Roger Zimmermann

Construction of a Continental Mark II model, scale 1:12

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Cars from this time were rather simple: many parts, pure mechanical devices. Probably not all were so carefully build like Cadillacs were: for example, the lever I pictured recently was installed with a needle bearing on the brake shield. Probably cheaper cars would just have a bronze bushing for the same configuration. The solutions retained were rather logical but to reproduce them on a scale model is another matter.
As an example: I began to reproduce the large lever you can see at the right on the picture of the original assembly. It has a strange shape, but it was very ingenious: the nut at one end was used to finely adjust the brake shoes. This nut pulled or pushed a rod connected to the splined hub, modifying the position of the hub in relation to the lever. 
As my project is to make a rolling frame, many details will be seen. Therefore, I had to reproduce the splined shaft & hub. I will not add the provision to adjust the brakes, because this detail would ad too much complexity at this scale.
The question was: how to do the splines? By chance, I had a milling cutter with the appropriate width. I imagined that I could do a shaft in brass and broach a piece of brass 1.5mm thick. To my satisfaction, the splined shaft was good looking. With a pilot hub, I entered the shaft into the hole of a scrap piece of brass, put the assembly in the wise and put pressure. I saw small bits of brass and was thinking that life is good, the tool is making its way. When the shaft was through, I pushed it back and, to my dismay, I saw that the teeth were just shaved! Obviously, my solution was not good. I reluctantly took a piece of mild steel and did the splines on that shaft. Contrary to my fear, the milling cutter had no trouble to work on that mild steel.
Another hole, another test: still no good: the teeth were still there, but pushed back, creating a bulge. Not good for a part which should have a snug fitting!  I came to the conclusion that broaching can only be done with a tempered steel shaft. My milling cutter will be instantly destroyed if I make an single attempt!
Another brain storming was needed. By chance, I have a large stock of dentist milling tools; the shaft's diameter was near to the desired shaft diameter!
I removed from that milling tool what was not needed and, with a diamond covered disc, I made an approximate splined shaft which was to be used as a first pass. The definitive splined shaft would then finish the female splines.
This time, the whole process was a success. With the tempered shaft, I could do the approximate broaching; the final treatment was done with the shaft which will be used on the model. There is an inconvenient with this method: shaft and lever must be indexed and will not be interchangeable as my machining is not precise enough. This add a bit to the complexity, but as there are only 4 shaft and lever pairs, it can be done. And, fortunately, the parts are the same for the front and rear brakes. 
On the pictures, that lever is just an approximative shape. I wanted first to be sure of the broaching process before doing the final shape.

Probably Mike will also appreciate: one day to make the tool and 10 minutes to broach the four parts!

77 steel tool.JPG

78 first pass.JPG

79 the result.JPG

80 broached  lever.JPG

81 final broaching and shaft.JPG

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The next task was to shape the levers for the brake cam actuation lever. Those tiny parts required a lot of work as usual. Both parts on the right side have some dots stamped on them as reference mark for the shaft as they are not interchangeable; the line you can see is for the proper indexing for the shaft for the same reason. Once installed on the brake shields, the dots will be on the inner side, therefore they will not be seen. The pins at the end of the shafts will help to locate the cams prior to silver soldering.
I still have to add one or two details to those levers; it will then be the turn to do the bearing for the shafts. On the real vehicle, the bearing is adjustable by loosing a nut and applying the brakes; I think I will skip this feature as the brake shoes will anyway be also adapted to each drum and brake shield. Sure, this practice is contrary to the one of Mr. Leyland; the purpose of my construction is not the same!

 

 

82 brake camshaft lever.JPG

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On ‎1‎/‎19‎/‎2020 at 10:42 AM, Roger Zimmermann said:

Probably Mike will also appreciate: one day to make the tool and 10 minutes to broach the four parts!

 

The splines you have cut in the brass plate look very symmetrical to me. I can not imagine even attempting to make a broach, especially on that scale with a diamond coated disc. How do you keep it so steady when doing the grinding? As usual Roger, amazing work.

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They are symmetrical, but not exactly identical, which is the reason why the shaft and arm are indexed. I have a dividing device like you see on the picture. During grinding, the steel shaft was put in the chuck; I used the same disk as on the picture and I was taking 0.1mm each time, to avoid flexing. Since I have this small machine, I know almost each time how to do and its limitations.

It's easier to make a broach at this scale than at 1:1! Its either a hit or miss but the waste, in case of a miss, is rather limited!

102 Milling slots.JPG

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With the addition or a stud, large nut and the locking "spring" for that nut, the first actuating lever is finished. The equalization of the brakes could be done with the large nut at the end of the lever. I don't know if that locking spring was efficient to block the nut; I suppose it was the case as this system was used during some years.  Still 3 to do!

 

 

83 locking spring.JPG

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3 hours ago, Roger Zimmermann said:

I have a dividing device like you see on the picture.

 

Ah Ha Roger - I didn't realise you had cheated! :) I thought you had made the broach freehand. I had not realised that dividing heads were available on a small scale.

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Without that, it would be difficult just to make the holes for the wheel's studs. Even if I'm the advocate for only a basic equipment, some nice features are needed.

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Still working on the brake system at the shields and it's not yet over! For those who are not familiar with these very old cars (I was not myself some months ago!), the brake shield at the right is showing how the system is functioning: a cable will be attached at the free eye on the right; to brake, the cable is pulling the lever to the left. The connecting lever is moving the cam lever in the same direction.
The brake shield at the left is seen from behind. The still unborn cam will be soldered to the steel shaft and, by turning, will push both brake shoes towards the drum. Easy!
Are the brake shields ready now? Not quite: still missing is a pin as anchor for an outside return spring; both shoes guides are still unborn as well as the anchor for the cable.
The rear brakes are practically identical. The sole notable difference is the actuation of the cam lever: it's not done with a cable but with a shaft and a lever.

84 front brake shields.JPG

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 Roger, I never tire of seeing your truly amazing craftsmanship. This starts to sound like hyperbole, but calling you a "Craftsman" doesn't even do you justice!

 Keith

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On my other models, I did the brake shoes by turning a piece of brass. As only the emergency brake would be functional, I did only the rear brake shoes. On this model, I came to the conclusion that the same approach would create a lot of waste. I decided the make the shoes with flat brass. The picture is showing the parts which will eventually be shaped as brake shoes. The eight half circular parts were initially straight; to cut them with the correct shape from a brass sheet would also create a lot of waste. It took somewhat more time to shape them; time is free!
Now, I will have to shape them according to the original set-up and soft solder the sole (if that word is correct in English).
The brake system will not be a genuine replica of the original one; I have to take liberties and I'm simplifying the system. For example, the floating shoes were made with aluminum because its dilatation was greater than a shoe made with steel, therefore avoiding or retarding the fading of the brakes. I have some doubts that this theory was really effective; the fact is that later brake shoes were all made with steel.

85 Brake shoes.JPG

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Roger, I build models, and believe you me, you are an inspiration for my work. John

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13 hours ago, Roger Zimmermann said:

Glad that I can "show you the way"! John, what kind of model(s) are you building?

Roger, I build replica model cars. I like to work with resin kits. Mostly build cars from the Fifties and Sixties. I also collect Dealer Promotional models. Thanks again. John

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Ah! dealer promo models! I have some from GM...

 

Adding functionality to a scale model means that the time spent to make all the parts is increasing dramatically! As I still hope that I can have a model with a functioning service brake means that all details must play together.
After soldering the brake shoes and trimming them, I began to "install" the anchored front shoes (one per side). I did first a large flat support onto the shoe will be anchored. The other side of the shoe is in contact with the cam. By turning that cam, the drum should be stopped. First, I trimmed the free end of the shoe until the drum could be turn more or less freely. Then, I silver soldered the cam on the shaft I showed some time ago. Then, the test: yes, the drum can be stopped with a rather mall movement of the external lever (the one on which the cable will be attached).
The next task will be to trim that flat plate and prepare and fabricate what's needing for the floating shoe.

As the rear brake shields are different, the rear brakes will be done later, probably when the rear axle will be available to position the shields correctly.

86 Anchored shoe.JPG

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Even if I'm simplifying the brake system a bit, I was faced with a specific problem like "how to avoid that the axles are dislodged?" By soft soldering a washer at the end of the shaft can be a solution (with the risk that the next part is soldered too), but how to do in case something unexpected is happening and the shaft must be removed? Finally, the solution used on the real car is the best I found and I will follow this idea. The next problem was: how to cut a groove 0.3mm wide? By thinking a bit "out of the box", I used a cutting mill, attached it firmly and approached it to the axle. By turning gently, I could do a groove deep enough to inset a similar part like the original.
I'm adding a picture from my machine set-up and one from the original system; the axles are for the link on the right side; the arresting plates are attached with one screw each. This is what I will reproduce.

87 Machining  a groove.JPG

IMG_5946.JPG

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Roger, I am a 'bit lost' as to what the problem is, and what you are trying to achieve? It's probably me, but I have read the last two posts through a couple of times and I still don't understand. Is it the inward side of the axle that you have in the lathe chuck that you are machining the groove in?

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Now, you see what are my limitations in foreign language! I'm trying to explain differently: you see at the second picture the aluminum shoe and the link attached to it. That link is also attached with an axle to a stationery plate. The system used by Cadillac (and maybe other brands) was to do an axle with a shoulder, connect the needed parts with that axle. To avoid that the axle will go out, a groove was machined at the small end of the shaft and a retainer (a flat metal part) is entering that groove. The retainer is itself screwed to the link.

What you see on the first picture is the method I'm using to do the groove; once ready, the axle will be cut away from the bar. The slightly diameter will be the needed shoulder. To do that groove, I had the possibility to make a stationery tool with the required width. Too complicated for just 8 shafts; therefore I took a milling cutter and attached is solidly to the toolholder. (usually those milling cutter are turning and are not stationery)

I hope that my explanation is making sense!

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I don't know if Mike understood my second explanation better. If not, I'm showing in pictures what I'm doing. First, the parts, especially the axle with the groove and the plate which will be engaged into the grove. Then the assembly, which took about 10 minutes to achieve because the small plate had no envy to stay in place.
A similar plate will be installed at the other end of the link.

88 link's axle.JPG

89 assembled link.JPG

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Roger, I believe the word "axle" may have thrown him, it did me. I assumed you were referencing and actual drive axle when what you were referring to is more or less a "pin", at least to me.

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Again, a translation problem! In French, we are using the work "axe" for all kind of shafts, axles or pins. I agree, the word pin would be more appropriate.

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Roger do you know what doesn't suffer from a translation issue, the photos of the incredible work you do.  😉

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