26 Brake Cam Question

Discuss all things Model T related.
Forum rules
If you need help logging in, or have question about how something works, use the Support forum located here Support Forum
Complete set of Forum Rules Forum Rules

Topic author
Scott C.
Posts: 495
Joined: Sun Jan 06, 2019 11:44 am
First Name: Scott
Last Name: Clements
Location: Waynetown Indiana
MTFCA Number: 49592

26 Brake Cam Question

Post by Scott C. » Sun Nov 17, 2019 1:35 am

Does any one sell one piece brake cams for a 26? I just bought a set from Lang's and the cam lobes are separate parts pinned onto the shaft.


Topic author
Scott C.
Posts: 495
Joined: Sun Jan 06, 2019 11:44 am
First Name: Scott
Last Name: Clements
Location: Waynetown Indiana
MTFCA Number: 49592

Re: 26 Brake Cam Question

Post by Scott C. » Sun Nov 17, 2019 4:45 pm

Here is a picture of one of them. I really don't like the way it is made. It looks like an accident waiting to happen!!
IMG_0510.jpg

User avatar

Mark Gregush
Posts: 2945
Joined: Sat Jan 05, 2019 1:57 pm
First Name: Mark
Last Name: Gregush
Location: Portland Or
Board Member Since: 1999

Re: 26 Brake Cam Question

Post by Mark Gregush » Sun Nov 17, 2019 5:35 pm

The 26/27 brakes were not meant to be service brakes, they are parking brakes. OP: I do not see any difference between the lever which is pinned to the shaft or a cam being pinned as long as they are tight on the shaft, you could shear ether one if one put enough force on them. If you don't like them might I suggest looking for good original ones.
I know the voices aren't real but damn they have some good ideas! :shock:

1925 Cut down pickup
1920 Dodge touring
1948 Ford F2 pickup


Scott_Conger
Posts: 2798
Joined: Sun Jan 06, 2019 11:18 am
First Name: Scott
Last Name: Conger
Location: Clark, WY
Board Member Since: 2005

Re: 26 Brake Cam Question

Post by Scott_Conger » Sun Nov 17, 2019 5:49 pm

I agree with Mark. I wouldn't worry about it unless there is something very obviously deficient in its assembly, and you're the only one that can conclude that, not us.
Scott Conger

Full Flow Float Valves - deliver fuel like Henry intended!


Topic author
Scott C.
Posts: 495
Joined: Sun Jan 06, 2019 11:44 am
First Name: Scott
Last Name: Clements
Location: Waynetown Indiana
MTFCA Number: 49592

Re: 26 Brake Cam Question

Post by Scott C. » Sun Nov 17, 2019 5:52 pm

I would agree other than the diameter of the shaft is larger at the lever end. The shaft appears to be only 7/16" in diameter at the cam end. Subtract the 3/16" pin diameter and your left with 1/4". Divide that by 2 and you have only 1/8" of material left on each side to hold the forces that are applied by the hand brake lever. That is what concerns me. The parking brake is also the emergency brake!


Scott_Conger
Posts: 2798
Joined: Sun Jan 06, 2019 11:18 am
First Name: Scott
Last Name: Conger
Location: Clark, WY
Board Member Since: 2005

Re: 26 Brake Cam Question

Post by Scott_Conger » Sun Nov 17, 2019 6:03 pm

Sounds like you have come to a conclusion, then.
Scott Conger

Full Flow Float Valves - deliver fuel like Henry intended!

User avatar

Mark Gregush
Posts: 2945
Joined: Sat Jan 05, 2019 1:57 pm
First Name: Mark
Last Name: Gregush
Location: Portland Or
Board Member Since: 1999

Re: 26 Brake Cam Question

Post by Mark Gregush » Sun Nov 17, 2019 6:20 pm

I agree that he has decided.
If you want to think of it as an emergency brake, fine. I have yet to even consider reaching down to grab the handle using it as such when making a panic stop. Don't matter if 21 or 30 in tires, skidding is not stopping and your transmission brake should be able to do that much. With the Model T steering you should have both hands on the wheel in an emergency more esp if rolling backwards. Now if you have it hooked up to the parking brakes, different story, well sort of.
I know the voices aren't real but damn they have some good ideas! :shock:

1925 Cut down pickup
1920 Dodge touring
1948 Ford F2 pickup

User avatar

Henry K. Lee
Posts: 3636
Joined: Sun Jan 06, 2019 11:09 am
First Name: Henry
Last Name: Lee
Location: South Pittsburg, TN
MTFCA Number: 479
MTFCA Life Member: YES

Re: 26 Brake Cam Question

Post by Henry K. Lee » Sun Nov 17, 2019 6:34 pm

I can not see how that could be safe. Meaning a smaller diameter round shaft in round hole pinned. I will give the benefit of doubt if the item has been proven in an independent lab on the shear/clevis strength test to the item it is replacing. Now pull like hell in an emergency situation and see what happens over time. As some of you comment, "In Henry's day" well, I do not believe he would have done that when it comes to public safety. When it comes to safety, only better, proven methods of material construction/techniques should be used. Saving dollars to meet the demands at an affordable price is not in the interest of any hobby. One person gets hurt, that is one too many in my opinion.

I am with Scott C.

My $.04 worth,

Hank


Allan
Posts: 1990
Joined: Sun Jan 06, 2019 7:21 pm
First Name: Allan
Last Name: Bennett
Location: Gawler, Australia

Re: 26 Brake Cam Question

Post by Allan » Sun Nov 17, 2019 6:47 pm

I wonder what keeps the pin in place? Had I the need to fit these, the shaft would be chucked in the lathe, a deep groove machined at the cam and shaft interface, and a substantial weld used to fill the groove. All the while it was fitted I'd be looking for some good original forged pieces. Assemblies such as this are akin to the two piece, pressed together spring shackles.

Allan from down under.


Billdizer,Spencer In
Posts: 170
Joined: Sun Jan 06, 2019 1:58 pm
First Name: Bill
Last Name: Dizer
Location: Spencer, In
MTFCA Number: 28610
MTFCA Life Member: YES
Board Member Since: 2014

Re: 26 Brake Cam Question

Post by Billdizer,Spencer In » Sun Nov 17, 2019 6:52 pm

I agree with Scott the design is poor. Having had a pinion bearing grenade, shuck two teeth off the pinion gear, and leave me freewheeling down a hill towards a parking lot and waterfalls in a state park, you can bet I was pulling on those parking brakes/ emergency brakes for all they were worth! They were in poor shape and didn't do much, and ultimately the driveshaft turned enough for a few teeth to catch, and we slid to a stop! Rollback wrecker ride home, rebuilt the rear end, which already had new thrusts back in the fifties, and the parking brakes will now stop it if they need to! I think if those are the only ones to be had, I would have them tig welded at both ends and cut the bushing back a bit if necessary for the weld to clear. With the larger shoes and better lining, there is more stress on those cams than the 1925 and back.


Scott_Conger
Posts: 2798
Joined: Sun Jan 06, 2019 11:18 am
First Name: Scott
Last Name: Conger
Location: Clark, WY
Board Member Since: 2005

Re: 26 Brake Cam Question

Post by Scott_Conger » Sun Nov 17, 2019 11:19 pm

I'm not responding to this to defend the design...it is what it is, and it is inferior to a one-piece or two piece welded assembly. The responses thus far running against it, however are not addressing the stress area, though, so are clearly just "gut reactions" to the design.

Well enough.

Has anyone thought it through and asked themselves about the lever that actuates it and the stresses it sees relative to the cam? And has ANYONE heard of that properly assembled lever failing? In the many years on the forum, and touring I haven't heard of a single instance. And brother, I've seen some crummy rivet jobs.

I don't pooh-pooh safety, but this is a parking brake. Drive line failures, whatever other panic use is deemed necessary, it was never more than a parking brake, and until someone shows me the stress analysis that shows that joint failing before all the other riveted joints in the system from the brake lever back I'm not losing sleep over it if it was my car. For the tortional stress it will see, if it is properly fitted (and no one other than the part's assembler knows that, I suppose) that is a robust joint.
only 1/8" of material left on each side to hold the forces that are applied by the hand brake lever
This is not true. The cam itself is adding significant hoop strength to the assembly. If on the other hand, you were looking at a roll pin there, there would be great cause for concern. Given the available "oomph" available on the handbrake, even with a safety factor, anyone that thinks they're going to shear that solid pin with the forces available, I believe are mistaken. If it only went 1/2 way through, like a set screw...UH-OH, but that's not the case here.
Scott Conger

Full Flow Float Valves - deliver fuel like Henry intended!


Dan McEachern
Posts: 482
Joined: Sun Jan 06, 2019 11:08 am
First Name: DAN
Last Name: MCEACHERN
Location: ALAMEDA,CA,USA

Re: 26 Brake Cam Question

Post by Dan McEachern » Mon Nov 18, 2019 12:08 am

Why not just make it in one piece like the original and be done with it?

User avatar

Mark Gregush
Posts: 2945
Joined: Sat Jan 05, 2019 1:57 pm
First Name: Mark
Last Name: Gregush
Location: Portland Or
Board Member Since: 1999

Re: 26 Brake Cam Question

Post by Mark Gregush » Mon Nov 18, 2019 2:07 am

The ones I have on a couple of large drum housing look to be machined forgings.
Seems to me there was talk in the past about 2 piece 26/27 cams but this is all I could find.
Read the 2ed post;
http://www.mtfca.com/discus/messages/50 ... 1428792374
Ironic I would say.
I know the voices aren't real but damn they have some good ideas! :shock:

1925 Cut down pickup
1920 Dodge touring
1948 Ford F2 pickup


Dan Hatch
Posts: 1564
Joined: Tue Jan 08, 2019 7:31 pm
First Name: Dan
Last Name: Hatch
Location: Alabama
MTFCA Number: 49974

Re: 26 Brake Cam Question

Post by Dan Hatch » Mon Nov 18, 2019 6:53 am

After you post number 2, read post number 6. That one tells the whole story.


Joe Bell
Posts: 550
Joined: Thu Feb 21, 2019 1:20 pm
First Name: Joe
Last Name: Bell
Location: Tiffin Ohio
MTFCI Number: 24066

Re: 26 Brake Cam Question

Post by Joe Bell » Mon Nov 18, 2019 8:01 am

My thought are some one took the time to make them, if you piss him off from his design there will be no more. That cam is for a Parking Brake not an emergency brake, But if you are using them for an Auxillary brake I would use a different cam. I did not make these and have nothing to do with who ever did but it reminds me of years ago when I was rebuilding my Fordor, trying to find the pot metal regulators for the windows. I had one made then seen that some one was repopping them, they where not perfect but useable some one got on the Forum and raised a big stink about them and the guy decided to not make them any more. So what I am getting, at be glad some one is making them and if you do not like them make your own and find out what some of these people go through just to keep this hobby going. Just my two cents worth!


Scott_Conger
Posts: 2798
Joined: Sun Jan 06, 2019 11:18 am
First Name: Scott
Last Name: Conger
Location: Clark, WY
Board Member Since: 2005

Re: 26 Brake Cam Question

Post by Scott_Conger » Mon Nov 18, 2019 10:08 am

Joe

right on, on each point.
Scott Conger

Full Flow Float Valves - deliver fuel like Henry intended!


Norman Kling
Posts: 1324
Joined: Tue Jan 08, 2019 1:39 pm
First Name: Norman
Last Name: Kling
Location: Alpine California

Re: 26 Brake Cam Question

Post by Norman Kling » Mon Nov 18, 2019 11:04 am

It is not good to use the rear wheel brakes for "emergency" unless you also use the low pedal. Reason is that pulling back the lever puts it into neutral if you pull it while you are in high gear. I like to put auxiliary brakes on the rear wheels which are activated by the brake pedal. Then when you push the pedal hard you are using both the aux. brake and the transmission brake. The parking brake lever also activates the aux. brake so by pulling the hand lever you are activating all three sets of brakes. This should be enough to slide the wheels and that's all the braking you get unless you install front wheel brakes.
I agree that the pin is not as strong as the solid shaft and cam. But if you have the aux. brakes installed, you should only need the lever if the transmission brake fails when you are rolling backward and if you pull the lever quickly after that occurs, you should not have a problem.
Norm


Kuhner
Posts: 40
Joined: Sun Jan 06, 2019 5:12 pm
First Name: Greg
Last Name: Kuhnash
Location: Lore City, Ohio
MTFCA Number: 28086
MTFCI Number: 21773
Board Member Since: 2006

Re: 26 Brake Cam Question

Post by Kuhner » Mon Nov 18, 2019 12:33 pm

Isn’t the lever on the other end just held by the same pin?
I think the 26 -27 had one pin, earlier 2 pins.

Greg
“I don’t like nice people. I like tough, honest people”. - Woody Hayes

User avatar

TRDxB2
Posts: 1593
Joined: Tue Jan 08, 2019 4:56 pm
First Name: Frank
Last Name: Brandi
Location: Moline IL
Board Member Since: 2018

Re: 26 Brake Cam Question

Post by TRDxB2 » Mon Nov 18, 2019 1:19 pm

The entire emergency brake system needs to put in focus to determine the weakest link. I can't see the possibility of the pin in the cam shearing given its position and on the other end a lever arm that's only 2 1/2 inches long. Yes the hand break arm is much longer "lever" but it is pulling on another 2 1/2" lever arm connected by a rod with clevis pins in yoke ends. Each lever arm and yoke end has a loop at the end of its neck. So the question is what breaks first: a loop or pin? Think about how much force you could apply to a wrench that's only 2 1/2 " long.
(Note not sure about the lever its T-864 - I just used it for the example and that is a used old designed cam)
Attachments
IMG_0404[1].JPG

User avatar

Henry K. Lee
Posts: 3636
Joined: Sun Jan 06, 2019 11:09 am
First Name: Henry
Last Name: Lee
Location: South Pittsburg, TN
MTFCA Number: 479
MTFCA Life Member: YES

Re: 26 Brake Cam Question

Post by Henry K. Lee » Mon Nov 18, 2019 2:19 pm

I think the original handbook says differently about it being a parking brake....?

IMG_2359.jpeg


Just a side note: The distance of the pulling arm (Forged Steel) 3/4" and the hand/emergency brake handle(Forged Steel) 3/4" area is not as much forces due to diameter vs fulcrum. That lower 3/16" pin at the cam has a multiplier of about 4 @ 7/16".


Interesting discussion,

Hank


Topic author
Scott C.
Posts: 495
Joined: Sun Jan 06, 2019 11:44 am
First Name: Scott
Last Name: Clements
Location: Waynetown Indiana
MTFCA Number: 49592

Re: 26 Brake Cam Question

Post by Scott C. » Tue Nov 19, 2019 12:42 pm

Wow!! Some of these responses are not what I thought that I would receive. I asked an honest question and voiced an honest concern. I did not insult anyone. Any way, here is an up date on what I have found. I had a hardness check done and the results were, the original tested at 8 and the reproduction one tested at 20. So, the new one does test significantly harder. I think that is a positive. I removed the pin and pulled the lobe. The shaft is splined, while the lobe is not. The pin is also slightly splined. So, it appears that the posted issue from the past has been addressed by the supplier. I now, do think that they are safe to use.
IMG_0521.jpg
IMG_0522.jpg
IMG_0523.jpg

User avatar

Henry K. Lee
Posts: 3636
Joined: Sun Jan 06, 2019 11:09 am
First Name: Henry
Last Name: Lee
Location: South Pittsburg, TN
MTFCA Number: 479
MTFCA Life Member: YES

Re: 26 Brake Cam Question

Post by Henry K. Lee » Tue Nov 19, 2019 12:51 pm

I will be the first to admit when I am wrong. But I did give the benefit of the doubt as stated, and the design is what stumped me. Since the majority of us have had issues with parts, ie, Hyatt Bearings, driveshafts, ring and pinion, etc, we all get a little concerned. With new folks coming in, they need to know facts from fiction. So first my apology to the person who made it if I insulted you by my concerns. Second, Thank You Scott Clements for taking one apart and investigating with time to test it.

All the Best to All,

Humbled Hank in Tin-A-See


jab35
Posts: 392
Joined: Sun Jan 06, 2019 12:28 pm
First Name: James
Last Name: Bartsch
Location: Dryden, NY 13053
MTFCA Number: 30615
MTFCA Life Member: YES

Re: 26 Brake Cam Question

Post by jab35 » Tue Nov 19, 2019 1:07 pm

And the hardness of the pin was?? That's a critical piece of this assembly.


Scott_Conger
Posts: 2798
Joined: Sun Jan 06, 2019 11:18 am
First Name: Scott
Last Name: Conger
Location: Clark, WY
Board Member Since: 2005

Re: 26 Brake Cam Question

Post by Scott_Conger » Tue Nov 19, 2019 1:53 pm

So, with no stress analysis yet, our "gut" feel is that it's fine. The information is available on the interweb, including Ultimate Strength of materials, and calculators which can have a safety factor dialed in. I'm betting I'm not the only one who checked, but I'm betting also that it isn't many, either. It may still be useable after reassembly, but can state confidently that it's integrity is now compromised from when it arrived new, sealed in a bag. So now we feel better about the design, but have a compromised part. Huh.

If there is a desire to install the strongest part, either weld this thing or throw it away. Those pinned and knurled parts were plenty strong tortionally as new, but a separated and reassembled knurl is quite compromised and now the pin is doing much more work (and it's press fit is now compromised as well).

At least we all know how the thing is assembled

And to the guy who makes these things: Thank you. I don't own a car that these fit and probably never will, but the point is that you are supplying the hobby with a part that no one else is, and I appreciate it.
Scott Conger

Full Flow Float Valves - deliver fuel like Henry intended!

Post Reply Previous topicNext topic