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Disk brake to driveshaft?


CatBird
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Some early cars had the service brake on the driveshaft notably Ford Model T. One drawback was that if one back wheel slipped on ice or mud  it could spin backwards while the opposite wheel spun forwards resulting in no braking.

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On 3/8/2021 at 8:42 PM, Rusty_OToole said:

Some early cars had the service brake on the driveshaft notably Ford Model T. One drawback was that if one back wheel slipped on ice or mud  it could spin backwards while the opposite wheel spun forwards resulting in no braking.

 

Rusty, trying to understand. The Model T brake pedal tightens a band in the transmission, stopping effectively stopping the driveshaft, so that the rear drive wheel stops, not spins, and the other wheel freewheels ....... Please explain. Of course the handbrake stops each rear wheel.

So, that, a disk brake on the driveshaft can only affect the driven wheel, not the freewheeling other wheel. Only a driveshaft disk brake could only stop both rear wheels if there was a solid rear axle. When you turn a corner, the outer wheel has to turn faster than the inner wheel.

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3 hours ago, CatBird said:

 

Rusty, trying to understand. The Model T brake pedal tightens a band in the transmission, stopping effectively stopping the driveshaft, so that the rear drive wheel stops, not spins, and the other wheel freewheels ....... Please explain. Of course the handbrake stops each rear wheel.

So, that, a disk brake on the driveshaft can only affect the driven wheel, not the freewheeling other wheel. Only a driveshaft disk brake could only stop both rear wheels if there was a solid rear axle. When you turn a corner, the outer wheel has to turn faster than the inner wheel.

Be happy to explain. The brake locks the driveshaft. Both back wheels SHOULD stop, and usually do. Under unusual circumstances, when there is no traction on one wheel that wheel will spin backwards while the opposite wheel spins forwards due to the differential gears. You can demonstrate this by jacking up the back of a (rear wheel drive) car with the transmission in 'Park' and turning one wheel, the opposite wheel will turn in the opposite direction.

This only happens when one wheel is on ice or slippery mud while the other is on dry pavement. It sometimes happened in traffic, if there was ice or mud in the gutter one wheel would spin and the car would run into the car ahead with no braking effect even though the drive shaft was stopped.

Of course if you have a limited slip differential this will not happen but such devices were not made when the Model T was new.

Edited by Rusty_OToole (see edit history)
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Posted (edited)

Rusty, thanks for the explanation. It helps. My original question was when I spun the rear tire(s) on my 1957 Chevy from revving the engine and dropping the clutch, only one black mark came from my right rear wheel. This indicated to me that the left rear wheel was not being driven by the driveshaft. Following this logic was that the left rear wheel was free-wheeling. So how could the driveshaft stop both wheels. Somehow my logic is flawed? I am missing the point?


Of course this was in the days before limited slip.

I appreciate your knowledge as you have great posts that I have followed and implemented!

I was thinking about the brakes on my Pierce, which has only two brakes on the rear wheels. Maybe going disk on the driveshaft as many of my touring buddies are doing this. From your logic and my friends, additional disk braking is useful in mountainous roads. Of course gearing down certainly helps! 

Of course having the original brakes in proper adjustment is paramount! As long as the rear wheels can lock up, that is all you can have.

Edited by CatBird (see edit history)
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14 minutes ago, CatBird said:

Rusty, thanks for the explanation. It helps. My original question was when I spun the rear tire(s) on my 1957 Chevy from revving the engine and dropping the clutch, only one black mark came from my right rear wheel. This indicated to me that the left rear wheel was not being driven by the driveshaft. Following this logic was that the left rear wheel was free-wheeling. So how could the driveshaft stop both wheels. Somehow my logic is flawed? I am missing the point?

 

What you're missing is that braking relies on friction, both between the brake shoes and drums and also between the tires and the ground. The latter is the issue. Obviously, if there is low or no friction between the tires and the road surface, then it doesn't matter how many or where you have brake mechanisms, the vehicle still won't stop. The problem with a driveshaft brake is that holding any one of the three shafts connected to the differential still allows the other two to turn, unless an outside force (friction between the tire and the ground) prevents it.

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 The problem with a driveshaft brake is that holding any one of the three shafts connected to the differential still allows the other two to turn, unless an outside force (friction between the tire and the ground) prevents it.



Yes and understood, so the driveshaft brake can only stop one of the three shafts. Would that be the shaft with the driven (right) wheel, only? Sorry, I am still stuck on this despite evidence to the contrary. Since the driveshaft only drives the right rear wheel, how could it affect the left rear wheel?

Certainly the friction with the brake shoes and the brake drum, and then transmitted to the ground, stops the car. Realize that most cars up until the mid-twenties only had rear brakes, so the brakes need to be in perfect order at all times. 

 

The disk brake addition is to help stop a heavy car when you were in mountainous areas and riding the brakes would overheat them causing friction to be lost.

Of course of gearing down is the best idea. Except when, I think it was Pierce, in the early '30s had free wheeling and could not gear them down.

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32 minutes ago, CatBird said:



Yes and understood, so the driveshaft brake can only stop one of the three shafts. Would that be the shaft with the driven (right) wheel, only? Sorry, I am still stuck on this despite evidence to the contrary. Since the driveshaft only drives the right rear wheel, how could it affect the left rear wheel?

Certainly the friction with the brake shoes and the brake drum, and then transmitted to the ground, stops the car. Realize that most cars up until the mid-twenties only had rear brakes, so the brakes need to be in perfect order at all times. 

 

The disk brake addition is to help stop a heavy car when you were in mountainous areas and riding the brakes would overheat them causing friction to be lost.

Of course of gearing down is the best idea. Except when, I think it was Pierce, in the early '30s had free wheeling and could not gear them down.

 

The differential doesn't just drive the right rear wheel. If both tires have the same friction force with the ground, then the driveshaft drives both of them. The reason why you see only one spin (and the same one every time) is because engine torque loads the same tire every time. If you did a burnout in reverse, engine torque would load the other one. And if the brake is on the driveshaft, it stops the driveshaft from turning. So long as the force in the brake doesn't exceed the friction force between either tire and the road, then the car stops. If the friction between the tires and the road is low enough, then clamping the driveshaft can cause one tire to roll forward while the other spins backward. This is how a differential works.

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24 minutes ago, Rusty_OToole said:

There is nothing wrong with putting a brake on the driveshaft, many early cars had them (Chrysler products put the handbrake there until 1964). I wanted you to know of a possible weakness in unusual conditions, that's all.

 

Actually, there is one flaw with a driveshaft brake. If you snap an axle shaft, you have no brakes. Granted, that's not a common failure mode, but it is a flaw.

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Rusty, thank you for the video! I understand, now. It has to do with the spider gear and how the differential works! I may or not install a driveshaft brake. 

Thank you, Also joe for you both hanging in there to let me understand!

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Another consideration in the above analysis of the one wheel burn out is that static friction is stronger than sliding friction. On a perfect roadway with perfectly distributed power to each wheel , they will always break loose at the same time leaving a perfect pattern on the roadway  but the real world doesn't work that way! Once one tire breaks loose , the differential works exactly as designed , not desired!

 

As Joe points out , driveshaft brakes are only as good as the downstream connections.

Not just the axle shafts but there is also also a very important pinion to ring gear connection that can fail . Highly unlikely in a properly restored rearend but I believe a documented occurrence in well-worn Model T rear ends that have too much bearing play.

There is a reason Rocky Mountain brakes are still an easily sourced option for Model T's, especially if you have an auxiliary transmission or Ruxstell 2 speed rearend.

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There were disc brakes on drive shaft of some of the big wartime trucks. there is a 16inch diameter by 13/16th inch radially ventilated disc brake behind the joey box on a sad Federal 6 by 6 wrecker truck, which I gave to a man 15 years ago.  ( but it is still here). I also once found a few new brake discs, which by the labelling were intended for Ford or other make Jeeps, which I never had anything to do with mechanically.   Probably the earliest disc brakes 000000were on Dr. Frederick Lanchester's first horizontal 2 cylinder cars.  you can research these and many other treasures of early automobile design in the book "Automobile Design:  Great Designers and Their Work."   Last time I looked at the lists, there were excellent condition copies for around $20.   If you are wise enough to acquire a copy, study also the first chapter on the Bolle' s of Le Mans,  father and two sons.  They were responsible for a lot of original inventiveness.   We had one of these big Tank transporter rigs for 800 pounds barely new with a Rogers trailer. My father admonished one of his key employees  for "wasting" the entirety of his allocated spending money for the day on this big left hand drive Diamond-T monstrosity.   The cost it saved in cartage was enormous over the next 15 years.  The big Hercules diesel engine was slow and lazy:  "like a railway cup of tea,  big and weak." But it never collected speeding tickets, at 28 miles per hour uphill or down. The Victorian State Electricity Commission had some small number of these 6 x 4 tandem drive trucks;  but they discarded the Hercules diesels for much more modern and energetic Rolls Royce Diesel engines. They travelled at highway speed.

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Band brake. A drum type piece bolted to the yoke, transmission output. I have a 1964 Dodge D100 pickup with this type.

 

A disc could be done the same way. But I'm thinking maybe this could be adapted easier, even by salvaging some parts from a wrecking yard and adapting them.

 

image.jpeg.86dcf7fb2645c8e988daf96165ca25ea.jpegParking brake parts and advice. - The 1947 - Present Chevrolet & GMC Truck  Message Board Network

Edited by mike6024 (see edit history)
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