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Discussion starter · #781 · (Edited)
Finish Removable Cowl

To wrap up the removable cowl mods, I needed to add mounting flanges at the sides.

In doing this, I decided to trim the panel to a point that would replace some warped areas around hole and dent patching I had done previously. (pics tipped sideways to show parts better)

Here's the cut, and the fitted patch panel / flange part:



After bench fitting the patch panel and flange, then it was final fitted on the rig. This made sure that the cowl matched up to both the firewall flange across the front, and the cowl supports on the sides:


One tacked, it was removed and then fully welded, and the welds rough finished. It was then mounted up again, clamped to the side supports, and then the mounting holes marked on the cowl side flanges using a transfer punch through the support mounting holes. Here's the flanges with mounting holes drilled - viewed from the underside of the cowl:



Here's the mostly finished cowl assembly, with one pic from under the dash area showing how the mounting flanges attach to the cowl side supports, and the second shows the finished flange area overall:



I'll be doing more trimming of dash side of the cowl assembly later on - after building the cage. The back ends of the cowl support tubes will be welded to the cage A pillars - where the temporary A pillar tubes are tacked currently. The dash panel will be attached between the A pillars. What currently looks like the dash panel on the cowl assembly will be cut back to make a 1" flange that will overlap the upper part of the dash- like the factory design but attaching to the dash panel with machine screws rather than spot welds.

Glad to be done with this part of the body. Took a lot longer than I expected...
 
Discussion starter · #785 ·
Clutch and Brake Pedals

I thought I'd turn my attention to driver and passenger positioning related things and figure it's about time to tackle the brake, clutch, gas pedals. I'm using hydraulic clutch with internal slave and hydroboost brakes.

In thinking through the pedal options like CJ, XJ, YJ pedals, I decided to build my own pedal assembly so I can optimize placement of the pedals, the MC's on the firewall, column placement, and pedal ratios.

For the clutch, I'm targeting a 6:1 pedal ratio, which is right in the middle of the Tilton recommended range for the Tilton slave and master I'm using.

For the brakes, I'm planning to use a Bosch booster with 1 1/8" bore chevy master cylinder, and 1971-78 Chevy 3/4 Ton Truck calipers front and rear. Most forum posts and some commercial sites like Master Power recommend a pedal ratio of 4:1 for power brakes in general, but most posts are related to vacuum assist, not hydroboost. I've seen one commercial site for pick up truck conversion kits indicate that they prefer a 5:1 ratio on their hydro boost conversions.

Is there a difference between hydroboost and vacuum assist as far as optimum pedal ratio choice?

Do any of you have a recommendation or a good reference for optimum pedal ratio for hydroboost?


Any thoughts?
 
I thought I'd turn my attention to driver and passenger positioning related things and figure it's about time to tackle the brake, clutch, gas pedals. I'm using hydraulic clutch with internal slave and hydroboost brakes.

In thinking through the pedal options like CJ, XJ, YJ pedals, I decided to build my own pedal assembly so I can optimize placement of the pedals, the MC's on the firewall, column placement, and pedal ratios.

For the clutch, I'm targeting a 6:1 pedal ratio, which is right in the middle of the Tilton recommended range for the Tilton slave and master I'm using.

For the brakes, I'm planning to use a Bosch booster with 1 1/8" bore chevy master cylinder, and 1971-78 Chevy 3/4 Ton Truck calipers front and rear. Most forum posts and some commercial sites like Master Power recommend a pedal ratio of 4:1 for power brakes in general, but most posts are related to vacuum assist, not hydroboost. I've seen one commercial site for pick up truck conversion kits indicate that they prefer a 5:1 ratio on their hydro boost conversions.

Is there a difference between hydroboost and vacuum assist as far as optimum pedal ratio choice?

Do any of you have a recommendation or a good reference for optimum pedal ratio for hydroboost?


Any thoughts?
Off the top of my head, those pedal ratios sound incredibly low. I would try and measure a few factory vehicles to see the rough range. I don't remember that a hydroboost vs vacuum assist system would have a different pedal pack assembly in the same vehicle.

It is worth noting that the actual stroke at the piston is really important too. That can change packaging with any pedal ratio a lot.

The 3B cowl height should be a no-brainer for pedal length really. I would plan on having both of the swing-arms outside of the steering column to allow enough room for your accelerator foot. The space in there gets tight with the go pedal quick. Getting the clutch master to fit can be a challenge, but the hydroboost should package a little better
 
Discussion starter · #787 · (Edited)
Hi Meiser-
Thanks for your thoughts on this! On the ratios, could you be recalling manual brake pedal ratios, which run higher?

The tech section Bill Vista brake article here on Pirate is really helpful and consistent with other info I've found and measurements I've made. Manual brakes and clutch master cylinder pedal ratios usually run between 5 and 7:1. I think folks with a manual MC and discs tend to go towards the 7:1 number to be able to push a bigger bore cylinder that moves enough volume for the disc calipers.

Vacuum assist power brakes are typically lower. The Bill Vista article cites a typical range for power brakes between 3 and 4:1, while others cite typical between 4 and 5:1. There's less mechanical advantage needed from the pedal given the vacuum assist, so the ratio can go lower, and the MC bore can go larger to move more fluid - which is nice for disc calipers. The Bill Vista article has a nice section on his instal of a Vanco hydroboost- but I didn't see info on pedal ratio used.

Great point about whether vacuum and hydro use the same pedal assembly in a given vehicle type. I might be able to compare a diesel/hydro vs gas/vacuum truck model to see if there's any difference in pedal set-up. Excellent idea!

Agreed on the piston stroke consideration (and pedal stroke). I think I have a handle on that part.

The extra height on a 3B firewall is definitely a help! On the other hand, I've jammed the engine up pretty high to get a flat belly and the valve cover PCV valve is a concern for clearance. On the clutch MC, I've also been hoping to not place it too high so I can utilize the extra 3B firewall height to run engine compartment roll cage bars from the top firewall corners to a hoop behind the grill- to hang the front shocks from. Will see if I can make that work... Lots of trade offs in packaging even with more space!
 
Hi Meiser-
Thanks for your thoughts on this! On the ratios, could you be recalling manual brake pedal ratios, which run higher?

The tech section Bill Vista brake article here on Pirate is really helpful and consistent with other info I've found and measurements I've made. Manual brakes and clutch master cylinder pedal ratios usually run between 5 and 7:1. I think folks with a manual MC and discs tend to go towards the 7:1 number to be able to push a bigger bore cylinder that moves enough volume for the disc calipers.

Vacuum assist power brakes are typically lower. The Bill Vista article cites a typical range for power brakes between 3 and 4:1, while others cite typical between 4 and 5:1. There's less mechanical advantage needed from the pedal given the vacuum assist, so the ratio can go lower, and the MC bore can go larger to move more fluid - which is nice for disc calipers. The Bill Vista article has a nice section on his instal of a Vanco hydroboost- but I didn't see info on pedal ratio used.

Great point about whether vacuum and hydro use the same pedal assembly in a given vehicle type. I might be able to compare a diesel/hydro vs gas/vacuum truck model to see if there's any difference in pedal set-up. Excellent idea!

Agreed on the piston stroke consideration (and pedal stroke). I think I have a handle on that part.

The extra height on a 3B firewall is definitely a help! On the other hand, I've jammed the engine up pretty high to get a flat belly and the valve cover PCV valve is a concern for clearance. On the clutch MC, I've also been hoping to not place it too high so I can utilize the extra 3B firewall height to run engine compartment roll cage bars from the top firewall corners to a hoop behind the grill- to hang the front shocks from. Will see if I can make that work... Lots of trade offs in packaging even with more space!
At least on gm trucks there is a slight difference in the pedal ratio for hydro/vac. Brakes. Wish I had some pedals here but I think they are all in storage otherwise I’d measure for you.

Edit: found two but it might be apples to oranges because of year differences.

Pedal 1 is out of an ‘05 Silverado w/vac. Brakes

15” pivot to center of pad, 3 1/16” pivot to center of pushrod

Pedal 2 is a ‘98 3500 hydro brakes

15” pivot to center of pad, 2 5/16” pivot to center of pushrod
 
Discussion starter · #789 ·
Thanks Twankie! I really appreciate that you made the measurements. Really useful info!

Pretty interesting that the hydro is a high ratio at 6.5 - similar to a manual brake pedal set-up. Even if different years and not a direct side by side, it's very interesting that the hydro ratio is that high.

The vac assist ratio of 4.9 on your pedal set is about the same as a YJ I think. I did some measurements from a head-on pic of a YJ pedal set, and it came out at 4.8 as best I could measure from the pic. Looking for one I can measure directly.

Not clear why a hydro would use a different ratio that vacuum assist, but it would actually make life easier on the pedal layout if the brake and clutch were comparable ratios instead of the 4:1 brake and 6:1 clutch combination I have been thinking of initially. I plan to have the pedals pivoting from a common shaft as in the usual designs, so similar ratios would simplify things.

Thanks so much!

Any other hydro insights out there?
 
Discussion starter · #790 · (Edited)
Hydroboost pedal ratio continued...

Twankie's measurements comparing GM truck hydro vs vacuum pedals on different year GM trucks, plus Meiser's comment to look at comparing vacuum vs hydro pedals on the same vehicle type got me headed in a fruitful direction. It's looking like hydro works better with higher pedal ratios than vacuum assist. I had thought that hydro would use ratios comparable to vacuum power brakes- especially since it creates even greater pressures.

I'd been looking at Jeep and hot rod info on hydroboosts, but hadn't looked specifically at GM truck conversions. That should have been an obvious thing to do, but it took Meiser and Twankie's inputs to point me in that direction. Thanks! Several posts on GM truck sites cite swapping the brake pedal as part of the hydro conversion. GM used two different pedals - the pedal ratio on the stock GM pedal for hydro is higher than the pedal for vacuum.

One really good post is here:
https://www.gmfullsize.com/threads/hydroboost-install-how-to-with-pics.156800/

It's a conversion of an 04 Silverado using hydro parts from an 06 Tahoe.
It includes a great side by side photo of the pedal comparison. Measuring relative lengths in the photo for pivot to pedal center pedal length and pivot to push rod pivot center length, the hydro appears to be about 6.8:1, while the vacuum assist is 4.1:1 Very similar to the more accurate 6.5 hydro pedal ratio from Twankie's direct pedal measurement.

Another post indicates that the pair of vacuum and hydro pedals are consistent across models years 88-94, and another pair run from 96 and up- so Twankie's comparison measurements between 98 and 05 models should reflect just the vacuum vs hydro difference.

I had also mentioned the Bill Vista Vanco hydro article in the Pirate tech section in a prior post. On re-reading that, it became clear that he converted from manual to hydro, with no change in pedal ratio. This also supports the idea of higher pedal ratio for hydro.

Lastly, this hydro conversion kit for 50's GM trucks has an interesting statement on preferred pedal ratios for hydro being between 5 and 6:1
https://westernchassisinc.com/1955-59-Chevy-Truck-HydroBoost-Hydraulic-Brake-Assist-Kit/

I'm targeting the clutch pedal ratio to be 6:1 based on Tilton specs. With this new info on hydro pedal ratios, I'm thinking 6:1 may be a good choice there too. Will work through the geometry of the layout and see how pedal throw works out. The long pedals needed to mount the cylinder high on firewall to clear valve cover, while keeping them at a reasonable height to the floor may have a pretty long throw. Need to see how it lays out. The clutch pedal throw works out OK at the 6:1 ratio, but its MC stroke is shorter...

I still haven't found a good explanation of why hydro would use a higher ratio than vacuum assist. May geek out and try to learn some more...
 
Discussion starter · #791 ·
Learned some more...

Too satisfy my curiosity, I bought and downloaded a copy of an SAE (Society of Automotive Engineers) paper, SAE 730536 "Hydraulics Offer Advantages in Power Brake Boosters", by Brown, Bach, and Baker of Bendix Corp. from 1973. The Bendix hydroboost design in common usage is now made by Bosch. After reading the paper, I think I now understand the pedal ratio topic that was eluding me. It's also a great read as far as understanding how hydroboost works.

Inside the boost unit is a "ratio lever" whose function results in an effective power assist output ratio that is lower than the mechanical pedal ratio. While the effective power ratio lowers, the total master cylinder output pressure achieved goes way higher than manual operation or vacuum assist. The specific design discussed in the paper has a ratio such that a 6:1 no-power mechanical pedal ratio produces an effective power ratio of about 4.3:1 - ie the same as the pedal ratio typically found in front of a vacuum assist pedal set-up. This seems reasonably consistent with the GM side by side pedal comparison above, so the example data in the paper is probably representative of the current product.

(If you look at the Bill Vista Tech Vanco hydroboost article here on Pirate, it has a hydroboost exploded view. The "lever" is on the left in the pic)

Geek curiosity satisfied, I'm forging ahead with a 6:1 target for both clutch and brake pedals, and will see if it works OK within the other packaging constraints.
 
Discussion starter · #792 · (Edited)
Brake & Clutch Pedal Assembly

Spent a bunch of time making a brake and clutch assembly. I did some drawings first to firm up the design before fabbing parts as there were a lot of little details to work out so the arms have enough travel, match the master cylinder strokes, pedals end up at the positions I want, etc...

I'm happy with how it turned out so far. Here's the assembly at this point, in a sideview:




The pedal pads will get welded on after I double check side to side foot clearance with the gas pedal I'm making. After that I'll mount everything on the firewall. The front of the assembly will bolt to the lower flange of the dash - I'll be adding dash mounting points and an upper steering column mount to the pedal box frame later on.

Here's some shots of the major pieces. The first has the box frame right side up, the second views it from the bottom.

Some specifics are : The "box" is all 0.120" flat stock, with formed bends at the front corners, and welded center section and top plates. One top plate has a threaded insert that I made for the clutch pedal travel stop ( to avoid overextending the clutch MC). The other top plate has a hole for mounting a jeep stop light switch.

The shaft is a 5/8" linear bearing shaft from McMaster Carr. It has a 3/8 threaded end on it. It's a stocked part and is a really high quality piece for the price. I also picked up their high load SAE bushings to fit the shaft, and that have a 0.750" OD to fit inside 1"OD x 0.120" wall DOM tubes. They are like bronze oilite bushings but have some iron added to withstand higher loads.

The pedal arms are 5/16" thick 1018 CR. The clutch has a 2" offset bend, the brake has a 1" offset bend. Both will be positioned to the outside of the steering column to make enough room for the gas pedal next to the transmission tunnel.

Both arms are 16" long from pivot to pedal center, and have a pedal ratio 6:1. The clutch MC has a stroke of 1.1", while the brake MC has a stroke of 1.5". The shape of the arms is the same except at the push rod pivot- which is slightly different on each to best position the pivot point for the different MC strokes- starting from the same "up" pedal position. When positioned on the firewall, the back side of the arm shape should follow the firewall / foot well slope with 3/4" - 1" clearance when the pedal is fully depressed. (the firewall - floor angle transition is lower on mine than stock- to provide more pedal clearance)





Here's some detail pics on how the shaft mounts in the box frame. The box frame is drilled to 5/8" on all of the shaft mounting holes, so the force of pressing the pedals is bearing on the full shaft diameter- not on the smaller 3/8" threaded section. On one side of the frame there's a 1" OD x 3/8" ID x 1/4" thick washer I turned- welded to the side plate. The 3/8" threaded section of the shaft holds the shaft in place laterally at this washer/pocket. I ground two flats on the opposite end of the shaft to fit a 1/2" wrench to enable the securing nylock nut to be tightened.





The last assembly step was to weld the pivot tubes in the pedal arms. I fit up the shaft, pivot bushings/tubes and pedal arms in the box frame to do final positioning. The master cylinder pushrods will use clevis fittings from Speedway, and I wanted to make sure that the pedal arms they mount to were well centered and not tilted or twisted over the mc mounting holes. With everything clamped in position, the pivot tubes were tacked to the pedal arms- in a few places I could reach. Then the pedal arms and pivot tubes were removed, tacked more fully, and final welded.

I wanted to minimize the potential for any tilt of the tubes from weld shrinkage, to assure good pushrod alignment and pedal positioning. Here's a pic of the fixturing approach I ended up using. Two square fixture blocks were bolted together lightly to secure the tube between them, and the pedal arm was clamped level on top of them, perpendicular to the tube. (The flat plates underneath the arm provide clearance to the fixture blocks for the tube welds on the underside). I welded short sections, repositioning the arms before each weld segment so the fixture blocks would oppose tilt of the tube from shrinkage during each weld. Worked out well. The tubes are very perpendicular to the arms after welding. Phew!



Here's another shot of the finished assembly:



Next up I'm making the gas pedal, will check the fit of all the pedals, then mount them to the firewall. Will also pick out some return springs and drill holes in the pedal arms and box frame to mount them - once I see how the whole thing sits under the dash.
 
I am sorry I have missed this build thread. And glad to know there are others that are taking a LONG time to get our projects done. I am appreciating the detail in the thinking, the build, and the write up. WOW! And having a few pro's following always helps in minimizing the re-do's. Cheers.

I have a IFS/IRS build going...for some time now... and am appreciating heims and omniballs to solve a lot of the issues we fight sometimes...Like your windshield attachment. I believe your theme is "relatively stock" so I get it, but a perfect place for a small omni. The "COM" series has narrow races so they might not look too much out of place. They can have 6* of offset. Just a thought as that was a real drill to get that item done.

For many years I have been using, which look like, rear tail gate hinges for the hood. This allows me to easily take the hood off when lifted 90*.. I also use that idea for the grill so it comes off quick with the radiator attached. All this is to change motors and torque converters quickly between the dunes (500hp) and the trail (250hp). It takes about two hours bolt to bolt. But I usually fix or modify something every time.......

Now I am thinking the use of omni's and heims for everything hinge. It seems over the years the rigid hinges just keep breaking sheet metal. LowRange makes some Suzuki door hinges that I am going to give a try. I don't know if they would fit your look but just wanted to throw ideas out there.

In the 70's we continually broke the sheetmetal at the stock centered hood hinges. I am sure it was from frame and body flex. We helped that by sandwiching in larger sheetmetal under the hood and dash to spread the load. Adhesive and tack welding before body painting. In '80 I did my total rebuild with the other hinges and included the wider plates. Now 20 years and cheers!

Keep up the awesome work! Don't get in any rush.......You have the other driver for now. Cheers and following. (I have no build thread..it would be 20 years...but coming soon. I am not sure I could come to this threads standard.)


Suzuki Samurai Billet Aluminum Door Hinges by Low Range Off Road (SEB-LRADH)
 

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Discussion starter · #796 ·
Thanks for your nice comments and great ideas ISDTBower! I've enjoyed reading your posts in a number of the other threads here! I especially enjoyed your contributions on Meiser's "build a willys body" thread. Great info on your work with aluminum on your rig!

I thought about conventional Heim parts for the windshield pivots, but thought they would look a little out of place - just as you figured. The alignment issue was a real challenge on that and I like your idea of using more pivoting parts like heims to replace conventional single axis hinges. Interestingly, the hood I pulled the rear brace from for this project had cracks starting in the sheet metal near the hinge, just as you described...

I'm not familiar with the Omni joints you mention, and the Com version you describe sounds like it would be great. Do you have a link to info, or are they known under another name? I'm familiar with Heims, Johnny Joints, and some variants, but not aware of Omni's. I did some Omni / Com search but search mostly raised links for ball joints on a Dodge Omni and a wood joinery product called an Omni-Joint. Would appreciate more info.

I like your hood hinge idea, and your whole concept of being able to do a fast engine swap. That's amazing! The Suzuki replacement door hinges are really cool! Where are you thinking you'd use them at? Hood? Doors? Tailgate? Nice design.

Thanks also for the admonition to not rush. I'm pretty slow, and sometimes feel like I should tip the balance more towards getting it done faster. I'm learning as I go and want to do the best work I can within reason along the way. I appreciate your reinforcement to keep going in that direction!
 
Sorry for the "name" confusion. Rod Ends and Spherical Bearings are the correct Industry names.

Spherical bearings are what are inside a "Heim or "Rod End" Body.

For a given bore diameter the outside body diameter will depend on how much misalignment is allowed before a rod in the bore would strike the outer race.

There are all kinds of games you can play with this depending on how you engineer the bushings on either side of the individual Spherical.

A spherical that may have a design limit of 18* may be pushed to over 45* with the right sizing and correct misalignment bushings.

For my trailing arm IRS i Used a 1.5" GEZ Spherical bearing for strength. It is design limited to 6* misalignment but TMR customs in Canada made me some misalignment bushings to get me 10* with a 1" thru bolt. (If that bolt breaks the whole back of the car would be destroyed!) The GEZ series Spherical Has the smallest OD to fit into the aluminum bore of the aluminum arm. It is also Teflon Lined. But $$$$$. But solved a problem. I just happened to stumble onto that bearing but find that the bearing houses all knew about them and other options.

I mention the amount of misalignment as it can dictate the overall size of the bearing or rod end. Your windshield, doors, hood, tailgate all would be minimal misalignment...and probably need minimal hoop strength to keep things small. A FK Bearing catalog is a great place to reference.

This is a whole technology you learn or taught when designing the new articulating suspensions. I think once you make the step to Spherical bearings or Johnny Joints, etc. Then you should be free to use them, appropriately, on the body.

COM8 Bore .5000 O.D. 1.000 Width .500 Mis Angle 9.5*
WSSX-T .5000 1.000 .625 9*
GEZ .5000 .875 .437 6*

It seems today we can do about anything...In the eye of the beholder.
 
Discussion starter · #799 ·
Thanks for the additional info ISDTBower and csutton7! Great stuff.

ISDTBower- your comparison of dimensions on the COM, WSSX-T, and GEZ spherical bearings and discussion of angular motion range versus size is really enlightening. I can see your point that the example windshield pivot application has a very small misalignment range needed, and doesn't need to be very strong so can be very compact in dimensions. That's cool. Your IRS is sure at the other extreme. Would love to see a pic of what you've designed on that set up! I'll check out the FK Bearing catalog you mention. Sounds like a great place to dig, learn more, and contemplate where they could be put to use!

csutton7- thanks for making the connection on the OMNI term- I can see the similarity of the omnidirectional rollers and spherical bearings.

Thanks for filling me in - always great to learn more! This rig will be pretty traditional with leaf springs, but will have some small spherical bearings for the sway bars, and shock mounts and I can sure see how they could work well in other locations too. Even though this build is taking a long time, I also like to contemplate what the next build project could be... and I like the idea of a light weight build with linked suspension, so nice to learn more about this rod end/ spherical bearing stuff!
 
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