Speediatrician
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| posted on 14/1/18 at 07:06 PM |
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Crossflow pistons: Cast vs Forged?
Do any Locost racers (with crossflow engines) use forged pistons?
If using Cast pistons, are these OK or do they crack etc. in time? How long before problems occur?
What sort of rev limit (and power) do you have?
[Edited on 14/1/18 by Speediatrician]
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redturner
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| posted on 15/1/18 at 07:41 PM |
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Never had a cast piston crack on me yet. 1000s of Formula Ford use a standard cast piston without trouble as do the 1300 Locost competition
engines.....
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Speediatrician
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| posted on 20/1/18 at 03:37 PM |
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What do the Crossflow racers rev their engines to?
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redturner
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| posted on 20/1/18 at 04:08 PM |
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A good, well put together 1600 x-flow in a Formula Ford should rev to 6900...These will be all standard Ford 1600 parts except a lightened flywheel is
allowed...
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steve m
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| posted on 20/1/18 at 05:43 PM |
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I thought the race series were standard 1300 xflows, however if im wrong, sorry !!
My xflow regularly goes to 7300 ish, but I have bent push rods, so its not ideal
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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redturner
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| posted on 20/1/18 at 06:21 PM |
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The Locost race series is 1300, I was referring to FF 1600...
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Trollyjack
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| posted on 20/1/18 at 11:04 PM |
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The Locost Series uses Std Pistons + 0.090
We are not allowed Forged Pistons
They rev up to just over 7000
TrollyJack
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Dick
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| posted on 21/1/18 at 10:38 AM |
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Turn the pistons round
Some of the race cross flow builders would fit 1300 pistons remachine the valve cut outs to allow the piston to be fitted the other way round to how
fords designed them . This shifted the tdc offset that for engineers had done these things then screamed. Never done it my self
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Speediatrician
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| posted on 27/1/18 at 07:41 PM |
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quote:
Originally posted by Trollyjack
The Locost Series uses Std Pistons + 0.090
We are not allowed Forged Pistons
They rev up to just over 7000
Thanks -how often do engines in this series need to be rebuilt?
They are about 90bhp at flywheel arent they?
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daviep
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| posted on 27/1/18 at 11:58 PM |
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quote:
Originally posted by Dick
Turn the pistons round
Some of the race cross flow builders would fit 1300 pistons remachine the valve cut outs to allow the piston to be fitted the other way round to how
fords designed them . This shifted the tdc offset that for engineers had done these things then screamed. Never done it my self
What is "tdc offset"? it is a term I'm not familiar with.
Thanks
Davie
“A truly great library contains something in it to offend everyone.”
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snapper
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| posted on 28/1/18 at 08:44 AM |
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I think there is a confusion between wrist pin offset and bore/crank offset here, wrist pin offset is to prevent the Conrad being straight up (or
down) at TDC (or BDC) this offset reduces the hard stop at both ends of the piston travel as the rod will effectively arc at TDC/BDC whilst the piston
is briefly stationary.
Bore/crank offset works in a slightly different way by providing a direct vertical thrust from TDC down the bore on the compression stroke reducing
sideways friction in the bore, bike engines like the ZX10 do this, you would think that the rod angle on the up stroke would be higher as a result.
Swapping pistons the other way round may just center the wrist pin relative to the crank or reverse the angle completely the other way, perhaps it
does make the rod angle zero on the power stroke but I would want to be very sure.
If you offset bore the crank main journals you may be able to achieve the vertical rod angle but would need to look at pin offset in the calculations.
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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