Rotax 503 racing class in the UK

[tonybroad]

picking up on a previous thread mentioning the Rotax 503 class being
introduced in the UK - it has proven to be a great success and in just
2 years there seem to be more 503's than anything

they currently race in with the F2's but score points seperately,
basically the regs are Rotax 503 engine twin carb with stock exhaust
and single fan

if anyone has 503 engines for sale i reckon theres a waiting audience
in the UK - (i dont want one though)

tony

[Frank Damp]

For someone watching this hobby from a distance who is not au fait
with the terminology, would someone please describe a Rotax 503. My
impression is that it's a 2-stroke opposed twin of 503cc displacement.
However, given the US/Europe split in definitions, it could easily be
50.3 cubic inches (about 800 cc) and might be a flat four.


Frank Damp

[Ken Roberts]

frank,

a 503 is a fan cooled twin two stroke, 500 ccs. both cylinders point the same
direction: normally, you have both spark plugs on top.

i understand they deliver about 45 hp or so. that will probably change a bit
depending on what carburetors, exhaust, etc.

this is a fairly common engine. i would think it would be easy to get parts
for.

rotax nomenclature lists the displacement ("50" means "500 ccs, or more like
499") and then a final digit that tells what equipment is on it. that would be
the "3".

for example, i have a 583 rotax. it's 580 ccs, liquid cooled and delivers about
98 hp. there's another engine called a 582 which is the same block, twin spark,
different everything that is used on ultralight aircrafts that puts out 66 hp.

Post by Frank Damp
For someone watching this hobby from a distance who is not au fait
with the terminology, would someone please describe a Rotax 503. My
impression is that it's a 2-stroke opposed twin of 503cc displacement.
However, given the US/Europe split in definitions, it could easily be
50.3 cubic inches (about 800 cc) and might be a flat four.
Frank Damp

[Ralph DuBose]

Post by Frank Damp
For someone watching this hobby from a distance who is not au fait
with the terminology, would someone please describe a Rotax 503. My
impression is that it's a 2-stroke opposed twin of 503cc displacement.
However, given the US/Europe split in definitions, it could easily be
50.3 cubic inches (about 800 cc) and might be a flat four.
Frank Damp

A 503 Rotax is a comparatively old design of aircooled 2 stroke
engine most often found in ultralight aircraft. It is also one of the
simplest, most reliable, most easily repaired 2 strokes ever built.
From a transoceanoic distance, I can see other advantages for
choosing it as the the basis for a class of competition.
1. The 45-50 or so hp it makes is enough to make competition a matter
of driving skill rather than just craft performance and also to
minimize the effect of differencies in pilot weight (compared, say, to
what is often seen in the mower engine classes).
2. The engines are going to have pretty much the same output because
they cannot really be trick-tuned without making visible changes to
the exhaust. Plus, they are piston ported, iron sleaved, and air
cooled. One can notice that engines like that all seem to have about
the same max. specific outputs.
Many good reasons exist for competitors to focus entirely on craft
design and piloting technique.

[virgin]

my good friend has just been out and bought one before xmas and has had 4
hours or so running with it - all prebuilt with some mods on engine and fan
I had a go this weekend for my sins on a day with changeable winds - on a
beach local to us- and it goes like !@xcx they are very light - this is a
single seater purchased for around 6.5k and almost ready to roll.

and for those of you out there who are new to this like us - remember to
have your engine cut offs intact - it chucked me and my mate out as we were
coming back from an ever incoming tide. yes thats two large buddies in the
same craft - single seater - sore bums and all - my mate has a bruise to his
chest where he landed on his mobile phone in one of thoses fancy plastic
coverall things. I would say in its current trim it will do about 35mph
single seater and 30 heading back with two of us - you all seem techy here
and knowledgable - any ideas on covering up the rotax filters which are
expensive- 64 pounds sterling and after only 4 to 6 hours running they are
ready with replacement - he tried a similar affair to that of a tractor air
intake wherby all the crap is collected via an intake which passes over
all - it struck up well but because it was enclosed it dies when you rev the
engine. any help on this would be appreciated as at the moment locally we
only have the beach to partake in this activity.

thansk john

Post by Ralph DuBose

Post by Frank Damp
For someone watching this hobby from a distance who is not au fait
with the terminology, would someone please describe a Rotax 503. My
impression is that it's a 2-stroke opposed twin of 503cc displacement.
However, given the US/Europe split in definitions, it could easily be
50.3 cubic inches (about 800 cc) and might be a flat four.
Frank Damp

A 503 Rotax is a comparatively old design of aircooled 2 stroke
engine most often found in ultralight aircraft. It is also one of the
simplest, most reliable, most easily repaired 2 strokes ever built.
From a transoceanoic distance, I can see other advantages for
choosing it as the the basis for a class of competition.
1. The 45-50 or so hp it makes is enough to make competition a matter
of driving skill rather than just craft performance and also to
minimize the effect of differencies in pilot weight (compared, say, to
what is often seen in the mower engine classes).
2. The engines are going to have pretty much the same output because
they cannot really be trick-tuned without making visible changes to
the exhaust. Plus, they are piston ported, iron sleaved, and air
cooled. One can notice that engines like that all seem to have about
the same max. specific outputs.
Many good reasons exist for competitors to focus entirely on craft
design and piloting technique.