E
Ed Price
Guest
I happened to come across an interesting concept for brake drums. The idea is to
ventilate the drum / shoe interface by drilling a number of small holes through
the drum wall. Here a site with some pictures and a discussion:
http://www.chtopping.com/classictruck.html
Drums are cast iron, so they're not difficult to drill. The holes appear to be
about 1/8" diameter. The only concern is that you drill a staggered pattern and
that you distribute the holes radially to avoid unbalancing the drum.
So, why do this? The truckers and rodders are doing this to achieve disc-like
performance without having to go to a disc system. (Many of their older and
custom vehicles simply don't have a conversion kit available.) When a disc can
be added, the un-sprung weight penalty is severe.
The advantages they talk about would eliminate the legendary "fade" that drums
are plagued with. (When you brake very hard with a drum, the shoe lining begins
to "float" on a thin hot gas layer against the drum face. The effect is like
somebody squirted oil in your drum! And you don't get braking effect again until
the lining cools down.)
They also mention, just in passing, that water is shed out of a wet drum much
better with the drilling. Now that caught my attention!!
Now, Amphis don't do much hard braking after speed runs on the desert floor, but
we sure do like to have the brakes work at the top of the ramp! How many times
have you had to remember to drag your brakes to dry them out? This might be a
very smart modification.
The only down side I can see is that you want to do the drilling job correctly.
So that means carefully marking a distributed hole pattern, not just grabbing
the drill and punching some holes! (Even so, since Amphis don't move at Porsche
speeds, balance isn't quite so critical.) Also, you will be eliminating a small
amount of drum metal, so the drum won't soak up as much heat as before (but I
think the ventilation will more than offset that). Probably the most frightening
part is contemplating drilling holes in those scarce Amphi drums!
So, what do you think?
Ed
El Cajon
67 Rust Guppy
[Non-text portions of this message have been removed]
ventilate the drum / shoe interface by drilling a number of small holes through
the drum wall. Here a site with some pictures and a discussion:
http://www.chtopping.com/classictruck.html
Drums are cast iron, so they're not difficult to drill. The holes appear to be
about 1/8" diameter. The only concern is that you drill a staggered pattern and
that you distribute the holes radially to avoid unbalancing the drum.
So, why do this? The truckers and rodders are doing this to achieve disc-like
performance without having to go to a disc system. (Many of their older and
custom vehicles simply don't have a conversion kit available.) When a disc can
be added, the un-sprung weight penalty is severe.
The advantages they talk about would eliminate the legendary "fade" that drums
are plagued with. (When you brake very hard with a drum, the shoe lining begins
to "float" on a thin hot gas layer against the drum face. The effect is like
somebody squirted oil in your drum! And you don't get braking effect again until
the lining cools down.)
They also mention, just in passing, that water is shed out of a wet drum much
better with the drilling. Now that caught my attention!!
Now, Amphis don't do much hard braking after speed runs on the desert floor, but
we sure do like to have the brakes work at the top of the ramp! How many times
have you had to remember to drag your brakes to dry them out? This might be a
very smart modification.
The only down side I can see is that you want to do the drilling job correctly.
So that means carefully marking a distributed hole pattern, not just grabbing
the drill and punching some holes! (Even so, since Amphis don't move at Porsche
speeds, balance isn't quite so critical.) Also, you will be eliminating a small
amount of drum metal, so the drum won't soak up as much heat as before (but I
think the ventilation will more than offset that). Probably the most frightening
part is contemplating drilling holes in those scarce Amphi drums!
So, what do you think?
Ed
El Cajon
67 Rust Guppy
[Non-text portions of this message have been removed]
