Water cooled 4 Stroke?

[Andrew Hartz]

I'm looking at building an R/C boat this winter to be powered by an OS
0.91 Surpass 4-stroke. I realize this is an air group, but I'm hoping
someone here can help me brainstorm a little bit about how to keep the
engine cool without propwash.

Obviously, the best choice would be to use a water cooled head like the
purpose-built marine engines use. I am, however, hesitant to chuck a
$200+ engine in an end mill and start hacking. I had originally planned
on using a clamp on water cooler much like is sold for Cox .049's, but
I'm having a hard time figuring out how to do it and stay out of the way
of the intake, exhaust, and pushrods.

The engine's head will be fully exposed in the hull and will get a LOT
of airflow as it runs around the lake, but I'm not sure that it'll get
enough cooling, even at 40-50mph.

Any ideas?

Andy
http://wwh.net/iwrc/

[Robbie & Laura Reynolds]

I seem to recall that OS made a water cooled 60 four stroke
several years ago.

Robbie
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[Garnet Brace]

In article <365A0C6A...@earthlink.net>, iw...@earthlink.net says...

>I'm looking at building an R/C boat this winter to be powered by an OS
>0.91 Surpass 4-stroke. I realize this is an air group, but I'm hoping
>someone here can help me brainstorm a little bit about how to keep the
>engine cool without propwash.

.. snip
>Any ideas?
>Andy

How about having a look in the helicopter parts bins and picking out
a cooling fan and adaptable shroud. You could even get a centrifugal
clutch so the boat won't be moving all the time.

A friend wrapped a foot or so of about 1/8 inch aluminum tubing around the
fins on the cylinder below the head and runs water through it. I saw it
running a round the lake for a few minutes. Seemed to survive OK.
This was an old pre-surpass OS 40 which he was prepared to sacrifice
if necessary. It still has compression.

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.... Garnet
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only replace the * with @

[Andrew Hartz]

Garnet Brace wrote:

<< How about having a look in the helicopter parts bins and picking out
a cooling fan and adaptable shroud. You could even get a centrifugal
clutch so the boat won't be moving all the time.

A friend wrapped a foot or so of about 1/8 inch aluminum tubing around
the fins on the cylinder below the head and runs water through it. I saw
it running a round the lake for a few minutes. Seemed to survive OK.
This was an old pre-surpass OS 40 which he was prepared to sacrifice if
necessary. It still has compression. >>>

I had thought about using a fan from a small Radio Shack electronics 12V
DC fan ... reboring the hole, balancing it, and mounting it in front of
the flywheel. What turned me off from this was that the fan would sap
power from the engine. How much would it affect the boat's
performance? You tell me - but, I figure every little bit of lost power
has to add up somewhere. I would reallyreally like to use water cooling,
but if no other simple option presents itself, I'll look into a fan.

How hot does your friend's engine get? If he's willing to talk to me,
please pass along an email or phone # where I can reach him.

I'm heading to the hobby shop tonight to check out the OS they have on
display to see if getting a copper or aluminum coil around the head is
feasible. I may be able to do it by "dremeling" away some of the fin
around the pushrod and intake. This doesn't concern me as much as
putting the whole thing on a lathe....but maybe it should. :)

A fellow boater modified a Saito 1.50 for water use by working over the
cylinder head to add a cooling ring (similar to what is done on
marine-modified-Homelites). You can see a picture at
http://wwh.net/iwrc/Pics/MH_4s-8.JPG (not the best view of the head, but
you can see that the fins are filled in). The Saito engines look like
they've got a "rounder" cylinder head that would lend itself better to
modification this way. I had decided upon the OS engine basically
because of the $40 merchandise rebate currently in effect, but may
rethink this decision. Hopefully the local shop hasn't sold their Saito
.91.

Thanks for your help,
Andy
http://wwh.net/iwrc/

[Dean]

You can easily mount a 2-3" high pitch prop with a pully to connected
to the drive washer/shaft. Adjust fan size accordingly (gross
figures).

-Dean

On Mon, 23 Nov 1998 20:31:22 -0500, Andrew Hartz <iw...@earthlink.net>
wrote:

>
>I'm looking at building an R/C boat this winter to be powered by an OS
>0.91 Surpass 4-stroke. I realize this is an air group, but I'm hoping
>someone here can help me brainstorm a little bit about how to keep the
>engine cool without propwash.
>

>Obviously, the best choice would be to use a water cooled head like the
>purpose-built marine engines use. I am, however, hesitant to chuck a
>$200+ engine in an end mill and start hacking. I had originally planned
>on using a clamp on water cooler much like is sold for Cox .049's, but
>I'm having a hard time figuring out how to do it and stay out of the way
>of the intake, exhaust, and pushrods.
>
>The engine's head will be fully exposed in the hull and will get a LOT
>of airflow as it runs around the lake, but I'm not sure that it'll get
>enough cooling, even at 40-50mph.
>
>Any ideas?
>
>Andy
>http://wwh.net/iwrc/
>

--
Dean
ri...@tc.umn.edu

[Rcsls]

os made some water cooled 60's if you look in an old engine box and find the
list of engines you will see how they did it. steve

[RickW92910]

I just sold (2) os fs 61 marines(never used) sorry,but what you can do is take
a starting belt ,very small one,run it off the grove in the fly wheel to a
shaft,pully one end and a small prop 3x6 on the other, you can run the shaft
under ,over,or just experiment with it .It works been there done that,also you
can gear up that 4 stroke for high rpm.good luck.(if you do a wet exhaust it
helps keep the engine cool also) good luck