Any way to Replicate Hydroboost with Mechanical Advantage?

[CharlieSheen]

My project truck will be a '53 on a 3500 chassis and drive train.I would like to free up the engine compartment by possibly mounting the booster and master underfloor.I'm not entirely comfortable with the idea,because this will be a Northeast daily-driven work truck (lots of weather and salted roads).I'll be running late model Chevy 3500 disc brakes all four corners and dually rear.

I am also not real crazy about having the pedal and linkage going down through the floor,like some aftermarket setups.I would however consider a down rod through the floor,that doesn't travel in an arc,that makes it easy to boot/grommet and seal.I also have no problem coming through the firewall with a fabricated rod and bellcrank,etc.

When I saw this setup by KIM57

It got me thinking that possibly I could fab a mechanical advantage type system with levers and bellcranks.I wouldn't have a problem mounting a master to the frame with a remote reservoir mounted in the service/tool body the truck will get.Maybe with sizing the Master cylinder right,I could have reasonable pedal effort and pedal throw?

I know there is at least one member here who has seen a lot of school bus and medium truck setups.

Could I mount the hydroboost underfloor?Yes,I guess.But now I would have to contend with exhaust and other equipment clearances.And I just don't have all the room that a bus or medium truck has available.

[_Ogre]

truk has an underfloor hydroboost w/ remote reservoir. lots of pics in my build thread.
the hydroboost gives excellent braking power, more than you'll find on the smaller diameter underfloor boosters

all vehicles had under floor brakes and linkage at one time, not sure what your concern is on that
unless you went with a rack and pinion brake pedal any brake linkage will arc, you'll need a pivot somewhere
firewall mounted pedals arc and have a pivot, no need to reinvent the wheel, just adapt to what you need

levers and bell cranks? keep it simple, the system kim built uses basically stock linkage
he only lengthened the rod to get some clearance
his pedal and lever is one piece, connected to a straight rod that goes into the mc, same as stock linkage

a simple setup would use the stock pedal and mc, cut the back of the mc off to extend the rod through the stock mc to the new mc

[CharlieSheen]

I've seen your system also Ogre,a very fine job,looks great too.

My braking situation is in a different class,though. 12,000lb truck pulling 10,000lb trailer.

Nothing magical about hydroboost,I have had a dozen of them.It just multiplies pedal force.If everything is located under hood,it is a no-brainer.Putting it way back on the frame rail,now that opens up some questions,like serviceability,weathering,hydraulic lines,etc.

I put Kim's photo in there,because his system is just SO far back,that I like the master cylinder location.Remote fill for the master could be easily located within my service body,and the Length of that linkage would give a lot of opportunity for mechanical advantage devices.Properly fabbed, a linkage would require nothing but grease gun servicing and be very tight to the chassis.

I'm wondering if there is a spec on how much of force multiplier the hydroboost unit is?With that I guess I could work backward from there.

[tmoble]

no free lunch here either. anything you do to increase the leverage will also reduce the stroke at the M/C. a little of that you can compensate with a larger diameter M/C, but there goes your leverage again.

[torchlight]

If frame mounting under the cab is an issue, consider you can also mount the master cylinder outside the frame using a through-the-frame linkage:

[wolffcub]

If you want to keep it all interior im sure you can always get creative and try to make this fit.

https://www.performanceonline.com/UN...ES-UNDER-DASH/

[CharlieSheen]

Originally Posted by tmoble

no free lunch here either. anything you do to increase the leverage will also reduce the stroke at the M/C. a little of that you can compensate with a larger diameter M/C, but there goes your leverage again.

Yes,I am pretty much agreeing with this now.I was thinking that a vacuum booster or hydraulic booster was a great idea in the engine compartment because of the convenience of having a source a few inches away anyway,therefore making a creative source of mechanical advantage bulky and unnecessary,but unless you are willing to have a foot of pedal throw,I can't really see how to make enough force to the master to operate the brakes in an HD truck.

Torchlight,I am liking your booster/master/linkage mastery.

I would be running hydroboost,vacuum boost wouldn't be enough for my purposes.

Kim57's master placement is also something I could see working for my purposes,inside or outside of frame rail.I would consider a bellcrank in there to try to have most of that linkage in a "pull" configuration.

[yossarian19]

I'm running a LS derived 4.8, 4L60E, dual exhaust & hydroboost brakes inside the stock frame rails.
It's pretty easy, really, to get a couple seals-it two piece grommets & clock them 90 degrees to each other, install that way & call it "sealed enough".
Or do like Kim57 did and use the stock pedal / linkage but fab the Hydroboost & MC into place under the truck.
Or go with a firewall setup...
In any case, the short answer is "no" - you cannot replicate the line pressures of a hydroboost unit in any reasonable fashion. Maybe with a whole lot of leverage on the brake pedal + a smaller than stock MC (engaging brakes with a lot of pedal motion) but even then I doubt it.

[1project2many]

Medium duty trucks have to follow the same rules as small trucks as far a physics are concerned. Without power brakes the system is sized to balance pedal travel, fluid capacity, and force. Smaller diameter master or larger wheel cylinders/calipers multiply force but the master has to act on a larger volume of fluid and you need to be more attentive to signs of wear. For many, many years the Hydrovac was booster of choice on medium duty trucks. It's often mounted on the frame rail rearward of the cab although starting in '55 it was in the engine compartment. The system works well enough if maintained properly and since the booster is a separate unit it can be mounted almost anywhere. The downside is that most of those were single channel and aren't going to work as well with a disc/drum combination.

There's a reason OE's like to mount the master on the firewall. It's much simpler. A cab and frame move relative to each other. You have to account for that when a brake pedal passes through a floorboard. But if the master moves with the cab all you need to do is provide a means for the brake lines to flex. Two or three coils in the line from master to frame will allow this easily. What I don't like with our trucks is the lack of panel reinforcement when most people do the firewall conversion. Maybe it's because I'm used to seeing what happens to vehicles run vehicles past 350k miles and I can imagine stress cracks forming. I'd put a support on the inside of the firewall to spread the force and flexing of countless brake applications across a larger area.

As far as under cab linkage/booster, it won't take too much imo to make the system reliable even in salt country. Greasable pivot points, shielding, and low corrosion materials will go a long way toward keeping the system from degrading to the point of failure. Unless you wash the truck fairly regularly or apply a good, oil based undercoating you're going to have rust problems elsewhere in the brake system anyway. The brake lines, unless they're made of corrosion resistant material, will usually fail from rust before any booster. 97+ G vans have ABS units in about the same area as the master on our old trucks and they don't see salt / corrosion related issues until 200k usually. The brake lines, OTOH, rust out fairly quickly.

Moving the booster outboard of the frame isn't a bad idea. Use linkage to move the pushrod outside the rails before it exits the cab. A hanging brake pedal assembly will allow the pushrod to exit at the firewall giving plenty of room for linkage to cross toward the driver's side. If using an auto trans, run the pushrod down in the area of the old clutch linkage.

Also consider that the vacuum booster in most systems could be run divorced of the master cylinder. The booster is a control valve / booster assembly with the valve actuated by the pedal and the master pushrod actuated by the booster. There is nothing that forces the booster to be bolted to the master or the firewall From an operational standpoint you could put a mile of linkage between pedal and booster and another mile between booster and master, provided you have the same amount of travel on the input and master sides of the booster with no play in the linkage. The only other caveat is that the linkage must be stout enough to allow one to apply the brakes manually if the vacuum booster fails. So you could really screw some people up by installing the booster on the firewall then running external linkage down to the master under the cab. The roadside DOT guy would love that one.

I do not know why people disregard the electric booster systems. I worked on GM cars when they were installed on new turbo Buicks and some models of FWD Pontiacs and Olds in the late '80s and '90s. They were fairly reliable and only occupied a little more area than HB. I've used Electroboost in a truck with 38" tires and a cam that wouldn't idle below 1200 rpm and the results were remarkable. There are also electric boosters used on many buses and trucks throughout the country with a fair degree of reliability so it's a proven system.

Have you begun selecting specific component parts yet? Do you know what chassis you're using? Are you keeping the stock brakes at the wheels or adapting something from other vehicles?

[CharlieSheen]

1Proj,that post belongs in the Hall of Fame,after reading your previous Hydroboost thread,I knew you were the one to ask.It is greatly appreciated.

You bring up some great points,many of which I had not considered at all,one being the consideration of having a frame-based linkage connected to an independently mounted cab.I can see now that any linkage geometry would have to consider this.

The idea of a divorced vacuum booster is also a great idea.That just frees up many possibilities.Great info,too, about electroboost.

Glad to hear your perspective about salt,rust and longevity.I haven't been around a ton of buses,and I know by law they follow a mandated,audited,maintenance schedule,but there is not one I have seen that I would be too excited about working on.The ones I have been around have been Dirty,and caked,especially on the undersides,not much priority for saving the service guy some heartache by giving the underside a good wash-down now and then.So,if anything has a Real-World perspective,it is a bus.

After seeing the system posted above by TORCHLIGHT,I also began to think about the idea of having the brake linkage exit to the outside of the frame rail before it would have to go through the frame,whether that be forward of the firewall or whether it is done through the cab itself through the floorboard near the kick panel,with a school-bus style pedal and underfloor down-rod.

I have to install or fabricate new pedals anyhow,as they were torched out of my '53 before I owned it.

My plan is to install the '53 Cab on a 2006 chevy6.0L 3500 DRW chassis and drive train.It is a running truck with Hydroboost.I probably have another 2 or 3 trucks I could poach hydroboost from,but the 2006 has a master with a remote reservoir style,which is what I will be using.

I'm a bit partial toward the hydroboost system.It is just so completely reliable.Set it,put a cooler on it,and forget it for about 150K miles.

[CharlieSheen]

I'll bring this up before maybe someone else does.I have some definite opinions based on other experience on this setup. I really can't believe anything was ever equipped with a system like this,seems like a pure hot-rodding solution.

[_Ogre]

that looks expensive too
gm diesel trucks have hydroboost set ups that will work for towing
get one out of a junkyard and start fabricating
iicr my hydroboost setup cost me $125 plus a little fabricating

[mr48chev]

What's wrong with the hydroboost that came on the truck? At least I believe 1 ton and up came with hydroboost. Why reinvent the wheel just for the sake of reinventing the wheel?

Ogre's suggestion of getting one off a diesel of the same year works well too.

I'm a bit apprehensive about using "trick" aftermarket parts in critical areas where if said part failed on the road you would be stuck until you could source a replacement which usually takes a red label box riding on a brown truck. Factory part such as a master cylinder and some parts house within a reasonable distance should have one that will work.

[CharlieSheen]

Originally Posted by mr48chev

What's wrong with the hydroboost that came on the truck? At least I believe 1 ton and up came with hydroboost. Why reinvent the wheel just for the sake of reinventing the wheel?

Yes,the existing Hydroboost is the most likely way to go.This is not to be a show truck.However I would like to keep the hydroboost and master from taking over the engine compartment and relocate them to a better spot,where they are protected,accessible and serviceable. I think from the input from 1Project2many,I have some good ideas of locations from real world conditions found in busses and medium duty trucks that are proven to work long range.

I had not considered an outside the frame rail location before,I don't know why.But seeing the truck by TORCHLIGHT,shows that this is a great location.Accessible,protected enough,away from exhaust heat and equipment.

The photo above of custom hydroboost setup is one I would NOT consider for couple of reasons,mostly for safety.That setup uses a clutch master and clutch slave cylinder to press against the booster and master.I can tell you,in my past experiences,when a clutch master or slave cylinder goes bad,it happens instantly,with no warning.You have a pedal one second,one second later you don't.No warning.If that happens with brakes,you are completely out of luck.Also,lets say you lose a power steering belt and loose hydroboost.Can you rely on a clutch slave cylinder to hold up to the huge force needed to stop the truck manually?I'd rather take my chances with a hefty steel linkage and stand on the pedal with both feet if you have to.

[tmoble]

here's a linkage ratio solution:

http://camburg.com/store/wp-content/...rakePed_05.jpg

same place those pics of remote master system a few posts above came from. Might be trouble finding enough room for that long swing pedal.

[CharlieSheen]

And Then Reality Set In. Looking at some web photos of old trucks and their clutch linkages and pedals transported me back in the day to sloppy z-bars,sloppy linkages and broken return springs and pedals that just never returned quite all the way to the top.Uggh.

[steve aleve]

So I am mounting 54 3100 with a frame mount hydroboost on an s10 frame and I will have to fab custom pedals and linkage. Similar to what torchlight posted up the page a bit. Does Anyone know where to get these types of components? Like the shaft through the frame, sleeves and brackets? It turns out I don't really even know what this stuff is called to do a search on it lol. Thanks in advance

[yossarian19]

Some of the words you might be looking for are yoke, heim joint, rod end, bushing, pillow block bearing... go to your local (big) hardware store and start looking at all the oddball stuff they carry. You can get a lot done with some tools & a good local hardware store.
I wouldn't really recommend going frame mounted myself. I guess I can see why it works for a lot of folks, as you shouldn't really need to be messing with your master cylinder very often. Me? I am constantly messing with my truck, changing this or that, and since I built it out of junkyard parts I also get to repair it when things wear out. Service friendly is a big deal.

[steve aleve]

Thanks yossarian19!!! that is exactly what i needed!! I would have never thought to look up pillow block bearings which also lead to flanged bearing housings!!!