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Re: Manual brake conversion
#21
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HH56
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Quote:
The plan is to mount a modern booster and dual circuit master under the floor like hotrodders do. In order to achieve this, I need the rod going towards the back of the car, not the front.

This was discussed a few years ago during some of the BTV replacement threads but don't recall any posts of someone ever trying it. In addition to modifying the original pedal there was also some thought of using a modern weld or bolt in hot rodder pedal and booster assy under the car instead of trying to modify or source another pedal and then still need to do the other mods. http://www.abspowerbrake.com/maincatalog_frameset038.html

In addition to TL clearance issues on 55-6 models another issue that caused some concern with the under floor setup is that by the time the assy is put together most of the modern boosters capable of stopping Packard's weight will have a height of 8" or more. The 51 and later frame rails are only around 5 1/2 or 6" high so unless some work is done in the floor pan to accommodate the diameter that could be hidden under the seat it would mean a portion of the booster will hang under the frame unprotected and vulnerable to road debris. On that ABS page there is a mini booster unit at 6" but the question on that unit was the small booster strong enough to stop a 2 ton car.

EDIT: One other thought was on PS cars the hydroboost unit could be used. One or maybe two firewall mounted hydro assy units are on pre 12v cars with a new higher mounted pedal but none have been under the floor that I know of. There are probably 6 of the electro boost units installed on the 12v models.

Posted on: 4/27 12:32
Howard
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Re: Manual brake conversion
#22
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Chris R
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Quote:

HH56 wrote:
Quote:
The plan is to mount a modern booster and dual circuit master under the floor like hotrodders do. In order to achieve this, I need the rod going towards the back of the car, not the front.

This was discussed a few years ago during some of the BTV replacement threads but don't recall any posts of someone ever trying it. In addition to modifying the original pedal there was also some thought of using a modern weld or bolt in hot rodder pedal and booster assy under the car instead of trying to modify or source another pedal and then still need to do the other mods. http://www.abspowerbrake.com/maincatalog_frameset038.html

In addition to TL clearance issues on 55-6 models another issue that caused some concern with the under floor setup is that by the time the assy is put together most of the modern boosters capable of stopping Packard's weight will have a height of 8" or more. The 51 and later frame rails are only around 5 1/2 or 6" high so unless some accommodation is made in the floor pan to accommodate the diameter and could be hidden under the seat it would mean a portion of the booster will hang under the frame unprotected and vulnerable to road debris. On that ABS page there is a mini booster unit at 6" but the question on that unit was the small booster strong enough to stop a 2 ton car.


Thanks Howard! I hadn't even thought about the clearance issues involved with mounting a booster under the floor. Having something come up and take out the brakes definitely wouldn't be good.

So, as of right now, it sounding more and more like just doing manual brakes might be the best choice.

The biggest issue that I see right now is mounting the pedal its self. On these cars the manual pedal mounted right between that "V" section of the frame. Using the factory parts would be nice because everything would just bolt into place. The rod and master setup would be easy to add afterwards.

I'll get under the car today and see exactly what I'm dealing with in regards to room.

Thanks again!

-Chris

Posted on: 4/27 12:56
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Re: Manual brake conversion
#23
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Chris R
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So, I got under there yesterday and had a look. I think the reason the aftermarket pedal hasn't been done is because it would be very difficult.

The issue is space and the triangulated frame section in that area. The brake pedal mounts right between it and its very tight.

I found the attached images from an old ebay listing. You can kinda see what I'm talking about. Keep in mind, the frame wall that the linkage passes through has been cut away and is missing.

I think my best bet at this point is to find a 55+ torsion setup and go from there. Hopefully finding these parts isn't super difficult.

EDIT: I just realized that the tags in the images say 52-54, but the brake linkage is pointing towards the rear and the pedal tab that the linkage mounts to is on the bottom. I'm guessing this was really a 55+ torsion setup?

-Chris

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jpg  s-l1600 (3).jpg (284.75 KB)
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Posted on: 4/28 9:40
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Re: Manual brake conversion
#24
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HH56
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Can't see the bottom of the brake pedal very well to say for sure which year it is but with the rod extending backward you are probably correct at 55-6 You can compare pedals in the parts manuals. Plates 62-63 in the 51-4 manual and plate 13C in the 55-6.

Posted on: 4/28 10:07
Howard
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Re: Manual brake conversion
#25
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Chris R
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Quote:

HH56 wrote:
Can't see the bottom of the brake pedal very well to say for sure which year it is but with the rod extending backward you are probably correct at 55-6 You can compare pedals in the parts manuals. Plates 62-63 in the 51-4 manual and plate 13C in the 55-6.


Hey Howard,

Yeah, it is kind of hard to see in the pictures. I've reattached the one where its easiest to see, but circled the area in red. It's still really dark but hopefully it helps.

It looks as though the plate is underneath the pivot area which I believe would push backwards if the pedal was pushed forwards.

I imagine the 52-54 plate is above the pivot point which would push forward as the pedal was pushed forward.

Thank you for the part numbers. I'll have to continue to do some digging.

-Chris

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Posted on: 4/28 10:34
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Re: Manual brake conversion
#26
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Chris R
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So, I've been doing some research on getting rid of this Treadle-Vac setup and ran into an article on lowrider.com of all places. It details a disk brake conversion on what looks to be an old Pontiac with the same setup as our cars.

The master cylinder setup is the same unit that Howard mentioned previously. In the attached images, you can see a pivot type mechanism that looks to change the ratio away from 1:1. So, I got to thinkin, I wonder if we could use just that mechanism with a manual dual circuit master cylinder and make everything really easy.

I gave them a call and ran everything by them, the gentleman on the phone confirmed that the piece I'm referring to maintains a 4:1 ratio. He then went on to tell me that I didn't need that part if I went with a manual master cylinder. He said that ratio was only needed with a power assisted setup, and that the 1:1 would be fine for a manual master.

I asked him how it would be possible with the 1:1 ratio. He went on to say that if you find the right master with the right bore size, it wouldn't be an issue. I did go on to ask him if that part was available for purchase anyway, and he said it is and he "thinks" its around $160.

What do you guys think? Is retaining a 1:1 ratio with a manual master possible if we change to a different bore size?

-Chris

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png  ABS Power Brakes 4.png (1,617.39 KB)
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Posted on: 4/30 15:02
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Re: Manual brake conversion
#27
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HH56
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That appears to be the Electroboost system and a few have been installed on 55-6 models at the factory location and 1:1 ratio with the boost power set near maximum. I believe those master cylinders were all 1". If you go that route on a 53 you would need to convert to 12v and I cannot help but wonder with the low ratio about how well the brakes work if the boost unit failed. To the best of my knowledge no one using the 1:1 ratio has tried disconnecting power to simulate a failure or if they have, did not post the result.

I and several others would much like to see what would happen with a 3/4" or smaller cylinder at the 1:1 ratio. I don't remember the exact ram size in the BTV but think it is around 5/8". It can have a longer almost 4" stroke to displace or force fluid out of the cylinder in sufficient volume to fill the cylinders whereas a modern master cylinder has a comparatively short stroke large diameter piston and quickly pushes a fair amount of fluid ahead of the piston. If the brake shoes are adjusted properly not much volume is needed but discs and poor adjustment would need more. That is where the safety margin question of how much stroke for the reduced diameter cylinder is available to move the equivalent amount of fluid. Most modern boosters and cylinders seem to have a max stroke no more than about 1 1/2 - 2 inches

Posted on: 4/30 15:26
Howard
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Re: Manual brake conversion
#28
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Chris R
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Quote:

HH56 wrote:
That appears to be the Electroboost system and a few have been installed on 55-6 models at the factory location and 1:1 ratio with the boost power set near maximum. I believe those master cylinders were all 1". If you go that route on a 53 you would need to convert to 12v and I cannot help but wonder with the low ratio about how well the brakes work if the boost unit failed. To the best of my knowledge no one using the 1:1 ratio has tried disconnecting power to simulate a failure or if they have, did not post the result.

I and several others would much like to see what would happen with a 3/4" or smaller cylinder at the 1:1 ratio. I don't remember the exact ram size in the BTV but think it is around 5/8". It can have a longer almost 4" stroke to displace or force fluid out of the cylinder in sufficient volume to fill the cylinders whereas a modern master cylinder has a comparatively short stroke large diameter piston and quickly pushes a fair amount of fluid ahead of the piston. If the brake shoes are adjusted properly not much volume is needed but discs and poor adjustment would need more. That is where the safety margin question of how much stroke for the reduced diameter cylinder is available to move the equivalent amount of fluid. Most modern boosters and cylinders seem to have a max stroke no more than about 1 1/2 - 2 inches


I don't want to go with the 12v Electroboost setup. If you look at the pictures I attached in my last message, you can see that they have a mechanism between their Electroboost master and the floorboard. That mechanism changes the 1:1 ratio to 4:1.

When I asked if I could use just that mechanism with a manual master cylinder, he said I wouldn't need to change the ratio. He said the stock 1:1 ratio would be fine with a manual master cylinder if I change the master bore size to account for the 1:1 ratio.

-Chris

Posted on: 4/30 15:54
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Re: Manual brake conversion
#29
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HH56
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Question I have is where are you going to mount and what type pedal? If there is enough room and you mount in the engine compt down toward the original location and adapt to use the bottom of the original PB pedal that will be 1:1 and converted by the new mechanism to 4:1. If you mount up higher near the air vent and connect to the pedal arm that might not provide enough stroke the way the stock pedal assy is suspended. If you install the 55 manual pedal and mount under the floor that will be around 6:1 and you would not need the extra linkage in the new bracket.

Posted on: 4/30 16:29
Howard
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Re: Manual brake conversion
#30
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JeromeSolberg
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You can think of the master cylinder/slave cylinder relationship as a lever, with the lever ratio being the ratio of the areas. The smaller the area, the larger the pressure, but you have to make that up with a long stroke, just like in a long lever arm.
The Bendix Treadle-Vac has a 0.652" (some say 0.655") bore diameter, with a very long stroke, from what I can measure around 3". This is what allowed it to work with the small diameter vacuum booster, and be (marginally) acceptable in the case one lost vacuum.

I tried a Ford Courier dual master cylinder with it's 7" booster. It has a 3/4" bore size. The 7" booster barely fit down there, but all in all the installation looked great. I put some pictures up somewhere on another thread, I need to find it.

However, the pressure ratio is proportional to the square of the bore diameter (area=pi D^2/4) that means it has a pressure ratio of (0.655/0.75)^2 which comes out to about 75% of the original brake pressure.

It was NOT ENOUGH! I drove it and I had to push HARD on the pedal, and my neighbor was of the opinion it was not safe.

I have recently evaluated using the Wildwood TM1 externally mounted dual master cylinder. It has a 0.625" bore, but only a 1.3" stroke, so I don't think it would be acceptable, though I have thought about it.

Wilwood TM1 Master Cylinder, 0.625" bore

Posted on: 4/30 21:16
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