extended the steering column length to move that steering joint down, would what help you get the steering shaft into a sweet spot where you wouldn't need to add parts? Basically lower the steering shaft towards parallel to the ground. Then sneak it between the frame and the manifold.

Jalbrecht42. I don't think he is dropping the floor, he is raising the frame. Instead of hat channels he used 5" tall frame material. He removed the spacer under the grill and bolted it directly to the rail. Then he is basically removing the hat channels and having the floor directly on top of the frame. It would be like if I added a 1" tall strap on top of my frame.
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Old 03-18-2016, 08:26 AM   #165 (permalink)
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Yeah I'd be curious to see if you can dig anything up. I may be wrong, probably am, but I think the diagram up above may be backwards. (That is, I believe a flatter or "less vertical" shackle corresponds to a lower effective spring rate.)

For example with a perfectly vertical shackle it should result in an 1:1 ratio; if your spring rate is 300 lb/in for instance, the instantaneous effective rate with that shackle would be 300lb/in I believe.

Now the other far extreme, if your shackle was parallel to the ground, any amount of force would cause the system to compress; effectively the spring rate would be 0 (ignoring the lengthwise forces applied to the spring, which you can't really do..).

Anyway thinking of those two extremes suggests to me that at angles in between, the more leaned over (less vertical) the shackle, it seems the lower the effective rate will be.

I played with some examples in CAD, and it seems to be consistent with this. For example comparing a 30 degree angle at ride height (30 degree from vertical) to a 60 degree (from vertical) it appears as though the 30 degree reduces the effective spring rate by around 10%, and the 60 by about 20%.

Anyway I don't want to derail this thread and I do want to recheck my numbers, but I'm curious to know the truth and/or see where I screwed up....

Since I'm sketching things anyway, could you tell me more about your springs, shackle and mounts: distances, spring length, free arch, thickness, number of leaves, claimed spring rate, etc?
I think this leaf spring discussion should get it's own thread so CJ3BL's thread isn't too plugged up with this. It would be nice to get this explained and discussed. I can't seem to find anything on calculating how the shackle angle effects the spring rate yet. Maybe since most people just go to coils or coilovers when they get into this not much is out there.

I've quoted the section on shackle mechanics below where I got the picture. After reading your post I went and read through the whole section a few times. It sounds like you are on to something because the second part talks about the jacking effect with the spring eye moving up and down also effecting spring rate in the opposite manner.

More information to ponder I guess...

Jeep Parts, Jeep Accessories & Jeep Soft Tops From The Jeep Parts Experts - Quadratec

Shackle Mechanics

The angle of the shackle can stiffen or soften a spring's normal rate. You can determine the effective angle of a shackle by drawing a line through the middle of both spring eyes and a line through the shackle pivots. Then measure the angle formed by the two lines (measure ahead of the shackle - see illus. 3). You can increase the effective rate of a leaf spring by decreasing the shackle angle. An increase in shackle angle will produce a decrease in the effective leaf spring rate of a leaf spring.
A good starting point for shackle angle is 90 degrees. In this position the shackle has no effect on spring rate. Keep in mind that the shackle angle changes (and consequently the spring's effective rate changes) whenever the suspension moves. Also, the shackle's angle will change whenever you change the chassis' ride height, the arch of the leaf, the load on the leaf, or the length of the shackle. Since the shackle direction changes when the leaf is deflected past a flat condition, you should avoid deflecting the right rear leaf to an extremely negative arch condition. This could cause a very large shackle angle at high loads and consequently a very soft spring rate. Excessive body roll and poor handling could result. You can correct this problem by decreasing the shackle angle, increasing the arch, of the spring by increasing the rate of the right rear leaf spring.

Shackle length is another factor affecting the rate of a leaf spring. A short shackle will change its angle (and the effective rate of the leaf spring) quicker than a long shackle upon deflection of the leaf. There is a second shackle effect on the stiffness of the rear suspension that counteracts and sometimes exceeds the shackle?s effect on spring rate. This second effect occurs whenever the shackle swings in its arc and moves the rear spring eye vertically.

The vertical movement of the rear spring eye causes a jacking effect. If the shackle movement forces the rear spring eye downward, the leaf will deflect and exert an upward force on the chassis that will add stiffness to the rear suspension. Conversely, the shackle will reduce suspension stiffness if t causes the rear spring eye to move upward during suspension travel.

The stiffening effect occurs during suspension deflection whenever the rear spring eye is ahead of the upper shackle pivot and the shackle is moving rearward (see illus. 4, example B). In this position, however, the shackle also produces a softening effect by reducing the effective rate of the leaf spring (due to the large shackle angle). The overall effect to the stiffness of the rear suspension is determined by the greater of the two shackle effects. Under opposite conditions, you can expect a reversal to the above effects. If the rear spring eye is located behind the shackle pivot (illus. 4 example A) the shackle effect will tend to reduce suspension stiffness whenever the shackle moves rearward. However, the small shackle angle will tend to stiffen the spring's rate. The overall effect to the suspension's stiffness is determined by the more dominant of the two shackle effects. Keep in mind that the movement of the rear spring eye (from its static position) is mostly forward under racing conditions.

If a leaf goes into negative arch the travel direction of the shackle changes and the shackle effects change. Handling is not consistent under these conditions.

The second effect of the shackle can be enhanced by increasing the length of the shackle. Generally, the second shackle effect (jacking)is dominant.
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Old 03-18-2016, 08:46 AM   #166 (permalink)
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Alright....lets move this leaf spring stuff over to here...

https://www.pirate4x4.com/forum/jeep-...-geometry.html
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Old 03-18-2016, 01:44 PM   #167 (permalink)
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Alright....lets move this leaf spring stuff over to here...

https://www.pirate4x4.com/forum/jeep-...-geometry.html
It's been fun, but good idea to continue with a dedicated thread. Cool!
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Old 03-18-2016, 02:35 PM   #168 (permalink)
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Some miscellaneous rambling....

Spring rate. There has to be a vertical component to the spring rate in regards to the shackle. If the spring is rated for say 100lbs/in, we know that for every 100lbs added, the spring moved 1". If the shackle is also swinging in a way that adds or subtracts vertical movement, that is going to have an effect on spring rate. If you compress the spring 1", but if the shackle movement also lets the axle displace vertically, then you have just lowered spring rate. The reverse should also be true. You could also get yourself into a position where the shackle has nowhere to swing, or cannot accommodate the change in spring length, which could lock the system ( or approach an infinite spring rate? ). To calculate this we would need to make an accurate model of the length/arch of the main spring leaf. We wouldn't really need to know spring rate, you could just graph the vertical displacement of the entire system vs the vertical displacement of the spring.

Engine placement. It looks like you have TONS of room to work with since you stretched the nose. If you extended the steering column length to move that steering joint down, would what help you get the steering shaft into a sweet spot where you wouldn't need to add parts? Basically lower the steering shaft towards parallel to the ground. Then sneak it between the frame and the manifold.

Jalbrecht42. I don't think he is dropping the floor, he is raising the frame. Instead of hat channels he used 5" tall frame material. He removed the spacer under the grill and bolted it directly to the rail. Then he is basically removing the hat channels and having the floor directly on top of the frame. It would be like if I added a 1" tall strap on top of my frame.
Meiser has it right on the mark as far as the floor height relative to the frame rail bottom, and in concept also relative to the grill/body profile per your question Jalbrecht. In fact, this back and forth made me realize that I had made a mistake on my mock up wood block height, and my initial comment of the front floor being 1" lower relative to the grill. Thanks for keeping me honest and out of trouble guys!!!

Here's how it works out:

Meiser is right on the mark on the floor height relative to the lower rail surface. It's essentially stock - as the higher 5" rail is filling the space that normally would be 4" of rail plus 1" of hat channel plus thin stock body mount pad.

Referencing distances to the grill as a datum for body heights, here's how it works out:

My old frame measured 9.8" from the lower center rail surface to the top of the grill mounting bracket. There was no cushion on this mount that I can ever remember. On the new design, the grill mounts directly to the top of the 5" stack rail, with a 0.125" rubber pad. The new height of the grill vs the center bottom rail surface is then 10.125", so the grill sits 0.325' higher relative to the frame bottom vs. stock. So, combining these two points, the front floor height relative to the grill ends up 0.325 lower than stock.

Where i goofed on my mock up is I chose a 1" wood block to get the top of the cowl roughly even with the top of the grill. But I didn't think about the web on top of the grill, or the rise of the hood hinge attached to the cowl. It's close enough for the current activity, but I'll need to pay attention when I set the final cowl and hood position.

On the steering, your thought is a good one. Currently a straight shot to the box from the original column position runs right into the front of the exhaust manifold big time. When I raise everything up 2" to get a flat bottom then I might be able to squeeze the shaft under the manifold. Possibly go with some tilt rather than level might also help, although I prefer to keep a level position if I can. (If I do manage to keep it level, I plan to use a tapered spacer to get the carb leveled out).

Thanks for the inputs!
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Old 03-18-2016, 02:52 PM   #169 (permalink)
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I wouldn't worry about the carb being not exactly level front to back. I have been running mine like that for years. No downside that I have found with my Autolite/Motorcraft 2100. Your mileage could vary with other carbs. The 2100 has the main jets right in the middle bottom of the bowl.

If your OCD kicks in, I think having the intake carb mounting surface shaved could be neat.
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Old 03-18-2016, 03:18 PM   #170 (permalink)
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I wouldn't worry about the carb being not exactly level front to back. I have been running mine like that for years. No downside that I have found with my Autolite/Motorcraft 2100. Your mileage could vary with other carbs. The 2100 has the main jets right in the middle bottom of the bowl.

If your OCD kicks in, I think having the intake carb mounting surface shaved could be neat.
Good to know! The shaved manifold would be a really clean way to go. As you can probably tell so far in my posts so far I can be pretty OCD, so that would be the kind of stuff I'd be likely to pursue. At the same time, I was thinking of adding spacer for thermal isolation of the carb, so it would be easy to shave that to level the carb. Good food for thought though as I like clean , simple, uncluttered functionality. I may pursue that when I get to that stage. Thanks!
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Old 03-22-2016, 02:52 AM   #171 (permalink)
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Drivetrain Positioning 2

I decided to go for it and move everything up 2" to see how it would work with a flat skid.

The driveline e-brake is below the rails and skid at this height, but I think I am going to take it off in order to support simple passenger side exhaust routing and a flat underside.

To move things up, I revised the temporary T-Case output mount/cross member I had made by re-welding the plate to flip it over, allowing the temp cross member to rest on top of the rails. This raised up the t-case and made it easier to move around. I then shimmed between the cross member and rails to tweak the height.

I also moved things forward a bit. The space between the water pump pulley and electric fan is now just large enough to thread a fan belt through to keep it easy to change a belt.

The offset was reduced to 1" as part of trying to get a straight shot with the steering shaft, which I had wanted but was having a hard time getting worked out at the prior lower engine height. Meiser's suggestions prompted me to try harder - thanks! Moving the engine up 2" created room under the drivers exhaust manifold, and with the reduced offset, it looks like it may provide sufficient clearance. I'll have to move the column position on the floor about 1-1.5" outward, which I think will be fine as it also provides more room for the gas and brake pedals, offsetting the crowding caused by the high transmission position. The Trans + T-case sit high in the interior, but I think I can live with that in order to get the flat skid.

The basic cross member is a straight 1.5" x 3" tube under the T-18 and the Dana 18 torque mount. The T-case torque mount is about mid-rail in height and if I used the stock style mount I would have problems with the exhaust routing, but I have a couple of design concepts worked out that will solve this. I'll choose once I have the basic cross member positioned. I'm also using a Jeep CJ T-14 trans mount that bolts to the t-case adapter. It will mount on a bracket extending back from the x-member tube.

Since the overall flat skid position is looking good, I started building the cross member. I'm thinking I may also place another cross member at the back of the t-case just under or around the output yoke if I can fit it, as this would more fully support the back of the skid and strengthen the frame.

Here's a pic of the revised engine position, with steering shaft loosely in place. This is a Borgeson collapsable shaft. I may modify it so that the area next to the manifold has the smaller diameter shaft rather than the larger double D tube - or just use a non-collapsable smaller diameter shaft since there's a good break angle at the column.



Here's some shots of the cross member build so far.
The main part is a 1.5" x 3" x 0.120" tube, with welded 0.188" end caps. On the end caps, I wanted to provide a lead-in taper on the upper half to make it easy to draw the cross member up into its mounting bracket. The frame rails currently want to bow inward about 1/8" per side due to weld shrinkage at the front and rear cross member welds that pulls the rails inward over the length between the cross members. I had temporary rail spacers in place when I made the welds and I welded in short sections and let cool, but still had some shrink. This little issue will improve when I add another cross member / torsion bar tube at the rear rail jog, plus floor bracing, etc... but the end cap lead-in taper on the cross member will make sure it slides into place with no problem. The lower half on the cap has no taper, so it butts against the rail.

I formed the end cap taper on my finger brake, and then fit and welded it to the tube ends:







Then I cut, faced, and countersunk some crush tube inserts:



These were then fitted and welded:





The cross member will bolt upward into brackets on the rails, and the countersunk allen head bolts allow the skid to mount flush to the x-member and rails. I'll need to grind the welds to make smooth contact surfaces. Rail mount brackets are up next, then the trans mount bracket, then the t-case torque mount.
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Old 03-22-2016, 02:03 PM   #172 (permalink)
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What kind of finger break do you have that will bend that, 1/8 max on mine.
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Old 03-22-2016, 03:39 PM   #173 (permalink)
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Hi Leecarr,
I've got a SWAG weld-it-yourself finger brake set up that mounts to a Harbor Freight shop press. You can see it a little in the pics on page 2 where I formed fixed shackle hangers from 0.188". Here's a link: http://www.swagoffroad.com/20-TON-Fi...-Kit_p_86.html It was pretty easy to put together, and I'm very happy with it. I also have their "Flat Top" lower die and arbor plates. The Flat Top die works well with the finger brake set-up for small parts like these end caps, and the fixed hangers. Sure better than the big hammer and vice method I was destroying parts with before I had it! It can handle heavier bends, although I've just used on 1/4" and thinner and on small parts so far.

Last edited by CJ3BL; 03-22-2016 at 03:40 PM.
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Old 03-23-2016, 05:44 PM   #174 (permalink)
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Fancy you should ask, Centerforce! I'm using a Centerforce CF700160 Flywheel, CTFC165552 Pressure Plate, CTFC281226 Clutch Disc, and N-1439 Bearing. Mix and match of GM, Ford and Jeep applications.
Awesome! We'd like to hear how it works for you once that bad boys running.
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Old 03-23-2016, 10:57 PM   #175 (permalink)
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Will do Centerforce!
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