Hydroboost Installation question

[lars]

My brake setup is very similar- ok, scratch that- identical as far as I know- to Todd's. Can't measure anything because it's not running and won't be for a few months. But Todd's numbers sound about right. Adding to the equipment he described, we are also running 2010-ish Dodge 1500 front brakes which actually have slightly less caliper piston area than the 70's vintage big piston Ford calipers they replaced, and Explorer rear discs. Entirely qualitative but that combination has been the magic bullet combination of brake "feel" (linearity?) and stopping power, right up to the limit of traction. I wish my new Tacoma had brakes as nice as those on my Bronco.

Agreed that in the stock location (what I have) the boost unit and master cylinder occupy a lot of space out in the middle of everywhere, but that leaves more room on my driver's inner fenderwell to bolt crap down. As with horizontal surfaces everywhere, can't have too much, and even then they fill up.

 

[hunter1]

Yes, and I have long admired your fabrication skills. (from afar...) It turns out that @ba123 created a similar configuration in his build thread.
But I'm running a clutch. (and yes, I could hang a clutch pedal on your pivot shaft, but I would lose the air vent box...)

He also used a 1:1 Bellcrank ratio. By that, I mean that his pivot rod to actuator pin length is exactly the same. Which means that you don't get any multiplication in the bellcrank. If that is true, the I suspect that you will see a nominal 3 inches of pedal travel on a 1.25 bore master cyl.

If you have those pillow blocks mounted in the factory location, I imagine that you are also 1:1 on the bell crank. Can you please confirm your pedal travel in inches? I'm guessing the answer will be about 3 inches of stroke.

I'm doing similar and still using the clutch pedal. Either way you would lose the vent. I ended up using bronze flanged bushings instead of bearings and will have to wait to see how it works.

 

[ntsqd]

An outlier data point: FSB, not EB, and maybe not useful at all but here it is:
Stock pedal, stock M/C, Vanco supplied H-B unit. When the rear brakes don't get air in them (i.e. right after a bleeding) pedal travel is about an inch, maybe a little more. Once brakes are engaged the pedal has maybe another inch of travel in it where upon you would be heading thru the windshield. In spite of how it reads in print, the brakes not touchy, are super easy to modulate, and are just enough effort to make modulation easy.
According to RA it is a Ø1.125" m/c bore. I'll need to measure the pedal ratio if there is interest. Front calipers are the std GM Ø2-15/16" and the rear calipers are '00 Expedition.

Been too long since I drove the Bronc-up to remember what it's H-B brake pedal travel is like. It was the first H-B conversion that I'd ever driven and it convinced me to convert everything else in my fleet.

 

[Yeller]

My HB uses a typical GM disc brake swap with 3” diameter pistons and 11” drum brakes. Uses a 1-7/16 bore master, came with the booster. Booster is direct connected to the pedal. Total pedal travel is under 1”, barely perceptible when you step on the pedal. Feel is firm, easy to modulate, and plenty powerful. I’ve considered going to a smaller bore master to increase the travel but it stops nice. Probably not super helpful post but does help confirm that a much larger bore master still works with hydroboost that would never work otherwise.

 

[ksagis]

OK, so you are using something like the Hydra-Tech bracket bolted to firewall with the slightly angled mount?

I don't think those can ever be right, without some kind off link bar in the middle.

I think the geometry can be fine as there are multiple Bronco gurus with existence proofs of it working very nicely.

There’s a whole lot of moving parts that need to work together, MC bore size (more flow volume for same piston translation), pedal ratio, hydro power piston diameter, linkages in between, etc

 

[toddz69]

I think the geometry can be fine as there are multiple Bronco gurus with existence proofs of it working very nicely.

There’s a whole lot of moving parts that need to work together, MC bore size (more flow volume for same piston translation), pedal ratio, hydro power piston diameter, linkages in between, etc

That last sentence pretty much sums it up! Lots of little things to consider and work through, but an engineer's delight in many ways .

As to the geometry on the Hydratech bracket - I'm not sure what the angle is on it because I never have used one. My initial design was straight off the firewall and the original piece that Hydratech built was also straight. After we started working on different engines/configurations, we knew that wouldn't work so the angled bracket came into being and I'm pretty sure Paul just makes that one part now to keep SKUs to a minimum. When I was first learning the details of hydro boost in the late 90s/very early 00s, the angle of the pushrod and its effect on seals/wear in the bore was a big question for me too. I contacted Vanco and explained what I was doing and their response was an immediate "oh that will never work, you'll wear out seals in no time" or words to that effect and then essentially hung up on me. OK. Some time later I thought, "I'm going to go see what the angle is on the pushrod in my Super Duty". Took a look - sure enough, the pushrod in my pickup was at a steeper angle than the one in my Bronco. If I'm doing better than the OEM's installation, I figured I would be just fine. I get a little bit of seepage at the back of the unit but that's pretty typical for any h-boost unit. I haven't watched the angle of the pushrod as it moves through its travel in the Bronco vs. the pickup but I think they're pretty similar.

Todd Z.

 

[ntsqd]

I haven't made a documented survey of OEM H-B installs, but my observation is that systems using a H-B employ a m/c with a larger to considerably larger bore size. I attribute that to the far greater force that the hydraulics can provide over that which can be had with vacuum. This seems like it should be obvious, but my experience has proven otherwise.

 

[phred]

Great! Can you please tell me what your astrovan/corvette master cylinder is bolted to?

1. Direct to firewall with a modified pedal box.

Correct, made a 1/4” steel plate to reinforce the firewall. Bolted it to firewall and the booster is held to the plate using the big not on the unit itself

2. In line with factory pedal with a custom astrovan plate delete but using the giant nut.

That it.

3. Offset on an angle bracket using a Bronco bracket.

No offset. 1” body lift and straight oon the firewal

4. Offset on an angle bracket using a custom bracket.
5. In line with factory pedal using an offset bracket.

Directly online with the stock pedal box.
The 78 using the f250 stuff is exactly the same.

 

[toddz69]

I haven't made a documented survey of OEM H-B installs, but my observation is that systems using a H-B employ a m/c with a larger to considerably larger bore size. I attribute that to the far greater force that the hydraulics can provide over that which can be had with vacuum. This seems like it should be obvious, but my experience has proven otherwise.

I've done some surveys over the years comparing master cylinder bore diameters to total piston areas, etc., trying to look for some correlations but never really came up with anything concrete. This was done without any consideration for any other factors like pedal ratios, power piston diameters, etc. I should have paid more attention to some clues over the years but I'm often a slow learner. Back in the mid 00s, I briefly tested some 2 piston PBR calipers for a friend of mine (which have a much smaller total piston area than the calipers we use on our trucks) and realized I had a much higher and firmer pedal than I did with the stock calipers. I didn't end up using the PBRs. A few years later I did a conversion on an elderly friend's Bronco that used a stock angled bracket and I noticed a higher and firmer pedal as well (thanks to a lower effective pedal ratio than what I using). And then about 5 years ago I had an opportunity to drive a Velocity Bronco with a Hydratech setup on it (using 1.125" Wilwood master) with Wilwood brakes. The Wilwoods have smaller piston areas as well compared to the stock brake calipers so they felt really good. I finally decided to bump up from a 1.125" master to a 1.25" master and it made a big difference in pedal feel and pedal height.

I also follow the braking stuff on pro-touring cars a lot and they often recommend a 7/8-15/16" master for manual brakes (usually multi-piston calipers), 1" for vacuum, and 1.125" for h-boost on those, which makes sense when you look at the piston area totals on the brakes on those cars.

Todd Z.

 

[ksagis]

That last sentence pretty much sums it up! Lots of little things to consider and work through, but an engineer's delight in many ways .

As to the geometry on the Hydratech bracket - I'm not sure what the angle is on it because I never have used one. My initial design was straight off the firewall and the original piece that Hydratech built was also straight. After we started working on different engines/configurations, we knew that wouldn't work so the angled bracket came into being and I'm pretty sure Paul just makes that one part now to keep SKUs to a minimum. When I was first learning the details of hydro boost in the late 90s/very early 00s, the angle of the pushrod and its effect on seals/wear in the bore was a big question for me too. I contacted Vanco and explained what I was doing and their response was an immediate "oh that will never work, you'll wear out seals in no time" or words to that effect and then essentially hung up on me. OK. Some time later I thought, "I'm going to go see what the angle is on the pushrod in my Super Duty". Took a look - sure enough, the pushrod in my pickup was at a steeper angle than the one in my Bronco. If I'm doing better than the OEM's installation, I figured I would be just fine. I get a little bit of seepage at the back of the unit but that's pretty typical for any h-boost unit. I haven't watched the angle of the pushrod as it moves through its travel in the Bronco vs. the pickup but I think they're pretty similar.

Todd Z.

Oh wow, you got my attention with the detail on your SuperDuty angle. Would it be possible to get a rough idea of the angle (I would love to go lower than 5:1 but was worried about side load and seals)? Interesting on what Vanco said….

A picture would be fine if measuring the angle is a pain.

 

[toddz69]

Oh wow, you got my attention with the detail on your SuperDuty angle. Would it be possible to get a rough idea of the angle (I would love to go lower than 5:1 but was worried about side load and seals)? Interesting on what Vanco said….

A picture would be fine if measuring the angle is a pain.

I will, but it'll have to wait until I'm home from vacation......give me a week and I'll get it!

Todd Z.

 

[bmc69]

I installed the booster in my '69 EB on factory angled bracket with the factory linkage. Dual-piston front D-44 calipers and stock D60 rear drum (all from '78 F-250). F-250 MC.

I can't measure the pedal travel now (sold truck) but it was definitely less than 3". The first time I applied the brakes after the install I literally almost hurt myself...I was not prepared for the aggressive stop. Took a while to get used to barely "resting" my foot on the brake pedal instead of actually pushing on it much.

The direct-push firewall mount hboost setup on my '78 Bronc has probably 4" of pedal travel because I need to get a larger diameter MC and haven't gotten around to it yet. Despite that, it easily locks up the 40" tires on pavement, as I found out when an idiot pulled out right in front of me at an intersection. That truck is on '79 D60 front and '89 Sterling rear axles.

 

[big blue]

View attachment 927459
I'm doing similar and still using the clutch pedal. Either way you would lose the vent. I ended up using bronze flanged bushings instead of bearings and will have to wait to see how it works.

Is the tab bolted to the h-boost , I can't see the other 2 nuts so I'm assuming it is?

 

[big blue]

View attachment 927459
I'm doing similar and still using the clutch pedal. Either way you would lose the vent. I ended up using bronze flanged bushings instead of bearings and will have to wait to see how it works.

Also did you drill thru the pedal and the shaft and use a roll pin or small bolt?

 

[hunter1]

Is the tab bolted to the h-boost , I can't see the other 2 nuts so I'm assuming it is?

Not sure what you mean by "tab"? the two outside HB studs hold the outer shaft bronze bushing bracket I fabricated. Is that what you are asking?

 

[hunter1]

Also did you drill thru the pedal and the shaft and use a roll pin or small bolt?

Yes, drilled through the pedal boss and have a hardened dowel through it.

 

[hunter1]

Yes, drilled through the pedal boss and have a hardened dowel through it.

I believe the picture I posted did have a roll pin in it. This is after I installed the solid dowel. It is spotted with a weld on the other side just in case it starts to work loose, but very tight through the shaft and boss.

 

[hunter1]

I believe the picture I posted did have a roll pin in it. This is after I installed the solid dowel. It is spotted with a weld on the other side just in case it starts to work loose, but very tight through the shaft and boss.

View attachment 927564

 

[big blue]

Not sure what you mean by "tab"? the two outside HB studs hold the outer shaft bronze bushing bracket I fabricated. Is that what you are asking?

Yes that was what I meant.

 

[ba123]

Yes, and I have long admired your fabrication skills. (from afar...) It turns out that @ba123 created a similar configuration in his build thread.
But I'm running a clutch. (and yes, I could hang a clutch pedal on your pivot shaft, but I would lose the air vent box...)

He also used a 1:1 Bellcrank ratio. By that, I mean that his pivot rod to actuator pin length is exactly the same. Which means that you don't get any multiplication in the bellcrank. If that is true, the I suspect that you will see a nominal 3 inches of pedal travel on a 1.25 bore master cyl.

If you have those pillow blocks mounted in the factory location, I imagine that you are also 1:1 on the bell crank. Can you please confirm your pedal travel in inches? I'm guessing the answer will be about 3 inches of stroke.

Yes, my config was inspired by Jon for sure!

James, I can measure and take a video for you today and text. Just got back from San Diego last night.