- When it comes to retaining the wrist pin inside of the piston,
there are a variety of techniques available.
Probably these days, particularly in the sport compact market, the techniques
that we're most used to would include wire locks, spiro locks,
and perhaps cram locks.
However a technology that's certainly not new is to use a button instead
in order to retain the wrist pin.
Now we're here with Dan from Diamond Pistons to talk about their own button
design and exactly how that works.
So Dan first of all, these buttons as I've just mentioned, they're not new,
they've been around for a long time but we don't see them that often,
particularly in the sport compact market.
Can you tell us where the advantages of the button lie?
- Yeah absolutely so the advantage with a pin button is more so that it's
a captured style, so it rides against the outside of the cylinder wall,
completely stopping it from being able to move anywhere.
We manufacture it to the point of where the outside radius of the piston,
perfectly machined so it rides against the cylinder wall with no issues there.
When the pin tries to have outward movement, or it tries to rotate,
the button completely captures it to stop it from going anywhere.
It's not gonna damage the cylinder wall because of that so there's no end play
on the outside of it.
- So I think most people can probably understand with a button on each
side of the piston, there's literally nowhere for that wrist pin to be able to get out.
But of course with a conventional, let's say a wire lock,
as long as that wire lock's been installed correctly, it's still a relatively reliable
installation method so can you talk to us about some of the disadvantages
with the wire locks, spiro locks, and cram locks, and how they
potentially can cause issues?
- Sure absolutely so with any lock there's always the potential for failure.
With the wire lock if it's cut into the groove or it has excess motion on the
outside of it, it could cut its own groove, it could beat itself out of the lock,
but that's also if there's poor oiling in the pin bore or anything like that.
When it does that, if it pushes its way out, it could fall into the pan,
it could cause catastrophe.
With the pin button though, it's completely stopping it from doing that.
The oil ring actually holds it in place so it can't rotate, it supports the oil ring
from underneath too if there's ever a break in the ring land stack there.
- Alright let's just talk about that oil control ring as well because with your
pistons, as you've kind of alluded to there, the design of the piston is that the
pin button does intersect with the oil control ring.
So that's a critical part because it stops the pin button rotating?
- Correct yeah so with that oil ring sitting there, the pin button actually has a flap
cut into it to stop it from moving in any which way.
We also can do it with a support rail as well which is a steel ring that goes on
top of it so you can have even more support under that oil ring.
The whole reason we do that is that when we drop the ring stack down,
we have to get as much material up there as possible, turbo application,
nitro application, you put a lot of heat into the crown of the piston so we try
and drop it down as much as we can and when we do that we end up
intersecting into that pin bore.
The reason with the button is that not only do you get that material you
took out, but then at the same time, it's aluminium, it's not gonna go anywhere,
the steel support rail does work very well but at the same time you're
getting two benefits at one.
- Alright just wanna talk a little bit about the location of those ring packs
you've just mentioned there.
So conventionally we do see the oil control ring intersecting the pin boss
in a lot of designs but typically this is where the compression height of the
piston has been reduced to accomodate a longer connecting rod.
But what you're saying here is you're doing this anyway naturally,
even with a stock compression height, you are dropping that ring pack
down on the piston?
- Yep that is correct and the whole reason we do that again is just for power
application.
So the more surface area you have on that piston, the more heat it can take,
the less likely it is to fail.
And it's not just the top land either, so the second land also needs to have
a lot of material on it to support that ring.
When you're putting in 40, 60, 80 pounds of boost into the top of the piston,
you need that support underneath that top ring and you also need the surface
area as well to be able to handle all that heat.
- So this essentially becomes more critical with power adders that basically the more
power you're making, the thicker you want those ring lands to be.
- That is correct.
You'll see in a lot of naturally aspirated applications where they'll have a real
short ring land, the reason is is they want as much heat as they can in that
piston to increase that combustion effort.
With the big power adder stuff you don't need that, especially with the fuels they run.
If they're running anything with methanol or anything like a pure racing fuel,
again you're generating a lot of heat, you're putting as much timing into it
as possible, the likelihood of that aluminium flexing, even warping,
burning a hole through it, you need as much material there as possible.
- So if you're in a situation where you've got a client that is running a power adder
forced induction and they also wanna run a longer rod, is this a situation where you
kind of need to make some compromises with the piston design in order to
basically just fit everything in.
- That is correct yeah so the longer the rod you go, you're sacrificing integrity
of the piston so let's say you could run like let's say an inch 200 compression
height on a standard rod length.
You go to a longer rod, let's say like a plus five or something like that,
that's very common, you end up putting that in there and now the piston is
shortening up that much more.
What you need to worry about when doing that is now everything is
intersecting, I can't put as much ring land into it, I can't put as much ring
into it so everything's effected.
If I could run like a 1.5 millimetre top ring, now I have to run like an 0.43
or a one mil.
All that, if you're doing a power adder, especially you're putting more heat
into that ring, it can fail because there's less surface area.
- Now actually you've just mentioned the ring thickness so I just wanna dive
into that a little bit more because we have seen a drive with aftermarket piston
manufacturers, ring manufacturers over the years, where the ring packs have become
thinner and thinner.
And my understanding on that is the thinner the ring, it reduces the
frictional losses.
But you've just mentioned there can be some advantages with a thicker ring
so can you just talk to us a little bit more about that?
- Yeah absolutely so the thicker the ring the more heat it can handle.
Most of the rings that we use are steel top rings anyway.
But if I could put a 1.5 millimetre or an older, like 1/16th top ring in it,
that ring is gonna be able to take that much more heat just because of the
surface area.
As it dissipates, having the larger area, it's gonna move into that crown of the
piston from the ring.
So the bigger it is, the more it can take as far as heat putting into it.
It also helps with structure as well, so if you have a thicker top ring,
especially with the depth and everything like that, you're gonna be able to put
a lot more on top of the piston, whether it be nitrous, again turbo,
supercharger, whatever it may be, and it's gonna be able to support
that boost.
With a smaller ring, when you get into the one millimetre, even in some
the 0.7 stuff where all that frictional loss has gone.
In a naturally aspirated application, sure, it's great, it's gonna help the piston move
freely in the bore.
But at the same time if you put a lot of power into it, the likelihood of it
flexing and kneeling or trying to butt the ring ends together, it will fail.
- Alright just moving back to those pin bosses or buttons I should say there,
your ones obviously as we've talked about are made out of aluminium,
and I know that probably a technique that was used back in the day was to use
a teflon button.
Can you talk to us about the advantages of the alloy over a teflon?
- Yeah with the aluminium it's the same thing.
So as we machine it when we have the tolerances the way that we have them,
if it's machined properly it should never move, it should never flex.
When you put something like teflon in there, yes it's gonna glide well but at the same time
it doesn't have the same type of structure as something that, like an aluminium part
would so we use that to make sure that at that time, the oil ring can't go anywhere,
there's not gonna be any flexing, failure, any of those thing happening.
- I think probably another aspect is that most people would consider the teflon
material's gonna basically do no damage to the bore wall but as you've sort of
alluded to earlier in this interview, the aluminium buttons that you
produce actually don't end up contacting the bore wall.
Basically they are supported on that oil film, is that correct?
- That's correct, the other thing too is you have to think, the actual piston
itself where it is contacting the bore is aluminium.
If it's set up properly and you pull a piston out and the bore looks OK,
that has force on it from either a compression stroke or something
like that with a button just riding in the outside of the walls where
there's oil coating it.
There should be no contact issues or failures.
- Look great to get some insight into those buttons, thanks for giving us a
bit of a description on how they work.
If our viewers wanna get a little bit more information or reach our to Diamond,
how can they do so?
- Yeah you can go right to our website, it's diamondracing.net or you can
even email me, it's dfonz@diamondracing.net
- Awesome thanks for your time there Dan.
- Thank you so much.
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