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Roy vd M.

Fiat 806: research and scratchbuilds

3,434 posts in this topic

Chaps,

 

I for one am still following. Not getting much time at the moment though. My focus has been on the steering arm. I think I have a shape that is plausible but there are so few sources. I'll share at some point.

 

I certainly watch the ongoing progress with interest.

 

On the handbrake mechanism, I understand why it might look like a short rod but I have felt for a while that it is a geared mechanism. Oliviers photos above are key. It looks like there is no clearance between the bar with the star-wheels and the long handle. Drawing 2 suggests teeth in this area. Three of the pictures above suggest that too - a little spike is just visible at the 11 o'clock position. Thoughts?

 

Nick

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Posted (edited)

Dear Nick , on drawing 2 ( top-view ) I cannot see gears . If there had been gears  they  only should work if the handbrake is pushed forewards imho .

I guess there was a spring which brings back the handbrake to a neutral position .

There also must have been an arrest function but I´m not sure how it worked.

I still believe there was a short rod or wire because there´s also a nipple on this bar as we can see for the two other brake wires 

Many greetings !  Hannes

Edited by Hannes
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Posted (edited)

Thanks for the drawing, Hannes, and thank you to Harvey and Nick. It will be more simple to cement the little rods on ever glued 2 mm tubes. I take a lot of care to get precisely the same lenght for my 0,6 mm rods (3 mm, I recall, the first ones were too long, about 4 mm, while the kit's ones are only 1,5... I would prefer to cement little balls than the resin option, but the kit's ones are not so good. Maybe I will use homeopathic granules, half sucked, as I did on my Chevy Bel Air to represent the gearshift knob... I would prefer to use little steel balls of the good size, but where to find them?

About Robin, he had brought a new life while the enthusiasm began to decrease seriously on thread. Now he has stopped posting, we feel often very lonely.

Hannes, I am study with care your drawings, if Fred or someone else could bring opinions, or better, photos of this kind of braking system, it would be great... 

Edited by Olivier de St Raph
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Posted (edited)

2 hours ago, NickD said:

Chaps,

 

I for one am still following. Not getting much time at the moment though. My focus has been on the steering arm. I think I have a shape that is plausible but there are so few sources. I'll share at some point.

 

I certainly watch the ongoing progress with interest.

 

On the handbrake mechanism, I understand why it might look like a short rod but I have felt for a while that it is a geared mechanism. Oliviers photos above are key. It looks like there is no clearance between the bar with the star-wheels and the long handle. Drawing 2 suggests teeth in this area. Three of the pictures above suggest that too - a little spike is just visible at the 11 o'clock position. Thoughts?

 

Nick

Thank you Nick, I agree with you, I think there is a kind of gear between both parts. I see a cross on photo 28 and photo 1. I admit things are less evident for me on Drawing 2. But in the same time, I see now the thin rod Hannes mentions, on the upper part. For now, things remain unclear for me. In the lack of new info (hope we will get something), I will represent the cross I see and just talked about. The question with the thin rod is: where does it go precisely? Isn't there a relation with the reinforcement that is frontally situated/ handbrake?

 

FuWwE8.png

Edited by Olivier de St Raph
correction
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The cross I see, kind of gear between both elements?

hOehF6.png

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Chaps,

 

I have not had time to devote the attention to this that it needs.

 

One thought though - for me the key is the bottom cable (that goes to the front wheels). It seems to have a long rod out of the opposite side from the cable too. It looks to me that these knurled elements are tensioners for the cables. The rod is just part of that adjuster. If the handbrake operated on this then the tensioning mechanism for the rear would be different from the front which would be complicated.

 

If it is geared it is puzzling too. Pulling the lever towards the driver would pull the rear and front brakes on. Braking normally would cause the handbrake handle to move which would be wierd. Presumably the button on the lever would lock the mechanism in some way.

 

Regards

 

Nick

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Olivier,

 

That is how I see it too but as I have just noted, some of the details of how it works are unclear to me.

 

Nick

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Once again Fred is required with his profound technical knowledge . Black knight , please appear in the night ! :D  Hannes

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Posted (edited)

I read some descriptions about hand brake systems in wikipedia . A gear system is not mentioned but cables seem to be usual for drum brakes .Of course today sometimes handbrakes are used for drifting but I doubt this regarding our car . A gear system could cause trouble imho and for a parking brake a single cable should be sufficient ( maybe similar like my drawing on the last page )

I guess parking brakes were prescripted  for racing cars at that time to prevent a rolling downhill in case of an accident or breakdown . I agree regarding the knurled stars as tensioners . To prevent the handbrake from moving  simultaneous with the levers  a similar system as shown  on my drawing could work .  Hannes

Edited by Hannes
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Posted (edited)

I prefer this 2nd version, with shorter (about 3,2 mm) and thinner rods (0,6 mm brass tubes). Now I like my stars... Notice that the balls were either taken from the kit (black ones, after trimming...), either homeo granules sucked until I get the good size (1 mm here). I should order steel marbles of different sizes, the result would be still better...

f4jyZk.jpg

Edited by Olivier de St Raph
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59 minutes ago, NickD said:

these knurled elements are tensioners for the cables.

I agree, Nick, I think they are tensioners.

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Dear Olivier , please wait with mounting these fragile parts till the end of your construction ! They can get damaged or lost very easily and you will still have to work on the exhaust pipes !  Hannes

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I've looked at the photos on page 1.

Photo 1A - the brake rods have been airbrushed out

1AA is better

3 shows the lever full forward

28A shows the lever angled forward

Photogammetry 1 is of two images, one overlaid on the other; one has the lever fully angled to the rear - where does that image come from?

Ignore all of the drawings - they all have errors

 

1; remember these brakes are totally mechanical. Hydraulic brakes are of the 1930s and I do not see any evidence of hydraulic brakes on this car.

Being mechanical the braking effort is dependent on the strength of the driver - his leg or arm, or both

 

2. Is there a locking button on the top of the lever? Possible, but not probable. I think what we see is the top if the metal shaft above the thin rubber hand grip.

 

Taking point 1. It appears that Fiat is clever. By using gears they can multiply the driver's arm forces to the brake system.

Pull the brake handle to the rear; the gear teeth on it go downwards, counter clockwise - the gear in the rod linkage rotates downwards, clockwise, the top linkage is pulled forwards, and the bottom linkage is pulled rearwards, both pulling on the brakes

 

Point 2; it was more usual to have another lever attached to the main brake lever. This smaller lever releases the dog, or pawl which engages in gear teeth and locks the lever on or off. I cannot see a locking mechanism on this brake system

The handbrake system on a 1928 Bentley 4.5 litre racing car; the small lever can be seen at the top

Bentley%20brakes%2001s_zpsoursjaiy.jpg

[sorry, best photo I can find right now]

 

3. Actuating the brakes via the foot pedal does not move the handbrake lever. The systems are independent but within each other - by the use of counter shafts.

On my 1930 Austin saloon [a car not mentioned till now]  the foot pedal is attached to the rear brakes via a shaft across the chassis, off which the brake cables run to the brake drums. Over this shaft is fitted another hollow shaft which has the cables to the front brake drums. Applying the footbrake pulls on the rear brakes, only them, as this shaft rotates, within a counter shaft. When I pull on the handbrake lever the outside counter shaft engages the inner shaft and pulls on both the rear brakes and the front brakes

 

4 In this era front brakes were considered to be not needed or not very effective. The first car to offer 4 wheel brakes as standard fitment was the Austin 7 in 1922, from 1924 other car makers offered front wheel brakes as an extra feature for more money

But - racing drivers new how effective front wheel brakes are and had them on their cars and used the hand brake lever more than the foot pedal. In our club racing and events we use the hand brake lever more often than the foot pedal

 

5. The adjustment of the tightness of the rods or cables are the thick parts poking out in a line with the rod or cable. This takes up the slack and determines how quickly the brake will come on, it takes up any slack in the cables stretching through use; they can stretch 10mm during one race.

The stars are the tensioners, for how tight or loose the mechanism works. Too tight and the driver needs extra muscles to pull on, too loose and he can't do a fine measured amount of smooth braking

 

I think that covers some of it

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This is an very profound answer dear Fred , many thanks for that ! Now we know the stars did not tighten the cables and much more ! Have to read again  till everything is clear for me

Many greetings !  Hannes

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Posted (edited)

7 hours ago, Hannes said:

Dear Olivier , please wait with mounting these fragile parts till the end of your construction ! They can get damaged or lost very easily and you will still have to work on the exhaust pipes ! 

Dear Hannes,

it is a very good hint, that I will follow indeed. 

Thank you Fred, your post is very helpful, even if I still don't know if the cross I see is a gear or not. What is sure now, I will represent the little rod that Hannes mentioned, on the top, connecting the handbrake with the set "tensioners", as we can see on the Bentley.

Another question I am wondering: on Robin's hint, I have ordered a very nice 0,38 mm braided wire, to represent the brakes wires, but on all photos (Bentley, Fiat Mefisto, Delage, "master model" etc.) this wire looks like a metal not braided rod (the kit offers a thick spring). Finally, I am not sure the braided wire from RB Motion is the best solution. More, it will not be easy to get it very tensioned, as it should be. I could use this braided wire for the curved portion going to the front wheels (139D) but use another solution for the straight portions, a thin rod or tube (size to determine). I would like your opinion about that question (Fred, Hannes, Nick and others if possible).

I post again a photo of the Mef to show what I mean. I had posted it to show the fixation system, but we can see also the beginning of the cable going frontally. But Fred's photo of the Bentley shows the same rod...

ydB4Sc.png

 

Edited by Olivier de St Raph
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Hannes, have a look (with magnifiers) to the 806 on p. 145. The little cable stops frankly before the handbrake!! This build will turn us mad... Not time now but I will post an enlargement of this HR photo...

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Because the rod or cable is at an angle to where it affixes to the lever mechanisim [see top one] I think it might be a cable; a rod would need the fitting in a direct straight line

Also the 'tail' of the bottom one curves down it might also be a cable

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Posted (edited)

Dear Olivier  this " interrupted " cable is an effect  of a reflexion on the polished handbrake stick in my opinion . 

If you want to tension your cables , make sure the cross-rod does not move anymore  by glueing it to the chassis rails . Remove  the  cramps for the springs   and drill tiny holes instead.

Now one end of the cables can get glued in one of the holes of the small rear levers  . Wait till there´s a firm connection , cut the cable to the required lenght , add glue and insert into the hole on the central lever . To make it easier I recommend to drill the holes on the central lever as deep as possible .

I would wait with these measures till you added the exhaust pipes .

Many greertings !  Hannes

Edited by Hannes
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1 hour ago, Hannes said:

Dear Olivier  this " interrupted " cable is an effect  of a reflexion on the polished handbrake stick in my opinion

Dear Hannes,

I must say the more I see this enlargement, the more it is difficult for me to agree with your opinion on that point. It even seems to be a kind of bulge at the bottom. The problem for me is that all other photos (28, 3, 1) on which we can see it are not HR, and I wonder if it is not the contrary, the cable would seem to go up to the handbrake, but in fact, the low definition of these docs would mislead us... It is on this photo 2 HR that this area is the neatest. Up to someone proves me the contrary, I will represent this cable as I see it there. 

Olivier

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Dear Olivier , why should a cable hang in the air ? If this cable was interrupted the gap should be even greater on photos 1 AA and 28 .That´s not the case . If you elongate the downside of the stick you will see it´s just a relexion of the polished stick . 

Many greetings !  Hannes

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Ok Hannes, you convinced me. I see the continuation of the stick and indeed it is hiding the front part of the cable. Thank you!

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Posted (edited)

I have just ordered steel balls of different sizes (1 mm, 1,5, 2 mm, 3 mm) on ebay. So, I will replace the ones I glued at the bottom of my stars (I will use the 1 mm ones). No doubt that with such perfectly round balls, the stars will look better...

Furthermore, I have emphasized the line that hides the cable on the photo 2 above. Hannes, do you remember when you told me the screen was not under but over the steering wheel rods? I was very sceptic first, but looking better, I had to admit you were right. This story of cable reminded me that memory. It seems to be years ago, because so many things happened on the thread then, but it was just 8 months ago! ;)

 

P.S: thank you for your drawing above, that will be definitely very useful...

 

6SutNx.jpg

Edited by Olivier de St Raph
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People say the time runs faster when we get older ,So many things happened in a short time when we were younger . 

That proves : Our hobby makes us young again !  Hannes

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