Hydroboost Installation question

[ntsqd]

Thanks for the solid math, makes sense.

Are you saying the Vanco unit didn’t have much vertical angle but had a fairly substantial horizontal angle (between the LOA of brake pedal and the LOA of hydro? If so, any idea of how big an angle?

That would be interesting with what he told @toddz69 previously.

The push-rod from the pedal into the rear of the H-B unit has an offset at the hole for the pin on the pedal. The centerline of the push-rod's shaft is pretty close to horizontal, but the pin is below that centerline,

 

[toddz69]

The push-rod from the pedal into the rear of the H-B unit has an offset at the hole for the pin on the pedal. The centerline of the push-rod's shaft is pretty close to horizontal, but the pin is below that centerline,

Battle Born has this kit for the 80-83 trucks that has the offset pin hole in it that might be similar to what you have?

https://www.battlebornbrakes.com/pr...0-f350-hydroboost-brake-booster-upgrade-hb151

Todd Z.

 

[ntsqd]

If that isn't the same push-rod, it is very close.
Ever since seeing it I've wondered why? Clearance and fitment concerns, sure, but the force's LOA is still at a significant angle. Maybe it was the only way to get here from there? That, and mine, both appear to be production parts, not customish aftermarket parts. So there's an OEM application out there somewhere where that force LOA is acceptable.

In any case, it is an example that the pedal force LOA isn't maybe as critical as we've been lead to think. Even those trucks that get driven a lot likely still won't rack up the annual miles of an appliance* vehicle. The constraints that bind an OEM's design decisions may not need to be so stringent here.

(* credit where due, Lars was the first to use that term for a DD/family truckster/easily replaced vehicle.)

 

[jamesroney]

I'd have to go dig around on Rockauto to see the exact years but I think they started around '93 and ran until the early 00s?

Todd Z.

Yeah, it kinda depends on what you package as a Hydroboost.

If you include the firewall bracket as part of the booster, then the split goes:

1990-93 Astro Van. -Small eyebolt actuator pin. Flat plate with big nut.
1994-95 Astro Van. Large eyebolt actuator pin. Flat plate with big nut.
1996-02 Astro Van. Large eyebolt actuator pin, Formed angle plate with big nut.

 

[Yeller]

Only place I’ve seen that offset on a bunch of aftermarket stuff. Some of the Dodge HB use something similar too.

 

[ksagis]

If that isn't the same push-rod, it is very close.
Ever since seeing it I've wondered why? Clearance and fitment concerns, sure, but the force's LOA is still at a significant angle. Maybe it was the only way to get here from there? That, and mine, both appear to be production parts, not customish aftermarket parts. So there's an OEM application out there somewhere where that force LOA is acceptable.

In any case, it is an example that the pedal force LOA isn't maybe as critical as we've been lead to think. Even those trucks that get driven a lot likely still won't rack up the annual miles of an appliance* vehicle. The constraints that bind an OEM's design decisions may not need to be so stringent here.

(* credit where due, Lars was the first to use that term for a DD/family truckster/easily replaced vehicle.)

I’ve been thinking about this one a bit, I actually don’t think offset linkage creates a side force and is why they build it with the offset (specifically to avoid the side force on the hydro)

I’ve drawn it a few times to noodle on it and end up at the same conclusion.

Am I missing something in my crappy drawing?

 

[Oldtimer]

So I’m going to say that this kit has some great potential. After swapping the new ratio bellcrank, I have an acceptable solution.
I bought a $200 bracket, a $50 Astrovan hydroboost, and a $50 Amazon Raybestos master cylinder.
Also built a few hoses, and borrowed a Saginaw pump reservoir. And some -AN fitting adapters.
Aside from the 16 hours of machining, welding, and rework…it came out OK.

So, @jamesroney , will I be disappointed with the un-modified $200 bracket, Astrovan hydroboost, and a Camaro 1.125 master cylinder pushing stock 77 D44 calipers and 11X1-3/4 rear drums?

 

[jamesroney]

So, @jamesroney , will I be disappointed with the un-modified $200 bracket, Astrovan hydroboost, and a Camaro 1.125 master cylinder pushing stock 77 D44 calipers and 11X1-3/4 rear drums?

I have an extra one here for you. You’ll like it just fine.
You can drive my Boxwood one of you want. That will tell you.

 

[Oldtimer]

Is extra one modified? If yes, Sold
What is the part number of hydroboost you used?

 

[jamesroney]

Is extra one modified? If yes, Sold
What is the part number of hydroboost you used?

The extra one is un-molested.

There was an error on a mounting hole on my first one, so the eBay vendor gave me a second one. I ended up fixing the first one, and bought the additional parts to complete the kit.

92-96 astrovan HB. (Yeah, I know there’s an actuator pin diameter revision in 94…but the bellcrank comes with both bushings.)

 

[Oldtimer]

I already have an un-molested bracket.

 

[Oldtimer]

Taking some rough dimensions from my original 77 Bronco power brake bracket the ratio is 1.58 in the 1.66 to 1.75 range. I will post a more accurate ratio when I remove it and can get actual measurments.

I put 4.5 degrees of angle into the bellcrank support stand. This aligned the pedal lever with the firewall hole. I had to bend the levers to match.

Bending the levers was to align them with the center line of the clevises?

I will try the ebay bracket as delivered, but probably will remake the bellcrank to be closer to ratio of 1.5.
This would require adding 10.5 degrees of angle to the bellcrank support stand, and moving the levers along the pivot to center them with the clevies.

*EDIT: Added actual dimensions

 

[ksagis]

Taking some rough dimensions from my original 77 Bronco power brake bracket the ratio is in the 1.66 to 1.75 range. I will post a more accurate ratio when I remove it and can get actual measurments.


Bending the levers was to align them with the center line of the clevies?

I will try the ebay bracket as delivered, but probably will remake the bellcrank to be closer to ratio of 1.5.
This would require adding 10.5 degrees of angle to the bellcrank support stand, and moving the levers along the pivot to center them with the clevies.

1.66 to 1.75 seems high to me, unless Ford changes the pedal ratio on the brake pedal too.

My stock manual brake pedal was 6:1 and always assumed they didn’t change that and instead changed the overall ratio with the geometry in the bellcrank.

Do you have the pedal that goes with the factory 77 bracket by chance that would can tell us what the pedal ratio is?

 

[toddz69]

My stock manual brake pedal was 6:1 and always assumed they didn’t change that and instead changed the overall ratio with the geometry in the bellcrank.

That is correct.

Do you have the pedal that goes with the factory 77 bracket by chance that would can tell us what the pedal ratio is?

I replaced my stock brake pedal with a '76-'77 pedal years ago on my truck - they have the same pedal ratio.

Todd Z.

 

[ksagis]

@Oldtimer, a ratio of 1.5 would give you a pedal ratio of 4 which seems fine to me. (I would have gone lower than 5 when I modified my pedal but didnt want to put that much of an angle to my input on hydro)

Have been on travel the last few weeks, still planning to report back on the debuild of hydro from @catfan and @toddz69 on assessment of side load and seal life topic.

 

[jamesroney]

I’ve been thinking about this one a bit, I actually don’t think offset linkage creates a side force and is why they build it with the offset (specifically to avoid the side force on the hydro)

I’ve drawn it a few times to noodle on it and end up at the same conclusion.

Am I missing something in my crappy drawing?

@ksagis Yes, you are missing something.

Your "crappy drawing" is missing the bending moment component. The offset linkage creates exactly the same side force at the HB input.

A correct force diagram would include a bending moment component in the push rod. Which means that the push rod is not just pushing. It's pushing and loading sideways thru bending. (very much like an offset tie rod end.)

The HB input sees exactly the same side load in each scenario. Ironically, if I were making a Free Body diagram of the force load of the offset linkage at the HB input...I would use the axially loaded diagram.

The ONLY reason to use an offset linkage is to allow for moving the HB up or down relative to the fender/hood. You will find that offset HB inputs are drop in replacements for offset input vacuum boosters with large diameter diaphragms. When engineered without the vacuum booster constraint...the input rod is straight.

I would post a sketch, but I let my contributor status expire. Send an e-mail to jamesroney@yahoo.com, and I can send you a sketch.

But the sideways force component in either scenario is the sine of the angle times the axial force. For small angles, the axial force approximates the horizontal force. (which is the pedal effort times pedal ratio)

You can convince yourself of this by exaggerating your drawing. Just keep going to 45 degrees, and then past 60 degrees up to 90 degrees. Eventually, 100% of the force ends up as side load.

Gotta run...

 

[ksagis]

@ksagis Yes, you are missing something.

Your "crappy drawing" is missing the bending moment component. The offset linkage creates exactly the same side force at the HB input.

A correct force diagram would include a bending moment component in the push rod. Which means that the push rod is not just pushing. It's pushing and loading sideways thru bending. (very much like an offset tie rod end.)

The HB input sees exactly the same side load in each scenario. Ironically, if I were making a Free Body diagram of the force load of the offset linkage at the HB input...I would use the axially loaded diagram.

The ONLY reason to use an offset linkage is to allow for moving the HB up or down relative to the fender/hood. You will find that offset HB inputs are drop in replacements for offset input vacuum boosters with large diameter diaphragms. When engineered without the vacuum booster constraint...the input rod is straight.

I would post a sketch, but I let my contributor status expire. Send an e-mail to jamesroney@yahoo.com, and I can send you a sketch.

But the sideways force component in either scenario is the sine of the angle times the axial force. For small angles, the axial force approximates the horizontal force. (which is the pedal effort times pedal ratio)

You can convince yourself of this by exaggerating your drawing. Just keep going to 45 degrees, and then past 60 degrees up to 90 degrees. Eventually, 100% of the force ends up as side load.

Gotta run...

Yup, agreed.

 

[Oldtimer]

Actual dimensions from stock 77 vacuum booster bracket,
Brake pedal bellcrank is 1.155
Vacuum booster bellcrank is 1.827
Bracket ratio is 1 to 1.58

 

[toddz69]

Actual dimensions from stock 77 vacuum booster bracket,
Brake pedal bellcrank is 1.155
Vacuum booster bellcrank is 1.827
Bracket ratio is 1 to 1.58

View attachment 931266

Thank you!! That's incredibly helpful information. I've often wondered what the exact measurements were.

Todd Z.

 

[ksagis]

Actual dimensions from stock 77 vacuum booster bracket,
Brake pedal bellcrank is 1.155
Vacuum booster bellcrank is 1.827
Bracket ratio is 1 to 1.58

View attachment 931266

Doubling up @toddz69 thank you!

And also wondering if the pushrods were at 90 degrees. If not, there might be some changes to ratio.

Do you happen to have picture of it installed by chance with pushrods?