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Author Topic: Twin Engine Panther from England  (Read 57404 times)
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wobblywalrus
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« Reply #210 on: April 02, 2012, 10:28:50 PM »

That is great, Sumo.  Nice job.
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Koncretekid
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« Reply #211 on: April 03, 2012, 09:42:15 AM »

Sounds good, Sumo. It even idles.  And it doesn't seem to be jumping up and down..............yet! Let us know if it remains smooth (relatively, anyway) at higher RPM's.
Tom
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We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!
SUMO
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« Reply #212 on: April 03, 2012, 11:25:32 AM »

Sounds good, Sumo. It even idles.  And it doesn't seem to be jumping up and down..............yet! Let us know if it remains smooth (relatively, anyway) at higher RPM's.
Tom

yea idles about 600rpm when warm (stock sits about 450 haha) it's pretty smooth. even at road speeds, not had it above about 35mph yet, but seems more spritely than a stock one so we shall see what it pulls in top after its all run in grin so far so good
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SUMO
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« Reply #213 on: April 10, 2012, 03:45:03 AM »

made up a breather for the race motor at the weekend. [the ugly black tube to the left of the pushrod tube] every little bit helps. i think i will make a bigger breather for it in the long run but this is a start

it has a couple hundred miles on it now and it seems a much more streetable motor now. i guess in a week or so ill see what we have extra in the way of top end... [probably on the way over to the Low Level Hell do over in a welsh direction - should be a good leg stretch for it - seems to be running and starting well so fingers crossed]

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panic
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« Reply #214 on: April 10, 2012, 08:15:59 AM »

Sorry if I overlooked this, but what sort of breather do these have?
Timed disc, flap, rotor?
Typically, a 1 cylinder has the worst problems unless the case volume is big.
Is there any large fitting on the case you can borrow for another purpose (timing hole, inspection etc.)?
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SUMO
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« Reply #215 on: April 10, 2012, 08:27:00 AM »

breather on these is a tiny bore down the crank with a nut on the end with a metal disk in it / split pin over it to create sort of a butterfly system. the case volume is pretty big with the inbuilt oil boot

the hole i have used on the timing side is access to the oil feed adjustment - its about an inch dia - this is what i intend using, i put an 8mm breather because thats as big as i could without too much machining effort, but will make up a full diameter one when i get a chance
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panic
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« Reply #216 on: April 10, 2012, 08:30:55 AM »

How are the cranks phased:
1. simultaneous power strokes
2. 360 separation
3. 180/540 separation
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SUMO
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« Reply #217 on: April 10, 2012, 08:42:21 AM »

on the twin engine i dont know yet - best plan seems to be simultaneous power strokes speaking to people that have built twin engine bikes - seems they stay in one piece better that way
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panic
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« Reply #218 on: April 10, 2012, 08:51:18 AM »

From what I've read that's true - the coupling doesn't like load reversals.
However: it means you can't use the other case volume as a buffer.
Have you tried putting a gauge on the breather with the engine running so guess at max pressure?
You can increase the volume of both with a sealed can connected to each with a large hose/pipe. A 3" ID 12" tube is 74" volume.
Another possible is a reed controlling the only vent, so the case pumps itself down to a minimum level after a few seconds
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SUMO
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« Reply #219 on: April 10, 2012, 09:00:17 AM »

not yet i havent no - its on the endless list though

From what I've read that's true - the coupling doesn't like load reversals.
However: it means you can't use the other case volume as a buffer.
Have you tried putting a gauge on the breather with the engine running so guess at max pressure?
You can increase the volume of both with a sealed can connected to each with a large hose/pipe. A 3" ID 12" tube is 74" volume.
Another possible is a reed controlling the only vent, so the case pumps itself down to a minimum level after a few seconds
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panic
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« Reply #220 on: April 10, 2012, 09:38:21 AM »

I'm not sure what level of positive pressure is acceptable before you get oiling past the guides and rings.
The only way IKO to get vacuum in the case without a timed breather is a reed. Krank Vent is $$, take-off from big motorcycle needs some adapting but cheap.
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Queeziryder
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« Reply #221 on: April 10, 2012, 12:04:55 PM »

Sumo
Look up Ducati crank breathers, we use them a lot on heavy breathing Vincents, and they seem to work well.
You would need to make an adapter to screw the Duke valve into, but its internal bore would work well with your 1" dia point on the Panther cases.

Neil

PS
Find them on eBlag for less than 35 on a regular basis
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panic
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« Reply #222 on: April 10, 2012, 01:07:29 PM »

Is this it?
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panic
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« Reply #223 on: April 10, 2012, 01:55:42 PM »

I was somewhat surprised at the remarks on use (and mod) of this valve on the Ducati.
The trend appeared to be re-locating the valve to the end of a large container (air box) to add plenum volume.
I think this is a mixed message, and not sound practice.
The 2 operations work in opposite directions (albeit toward the same purpose: reduced pumping loss).

Adding a plenum simply buffers whatever pressure cycling occurs during crank rotation, but the case volume change (slightly less than the engine displacement) transfers back & forth through the connecting hose every TDC continuously. If the passage is small enough to be a restriction (like 1/2" ID hose), the gain decays to merely cosmetic. Pushing 900cc through a 1" hose is easy to calculate, it's piston speed (piston^2 1^2). Let's assume 60 f/s for the piston, and 104mm (about 4.09") for the bore. That makes the speed in the 1" hose 1,000 f/s.

A valve should be as close to the case volume as possible so that (beginning with start) the volume expelled does not return, and each successive cycle reduces the mass of vapor in the case until a slight vacuum is constant (there is always some expansion due to ring leakage and heat soak). This means that the valve's capacity is not relevant except for the first few seconds.
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panic
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« Reply #224 on: April 10, 2012, 02:50:56 PM »

From a few e-mails, it appears I left a thread hanging.
The displaced case volume is of course the engine displacement in a single, or 360 parallel twin, and half the displacement in a 180 twin, etc. (which still has some pumping, but it's between the cylinder mouths below the deck).
A V-twin always has somewhat less than 100% case volume expulsion because the 2 cylinders don't reach BDC together, so the volume displaced is the full piston area the stroke length at 1/2 of the V angle: 22.5 BBDC for H-D, 45 for Ducati, etc. The exact figure of course depends on the rod ratio.
For a 80" OHV twin (4.25" with 7.4375" rod) the effective stroke at 157.5 ATDC is 4.133" giving about 97% of engine size as volume change.
« Last Edit: April 10, 2012, 02:52:40 PM by panic » Logged
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