rear drum brake cooling device

julian

julian

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Location
Belgium
Anyone wondered how effective the cooling fin/fan design is on the drum brake Laverda?

Just done an experiment on the lathe with the hub spinning at the equivalent of 180kmh

I could not feel one tiny bit of airflow caused by this device what so ever,
Even using a heavy airline to simulate airflow over it from forward movement there was not enough air movement to move a piece of paper.

Quite disappointing!

Julian
 
It would be counter-productive to over cool a brake, as anyone who's used racing linings will know.
The cooling system should function, most likely, when the drum outer temperature is greatly elevated, the scoops on the fan assisting the convective current dispersing radially from the rear hub, the front depending on dynamic pressure to do the same.
 
Gone blank, fan? I remember seeing fins on the rear drum on my 3c but what is this fan of which you speak? And why do I sound like a character in an Arabian Nights movie?
 
julian said:
Anyone wondered how effective the cooling fin/fan design is on the drum brake Laverda?

Just done an experiment on the lathe with the hub spinning at the equivalent of 180kmh

I could not feel one tiny bit of airflow caused by this device what so ever,
Even using a heavy airline to simulate airflow over it from forward movement there was not enough air movement to move a piece of paper.

Quite disappointing!

Julian
Click to expand...
With all your spectacular efforts, I wouldn’t consider using that heavy lump in the rear wheel..

Marnix
 
Hi Marnix,
Well now I may not be, :ROFLMAO::ROFLMAO:
I did think it was rather a nice brake, heavy yes but quite well designed,

The cooling idea to run air through the drum but not via the shoes so allowing it to work better in the wet was quite ingenious, but in testing no airflow showed up that I could measure. Thinking about it, @1500 Rpm a fan that size would do very little anyway I think.
I did not do the test hot but I really doubt that would make anything more than a tiny difference.

Will maybe organize a Yamaha TZ rear drum brake then to match the front. however I feel that the Laverda twin leading shoe could have been potentially better, Where brakes are concerned, having extra meat to dissipate heat is not a terrible thing.

I'll report back,
J
 
Those TZ 4 leaders are scary enough on the front, with the extra push from a size 10, modulating would be tricky.
 
The 3C (and early 750?) rear drum in an excellent brake. It deserved the name Super Freno. It was almost too good. Quite easy to lock the rear wheel with a touch of the pedal. Way better than the disk brake setup that replaced it.

I've also wondered about the effectiveness of those little "turbine blades" on the hub. I'd have been surprised if they had actually done much. They're just too close to the hub to achieve anything. Fan blades (whether centrifugal or axial) work best when they're on the outer edge of the spinning thing. Besides, wouldn't they need air relief holes in the brake plate on the other side to be able to shift air?

It always seemed to me that those little blades were facing the wrong way anyway: trying to scoop air into the brake, which is against the natural flow of things when you think about how a centrifugal fan works. If they were facing the other way, they might have some effect as a centrifugal fan, sucking air out of the brake hub. Perhaps not much air, but enough to suck the dust out.
 
Dellortoman said:
The 3C (and early 750?) rear drum in an excellent brake. It deserved the name Super Freno. It was almost too good. Quite easy to lock the rear wheel with a touch of the pedal. Way better than the disk brake setup that replaced it.
Click to expand...
The rear drum is a twin leading shoe unit, so works well at retarding forward motion. However it is not so good at preventing the bike from rolling backwards when stopped on an uphill incline.

cheers,
bazzee
 
julian said:
Will maybe organize a Yamaha TZ rear drum brake then to match the front. however I feel that the Laverda twin leading shoe could have been potentially better, Where brakes are concerned, having extra meat to dissipate heat is not a terrible thing.
Click to expand...
I quite like the Grimeca rear drum of the 750S because of its low weight, availability of sprockets and transmission damper rubber (they were used in many other Italian bikes, which usually had 40 spokes but were for the rest identical), and it brakes just fine.

Marnix
 

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bazzee said:
The rear drum is a twin leading shoe unit, so works well at retarding forward motion. However it is not so good at preventing the bike from rolling backwards when stopped on an uphill incline.

cheers,
bazzee
Click to expand...
Rolling backwards, on an incline, I want both feet available, so would always go with the front brake for retardation.
 
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