Rubber brake diaphragm (Has anyone knowledge about making a replacement diaphragm?)

[1wonton]

The vacuum brake diaphragm on my old vacuum brake booster is shot and can't find a replacement.  Has anyone knowledge about making a replacement diaphragm?  The original is a shaped "hat" shape but wondering if I could make a flat disc out of neoprene sheet.

[joe_padavano]

It would help to know year, model, etc. I've used these folks before.

 

https://harmonclassicbrakes.com/

[46 woodie]

Joe, I hope 1wonton takes your advice, I just checked out Harmon's website and I am going to use them in the future, Thanks.

[1wonton]

Thank you. I'll give them a call but in case they can't help me I was wondering if anyone has tried making their own diaphragm.

[ramair]

4 hours ago, 1wonton said:

Thank you. I'll give them a call but in case they can't help me I was wondering if anyone has tried making their own diaphragm.

I would think twice before undertaking that project , but if you do, let us know which state you will be driving the car with your “rebuilt” booster as some of us might stay out of harms way. Joking aside, there are at least 3 companies that I know of that have decades of experience rebuilding the different types of boosters, some are really difficult to cut apart and even harder to put together so they don’t look like you used a sledge hammer and chisel .  Most can also refinish to show standards, some are just black paint, others gold anodized type finish and others look like a cadmium or zinc?

[John348]

I am sure Harmon's is a fine rebuilder, I have used both of these vendors in the past:

 

Booster Dewey in Oregon

 

Booster Dewey

 

and Karps in Chino California, they also did silver cad plating which I needed for both the booster and master cylinder cap.

 

Karps Power Brake Service and Sleeving

[joe_padavano]

52 minutes ago, John348 said:

I am sure Harmon's is a fine rebuilder,

I use Harmon for a source of parts when I rebuild my own. We still don't know the year and model of the OP's booster, but note that all the diaphrams shown on Harmon's site are molded, not cut from flat sheet. There's a reason for this.

 

[1wonton]

I called Harmon and spoke to a (not very helpful) lady, and the first thing she asked me is "What year, make and model".  I sure miss the old days when you could go into a parts store and talk to someone who could do more than ask you what year, make and model.  Looks like everything they service are sealed units.  I couldn't find any listing for just the diaphragm itself.  This is an after-market add-on vacuum brake booster, not specific to any particular model vehicle.  It's not complicated, I don't need a "rebuilder".  Just take the small bolts out around the perimeter, replace the diaphragm and bolt it back together.  I just need an 11" rubber diaphragm.

[John348]

Speaking of make and model, why not share that information with us? We still don't know exactly what you need. 

[joe_padavano]

16 minutes ago, John348 said:

Speaking of make and model, why not share that information with us? We still don't know exactly what you need. 

Because he has an aftermarket, likely Chinesium brake booster and he is either ashamed to admit it or knows he'll draw the wrath of the originality police. Frankly, those boosters are less expensive new than the time and effort put into this so far. The OP can have fun in his quest. I've tired of the twenty questions thing. The mind reading still isn't working.

[1wonton]

Thanks for all the fun comments.  The vacuum brake pods are on a 1922 Mack truck.  These were applied after the truck left the factory (Mack did not install booster brake mechanisms).  It was no secret, just something that would mean nothing to a parts supplier or any of you highly qualified experts.  No Chinese parts, just good old American equipment of a hundred years ago.  Now that everybody commenting knows what I'm discussing I know the correct answer to my question will be instantly forwarded.

[Rusty_OToole]

5 hours ago, 1wonton said:

Thanks for all the fun comments.  The vacuum brake pods are on a 1922 Mack truck.  These were applied after the truck left the factory (Mack did not install booster brake mechanisms).  It was no secret, just something that would mean nothing to a parts supplier or any of you highly qualified experts.  No Chinese parts, just good old American equipment of a hundred years ago.  Now that everybody commenting knows what I'm discussing I know the correct answer to my question will be instantly forwarded.

We still don't know the model, make, and year of the booster. Photos may help.

[Frank DuVal]

Right. This was probably NOT a one off produced booster, but sourced from another vehicle, even if aftermarket, so it could be similar to another vehicle's booster a forum member may have seen. More information is always better than less information when trying to get answers for obscure questions. 😉

[bryankazmer]

If you try to make your own, there are a bunch of other questions

 

what was the original made of?  You want to base it on neoprene, is that usual for this service?

 

assuming neoprene is a good choice, it’s not neat neoprene, it’s a compound

what other additives and fillers, at what levels?  What durometer - this is certainly important. The old degraded one is stiffer than the replacement needs to be

[ABear]

19 hours ago, 1wonton said:

Thanks for all the fun comments.  The vacuum brake pods are on a 1922 Mack truck.  These were applied after the truck left the factory (Mack did not install booster brake mechanisms).  It was no secret, just something that would mean nothing to a parts supplier or any of you highly qualified experts.  No Chinese parts, just good old American equipment of a hundred years ago.  Now that everybody commenting knows what I'm discussing I know the correct answer to my question will be instantly forwarded.

Actually, revealing that it was something added "after the fact" is very helpful.

 

The drawing you posted is very helpful as you have 1810 Roadmaster on that drawing. I am assuming that was found on the booster, right?

 

It is entirely possible that the booster you have was a aftermarket replacement, perhaps Buick Roadmaster?

 

The problem is you don't know if it was put on in 1923 or many, many yrs after it left the factory..

 

That is where an actual picture of what you have may help someone identify it.

 

Barring that, if nothing else, you could see if there is other aftermarket booster available that might fit up to your braking system.

[Rusty_OToole]

The one time I needed a brake booster rebuilt (an  under the floor booster for a 52 Chrysler New Yorker)  I sent it to a rebuilder thru the local auto parts store. It is possible a rebuilder could match up the diaphragm from the many they keep in stock IF they had to booster and the old part to compare. But expecting some random guy on the net, to know off hand what kind of booster Mack used in 1922, and what new parts will fit it, seems like a stretch.

[1wonton]

Here are a few pictures of the brake pod.  I called Harmon but they said they don't have anything like this.  The can says, " part no. 2192548" and the diaphragm "1810 Roadmaster".  I see a company named Roadmaster still in business, but no one answered the phone.  Surely there's a suitable diaphragm out there somewhere with an 11" diameter.

[TerryB]

You might want to post your questions here —Antique Truck Club of America.  The are big fans of old Mack trucks.

https://www.antiquetruckclub.org/

 

[Rusty_OToole]

Now we are getting someplace. The lettering on the unit looks considerably newer than 1922. So you may stand a chance. It looks like the kind of vacuum booster used on big trucks vacuum brakes much bigger than a car booster.

[ABear]

After seeing that diaphragm pix, I highly doubt that a flat piece of any rubber is going to work.

 

It will have to be a molded piece or rubber with correct thickness and compliance, not typically something that can easily be replicated in a back yard. Not sure experimenting on brakes is a good idea.

 

The can does curiously look pretty much like a semi truck brake can, but modern semi brake cans are designed for pressure not vacuum so would have much heavy and thicker diaphragm and internal spring.

[dalef62]

That looks like PAT. NO., not Part No. on the can.

 

[TerryB]

Found this on a website for old Mack trucks.  It’s now part of White Post Restoration 

http://brakeboosterrebuild.com/about/

[1wonton]

Thanks Terry; I called White Post and they said they do not sell parts, only restorations.

[1wonton]

34 minutes ago, ABear said:

After seeing that diaphragm pix, I highly doubt that a flat piece of any rubber is going to work.

 

It will have to be a molded piece or rubber with correct thickness and compliance, not typically something that can easily be replicated in a back yard. Not sure experimenting on brakes is a good idea.

 

The can does curiously look pretty much like a semi truck brake can, but modern semi brake cans are designed for pressure not vacuum so would have much heavy and thicker diaphragm and internal spring.

All I need is the diaphragm, I don't need the spring or anything else.  Vacuum is quite powerful, and I think it will pull the heavy rubber.  Top speed on this truck is 18 mph, so I have no concern about "experimenting".

[ABear]

Yeah, patent number..

 

Here is link to patent which was file for in 1937, issued 1940

 

https://patentimages.storage.googleapis.com/24/85/4a/1eef33545f2334/US2192548.pdf

 

Description

 

March 5 1940. Ry R, GUNDERSQN 2,192,548

l FLUID PRESSURE POWER ACTUATOR F'iled Dec. 3. 1957 INVNTOR.` yNG/ensofpy ma/W I v l ATTORNEY.

Patented Mar. 5, 1940 UNITED 'STATES PATENT .OFFICE LUID APRESSURE l POWER ACTUATOR Ralph R. Gunderson, Los Angeles, Calif., as-

signor to- Vacuum Power Brake Company, Los' Angeles, Calif., a corporation of California Application December 3, 1937, Serial No. 177,880

 

For full description you can view here..

 

https://patents.google.com/patent/US2192548A/en?oq=us2192548

 

 

 

[ABear]

4 minutes ago, 1wonton said:

All I need is the diaphragm, I don't need the spring or anything else.  Vacuum is quite powerful, and I think it will pull the heavy rubber.

Understood, however, a flat sheet of rubber isn't going to have much deflection/capacity.. You need that molded "hat" which gives the diaphragm more travel than just a flat piece of rubber. Not to mention the molding process may have created a thicker and more ridged "top" that won't distort like a plain flat piece of rubber will. Movement was most likely more in the sidewalls of the hat.

 

If you really want to experiment, then try a piece of heavy inner tube of similar thickness, think like a old semi truck inner tube..

[46 woodie]

I have always had good luck with Master Power Brakes, www.mpbrakes.com. They have several boosters in their catalog. Do you have any idea what your insurance company would do if you made your own diaphragm?

[1wonton]

1 hour ago, ABear said:

Understood, however, a flat sheet of rubber isn't going to have much deflection/capacity.. You need that molded "hat" which gives the diaphragm more travel than just a flat piece of rubber. Not to mention the molding process may have created a thicker and more ridged "top" that won't distort like a plain flat piece of rubber will. Movement was most likely more in the sidewalls of the hat.

 

If you really want to experiment, then try a piece of heavy inner tube of similar thickness, think like a old semi truck inner tube..

Yes, I thought of that.  I've read where someone in the past has used heavy inner tube rubber with good success.  Problem is the outside diameter is 11", and the circle would have to be somewhat larger to accommodate the diaphragm in the retracted position.

[1wonton]

1 hour ago, ABear said:

Yeah, patent number..

 

Here is link to patent which was file for in 1937, issued 1940

 

https://patentimages.storage.googleapis.com/24/85/4a/1eef33545f2334/US2192548.pdf

 

Description

 

March 5 1940. Ry R, GUNDERSQN 2,192,548

l FLUID PRESSURE POWER ACTUATOR F'iled Dec. 3. 1957 INVNTOR.` yNG/ensofpy ma/W I v l ATTORNEY.

Patented Mar. 5, 1940 UNITED 'STATES PATENT .OFFICE LUID APRESSURE l POWER ACTUATOR Ralph R. Gunderson, Los Angeles, Calif., as-

signor to- Vacuum Power Brake Company, Los' Angeles, Calif., a corporation of California Application December 3, 1937, Serial No. 177,880

 

For full description you can view here..

 

https://patents.google.com/patent/US2192548A/en?oq=us2192548

 

 

 

Thanks Bear, very interesting research.  This gives an idea of about how old the booster is.  Obviously not factory.  I could go back to the original manual brake system but kind of like the way the brakes are set up now.  The truck was owned by the Riverside Water company until 1961 so maybe they added this improvement in the forties.

[1wonton]

4 minutes ago, 46 woodie said:

I have always had good luck with Master Power Brakes, www.mpbrakes.com. They have several boosters in their catalog. Do you have any idea what your insurance company would do if you made your own diaphragm?

Thanks Woodie, I'm not worried about it, I wasn't going to carry insurance anyway.

[ABear]

2 minutes ago, 1wonton said:

Thanks Bear, very interesting research.  This gives an idea of about how old the booster is.  Obviously not factory.  I could go back to the original manual brake system but kind of like the way the brakes are set up now.  The truck was owned by the Riverside Water company until 1961 so maybe they added this improvement in the forties.

google patents is pretty cool, to use you need to ad US in front of the patent number to find old patents issued in the US. Otherwise the search assumes you are looking for worldwide patents.

[ABear]

8 minutes ago, 1wonton said:

Yes, I thought of that.  I've read where someone in the past has used heavy inner tube rubber with good success.  Problem is the outside diameter is 11", and the circle would have to be somewhat larger to accommodate the diaphragm in the retracted position.

If you find a big enough inner tube for large tires you can cut open and sort of "flatten out", it will still have some "belly" in it (IE won't lay 100% flat), that is due to the fact that it was molded round.

 

Might work, just unsure if you will get as much boost as it should have and not sure how even it will be so it might not be able to keep the rod centered as the diaphragm moves.

 

As it looks right now, you have no choice but to try the inner tube since what you have is pretty much as dead as you can get.

 

Alternately, since your dealing with vacuum and not high pressure the alternate way would be to cut and glue.. Basically cut a top and side parts and glue the parts together with self vulcanizing glue. Of course each step requires overlapping joints so figuring out how to make overlaps without adding too much stiffness will be key.

 

Something else to consider, there are different types of liquid rubber products available designed for molding, with those it might be possible to make molds and vacuum form your own. Just not sure if there is any real predicable way to make a diaphragm that will be flexible enough and yet be stiff enough for your application.

 

Here is one place called Smooth-On I have a bookmark for that sells materials for mold making.

http://www.smooth-on.com/

[1wonton]

10/4 Bear.  Good idea about cutting and gluing, never thought of that, certainly worth a try, might just work.  The system has a manual override in case vacuum fails, so I would always have brakes.

[gungeey]

Cliff notes: No insurance in a Mack truck with cobbled together brakes.

Stay tuned. 

 

[Steve S. in PA]

1wonton, your brake booster looks very much like many common air chambers used on heavy trucks for everything from brake applications to tailgate releases on dump trucks.  I am sure that you can find a complete replacement if not a diaphragm, but those are available also. I don't know what the difference would be between vacuum and air, but I am sure there must be something in the big truck world that could help you out. Google air brake chamber and take a look. 

[ABear]

57 minutes ago, Steve S. in PA said:

1wonton, your brake booster looks very much like many common air chambers used on heavy trucks for everything from brake applications to tailgate releases on dump trucks.  I am sure that you can find a complete replacement if not a diaphragm, but those are available also. I don't know what the difference would be between vacuum and air, but I am sure there must be something in the big truck world that could help you out. Google air brake chamber and take a look. 

That was the first thing that came to mind when the photo was posted.

 

However, I suspect a brake chamber will have too heavy of diaphragm not to mention way to heavy of a spring. That is due to the fact that air brake chambers are designed for high air pressure, not vacuum. The brake  chamber needs considerable air pressure to over come the spring tension. No pressure and the spring holds the axle brakes in a locked mode.. Sort of a fail safe self setting emergency brake type of arraignment in case the truck or trailer were to lose air pressure.

 

Not sure if a air can without major reworking or if it would work at all..

 

I suspect, that there may be some after market vacuum boosters used by street rodders (not sure is OK to mention that here) might be a possibility to use with some retrofitting work..

[ramair]

14 hours ago, 1wonton said:

10/4 Bear.  Good idea about cutting and gluing, never thought of that, certainly worth a try, might just work.  The system has a manual override in case vacuum fails, so I would always have brakes.

Do not glue, if so you are adding another variable for disaster.  If you are just looking for a larger piece of inner tube , go to a tire shop in farm country, some of my tractor tubes are not only thicker than truck tubes, they are also huge, some of my tires are 25” wide and 6’ tall.

it is true that some of the newer tractor tires are tubeless, but all of our tractors have tubes.  I will add again my caution. I understand the truck  only goes 18 mph and you aren’t going to insure it or perhaps even drive it on a public road.  I would worry that if the brake system will stop the truck easily with vacuum pressure and you need to stop quickly for something like a grandchild and the vacuum failed, the extra force required may not stop the truck in time, 

[ABear]

1 hour ago, ramair said:

Do not glue, if so you are adding another variable for disaster.

I would tend to agree.

 

However, properly done with proper equipment it is entirely possible to "splice" rubber in a very strong manor which will most likely outlive the rest of the life of the vehicle.

 

The pictures below are tires and inner tube that was on a car I got from my Dad. In the 1950s he helped my Grand Dad change the tires on that car.. Couldn't find any tires at that time that would come close to fitting the rim. So, as the story goes, they bought 5 Model T clincher tires plus tubes and had a tire shop SPLICE in about 7" using the 5th tire and tube as splice material. The tire shop used a vulcanizing process to essentially make the spice. Those tires were still on the car when my Dad gave me the car around 2011, I replaced the tires because two of them were no longer holding air and I was not sure if the splices would survive removal and re installation.. Amazingly enough the tires actually stayed intact at the splices, but with the age I wouldn't trust them as they depend on high pressure tires (60 PSI) to keep clincher bead engaged in the rim.

 

OP IS working with vacuum, not high pressure so good self vulcanizing glue with proper overlaps most likely could work.. The downside however is where there is overlaps you lose movement which may be needed for the application..

 

Personally, I wouldn't do that, but OP was asking about possible solutions and given proper tools to do that, it is is possible to splice.. I would go with one piece of sheet rubber from an inner tube personally, slice it down the center where it would touch the rim and open and flatten out as best as possible. Might need some reinforcement (like a inner tube patch) where the spring and rod contact the rubber for added strength and wear resistance.

 

 

[Frank DuVal]

That tire and tube is AMAZING! ❗

 

I take it this Mack is mechanical brakes with an adapted booster to help move the brake linkage. Is this right? ❓

[1wonton]

21 hours ago, Steve S. in PA said:

1wonton, your brake booster looks very much like many common air chambers used on heavy trucks for everything from brake applications to tailgate releases on dump trucks.  I am sure that you can find a complete replacement if not a diaphragm, but those are available also. I don't know what the difference would be between vacuum and air, but I am sure there must be something in the big truck world that could help you out. Google air brake chamber and take a look.