Unimaginable Tire Molding
Difficulties
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----I see. Well, as someone who loves the 88 and 91 to
death, I’d be crestfallen myself if their commercialization isn’t realized (chagrin),
so I’ll try not to get my hopes up while I hold my breath.
That aside, there’s
still one thing I’d like to ask you while we’re here today. I’ll come out and say it, but I’m not very
satisfied with the any of the tire shapes in Ebbro’s 1/20 F1 models. I’d really like to ask how that could happen
with guys who’re considerably picky about tire shapes, you Kiya-san paired with
Sugiura-san, and what’s so difficult.
… It’s differing processing methods. With Tamiya, the rubber tires are processed
using beryllium, but that way of doing it generates pollutants, and the number
of contractors who’ll take on that work around the world now is very
limited. Besides, the costs are absurdly
high.
So indeed, I’d like to use rubber tires
with Ebbro’s plastic models too. Because
you don’t get this hard dry surface texture with rubber tires, and the tires
have both this soft feeling and a sharpness about them. But there are various limitations on that, so
we can’t do it.
----… Ah, in
other words, Ebbro tires aren’t made of rubber?
It’s in what’s called the elastomer family,
and it’s a kind of plastic that has the springiness of rubber. Elastomers pull back a lot, and have you have
what’s called a high shrinkage ratio when you injection mold, so it’s not easy
to get them to come out as you imagined them in the blueprints you drew. If you do it wrong, 1/20 tires can shrink up
to 1mm or more. And we didn’t really
know that, honestly speaking.
Added to that, with us we cut out a tire
master, and use electric discharge machining with an electrode while turning
that. But as you’re doing that, the
surface of the master slowly wears away, and eventually you wind up with a
somewhat smaller diameter that you hadn’t calculated for.
----But if you
turn that around, now you know that “They’ll get smaller if we do it the usual
way”, then surely at the design stage you can…
Yeah, we’ve already thought “Well, let’s
just make them a little bit bigger”. We’ve
tried that, but then they don’t come out uniform. There’s variation. And if we plan for the pull-back and make
them bigger, they just come out that way too (chagrin). It’s been tedious. We really can’t see what the conditions are
when they come out small, and when they come out as-is. So we struggle with that every time, actually,
and it’s always like “Do we redesign them 1mm bigger, or try going through the
processing once more?”
----So, is that your biggest problem right now?
Yeah, it is. It’s still the tires. Nevertheless, we paid a lot of attention with
designs for the Lotus 49 from the start, so I think we were able to do the
millings rather well.
----The
shoulder lines on the 49’s tires are certainly sexy, aren’t they.
Yeah but our tires before the 49 were
rounder in blueprints, and did have the proper profiles you know.
----Well you
know, I’m probably the only one complaining about the tire shapes so much.
Yeah, you are. You’re the only one, Asano-san! (laughs)
----With
regular boxy cars or sports cars, the tires aren’t exposed, so you don’t notice
the profiles as much, as long as you handle the tires’ ellipticity right. But with Formula cars…
Yeah, that’s right. But our next products should be much
better. We’re slowing coming to see the
conditions we need, and things are progressively getting better. In other words, our experience level is a bit
lacking, with regards to electric discharge machining for elastomer
molding. But we’re also meshing with our
contractors, and since neither of us will do anything until we both understand
what the other one wants, our experience levels are building, and things can
only get better. It’s not easy you
know. These are new trials for us, after
all. But once we have our processing
methods established, I think we’ll be able to see our goals.
And, since we should be able to do our tire
injection molding as expected soon, I’m thinking about remaking some of the
tires then. When the best shapes come
out, I’ll commercialize some extra tires to be sold separately.