Oddball engines and prototypes

[Pursang]

with insufficient blowdown (could already happen if you rev it a bit higher than intended)

Could this be taken as another indication that, with the oversquare bore/stroke, Ex timing needs to be a bit higher than normal and the Ex auxiliaries need be as large as physically possible?

Transfer blocking at over-rev seems a better option than bearing seizing or con-rod chucking!!

As far as a rev limit, that still comes down to producing a really solid 20HP at the rear wheel.
Not just a flash peak reading, it will need to maintain it for around a minute, and cover any progressive losses, due to heat loading, etc.

The Victa has no gearbox, I will be running it through a six speed Kawasaki (KMX125) with the crank replaced with a jackshaft, so some losses there.
And the option (if necessary) of a CVT or centrifugal clutch in between , with more losses.

Up to date, any modifications and (usually) improvements to my projects have been based on empirical methods and information.
This is a new and interesting exercise.

Cheers, Daryl.

[Grumph]

Daryl, is someone over there casting sunburst heads for the Victa's ?
How can I get an unmachined one ?
Thanks

Greg

[Pursang]

Hi Greg,

No new heads that I know of. Most of the stuff online is restoration of gear from the early days of karting in the sixties.
Modified Victa's also had a burst of attention in the very early days of mini-bike racing.

The head on the square case motor looks very tough. My picture is a poorly paint-shopped Maico head.

I haven't found one to measure yet but the early TS185 V-fin head looks like it might be adaptable to the 160 engine.


A fair bit of work required to create a modern squish chamber.
Don't know how well they weld either, some early Suzuki stuff is more like zinc pot metal than real Aluminium.

'Lost foam' casting looks ideal for the creation of custom, one-off, air cooled heads.

Cheers, Daryl

[Pursang]

Here's a substantial Head.



And I can't find where this is from, but someone has made a nice wooden pattern for a Bultaco styled one with plenty of meat at the base of the fins.



Cheers, Daryl.

[husaberg]

Daryl, is someone over there casting sunburst heads for the Victa's ?
How can I get an unmachined one ?
Thanks

Greg

RESUME MARK MANSELL
Mobile: 0406 043 953
Tel: (02) 96059562 (h)
Email:mmansell@bigpond.net.au

he did this one. plus hes on your island Daryl


Its even mentioned on his resume
file:///C:/Users/Glenn_2/AppData/Local/Packages/Microsoft.MicrosoftEdge_8wekyb3d8bbwe/TempState/Downloads/14_resume_12_Mark%20Mansell.%2026-3-2011%20-%20Copy.pdf

[guyhockley]

Never seen a Victa, but it sounds quite like you're heading in the same direction as many Bantam racers in the UK.

[guyhockley]

http://www.bsabantamracing.com/
The forum has loads of stuff as well as the tuning guides and articles, but attention seems to have shifted somewhat to
https://m.facebook.com/groups/222754...der&view=group
Googling Bantam racing will bring up some more sites.

[Pursang]

Trying to determine a suitable peak rpm to meet the 20 rwhp goal.
25 at crank should cover transmission losses.

Using BMEP = HP * 6500 / Cap(L)*rpm

25 * 6500 / 0.163*7000 = 145psi (10 bar)

That might be a bit optimistic, the best of the air cooled moto-crossers were apparently lucky to get to 120
(the RM125C was 123psi at peak torque and 120 at peak hp 21.7 @ 9500 )

I'll have a better pipe design, exhaust port and transfer directions than that & maybe the squish and ignition control, but the rest leaves a bit to be desired.
(60 litres per minute of coolant for example, but then the RM didn't have that either.)

For 25hp at 10,000 rpm the BMEP = 99.7 psi (6.87 bar) which seems more achievable. (the pressure if not the revs).

What have I not considered?
(Besides the practicality of even considering it)

cheers, Daryl

[Frits Overmars]

I'll have a better pipe design, exhaust port and transfer directions than that & maybe the squish and ignition control, but the rest leaves a bit to be desired
(60 litres per minute of coolant for example.)

Does that mean that you have seen the light and are switching to watercooling Daryl? In that case the good news is that you don't need 60 litres per minute;
the rule of thumb is one litre per crankshaft-HP per minute.
The bad news is that good transfer directions alone are not enough. If you are going to feed those transfer ports through tubing, as you were threatening to do the other day, chances are that the mixture columns in those ducts will be quite long and therefore quite reluctant to start flowing. So even if there is sufficient angle.area, you won't get much gass flow through all those ports, except at low revs. But at low revs you don't need the extra ports ....

[Pursang]

Does that mean that you have seen the light and are switching to watercooling Daryl? In that case the good news is that you don't need 60 litres per minute;
the rule of thumb is one litre per crankshaft-HP per minute.
The bad news is that good transfer directions alone are not enough. If you are going to feed those transfer ports through tubing, as you were threatening to do the other day, chances are that the mixture columns in those ducts will be quite long and therefore quite reluctant to start flowing. So even if there is sufficient angle.area, you won't get much gass flow through all those ports, except at low revs. But at low revs you don't need the extra ports ....

If it's water-cooled it's no longer a vintage mower / go-kart / mini-bike engine . (I might get away with a water-cooled head)
I could use any 175 cc engine, I've got a nice KDX sitting in the shed, but there's nothing very memorable about that.

Back to Cooling, ultimately the're all air-cooled, the water is just a heat transfer medium.
But I believe I need 3300 X the amount of water to absorb the heat, so 82500 litres of air/min.
I haven't found a figure for the flow restriction of a radiator, but say 50%. and assume its heat transfer ability is 100%.
Now I need 165 m3/min. or 2.75 m3/s. In my application, I'd need a radiator around 500mm2 and another 3hp.

Another interesting option would be to duct that mass flow of air over the engine, add the 50% (25 hp) of 'wasted heat', then nozzle it out the back, and generate 40lb of thrust. Add to that, the wasted heat out through the exhaust, say another 10lb and now I've got 50lb of thrust. (222 newtons)
If the bike weighs 500lb (186kg, with me aboard Ok maybe 200) I can accelerate at 1.2 m/s and reach target velocity in around a minute.
No! actually I've still got the engine power as well, so 50hp equivalent. Target velocity in 25 secs, Terminal velocity in 39. That's the Right Stuff!

Regarding the tubing ducts, (I'm sure I was just postulating & never, ever threatening), I remember Jan wishing that the internal radii could be Much Larger than was available in the RSA cylinders. Problem solved. Plus, I'll have a cooler charge because they are insulated and not in contact with the cylinder walls. ( Try some silicon oven mitts, they're great.)

If the tubing ducts are reluctant to start flowing, once they are flowing they should also be reluctant to stop?? Couldn't that increase the pressure at the port and the initial transfer flow acceleration at Tr opening?

Might need to adjust the diameters to achieve harmony at peak rev. I could put cable-ties around the hoses and adjust them progressively.

My Brain Hurts,

cheers, Daryl.

[Flettner]

If it's water-cooled it's no longer a vintage mower / go-kart / mini-bike engine . (I might get away with a water-cooled head)
I could use any 175 cc engine, I've got a nice KDX sitting in the shed, but there's nothing very memorable about that.

Back to Cooling, ultimately the're all air-cooled, the water is just a heat transfer medium.
But I believe I need 3300 X the amount of water to absorb the heat, so 82500 litres of air/min.
I haven't found a figure for the flow restriction of a radiator, but say 50%. and assume its heat transfer ability is 100%.
Now I need 165 m3/min. or 2.75 m3/s. In my application, I'd need a radiator around 500mm2 and another 3hp.

Another interesting option would be to duct that mass flow of air over the engine, add the 50% (25 hp) of 'wasted heat', then nozzle it out the back, and generate 40lb of thrust. Add to that, the wasted heat out through the exhaust, say another 10lb and now I've got 50lb of thrust. (222 newtons)
If the bike weighs 500lb (186kg, with me aboard Ok maybe 200) I can accelerate at 1.2 m/s and reach target velocity in around a minute.
No! actually I've still got the engine power as well, so 50hp equivalent. Target velocity in 25 secs, Terminal velocity in 39. That's the Right Stuff!

Regarding the tubing ducts, (I'm sure I was just postulating & never, ever threatening), I remember Jan wishing that the internal radii could be Much Larger than was available in the RSA cylinders. Problem solved. Plus, I'll have a cooler charge because they are insulated and not in contact with the cylinder walls. ( Try some silicon oven mitts, they're great.)

If the tubing ducts are reluctant to start flowing, once they are flowing they should also be reluctant to stop?? Couldn't that increase the pressure at the port and the initial transfer flow acceleration at Tr opening?

Might need to adjust the diameters to achieve harmony at peak rev. I could put cable-ties around the hoses and adjust them progressively.

My Brain Hurts,

cheers, Daryl.

Interesting, I did consider making the bottom half of a cylinder from silicon, with cavities in behind the transfers, so oil could be pumped in so as to squeeze off the transfers area. For low speed and high speed.
Never happened though.

[Frits Overmars]

Regarding the tubing ducts, I remember Jan wishing that the internal radii could be Much Larger than was available in the RSA cylinders. Problem solved. Plus, I'll have a cooler charge because they are insulated and not in contact with the cylinder walls. ( Try some silicon oven mitts, they're great.)

Jan said, as do I, that the internal radii in the transfer ducts should be as large as possible. In the RSA cylinders the available duct length was used to the max.
Lengthening the transfer ducts any further which would have nullified the effect of the larger radii.

If the tubing ducts are reluctant to start flowing, once they are flowing they should also be reluctant to stop?? Couldn't that increase the pressure at the port and the initial transfer flow acceleration at Tr opening?

Yes, the transfer flow would also be reluctant to stop, but the piston would not give a damn and slam the transfer ports shut regardlessly. That would create a pressure rise in the transfer ducts, but that pressure rise would not wait around till the next transfer opening; it would spread over the crankcase volume. So no compensation for the reluctant initial mass flow into the cylinder and on top of this a higher crankcase pressure after transfer closing, which would hurt the next induction phase.

Re the silicon oven mitts: they don't come in engine sizes, but you might use this thermal insulation paint, developed for the Russian space program and liberated by my friend Martijn Stehouwer of Emot Racing (www.emot.nl). Martijn became twice European classic 50 cc champion using the stuff.

I did consider making the bottom half of a cylinder from silicon, with cavities in behind the transfers, so oil could be pumped in so as to squeeze off the transfers area. For low speed and high speed. Never happened though.

Remember the hinged 'comma' roofs in the transfer ducts that we discussed two years ago? That didn't happen either as you came up with your sliding cylinder solution whilst I got stuck with the problem of how to operate those commas. Now I think that rubber bladders could have been a solution. Keep thinking outside the box Neil .

[ken seeber]

Daryl, in one of my early posts to KB (but it seems to be missing) there was some discussion on cooling, I mentioned and experience when I was at Orbital baselining an aircooled PE400 engine. Basically it got hot under steady state power testing causing the power to fall, irrespective of lots of practical forced air cooling. So then we set up a small micro irrigation spray to wet the cylinder and the power just rose. So, that gave rise to a couple of thoughts:

1. Dribble water over the engine
2. Arrange a small leak of fuel from the carb so it ran all over the cylinder (if you are carb forward)
3. Arrange a hose between your good self and allow this to discharge in front of the cylinder. Drink lots of water and have lots of diuretics before you go out.

[Pursang]

Interesting, I did consider making the bottom half of a cylinder from silicon, with cavities in behind the transfers, so oil could be pumped in so as to squeeze off the transfers area. For low speed and high speed. Never happened though.

That's a really good idea, I was going to have a hard time loosening off the cable ties when I got up to speed.

Jan said, as do I, that the internal radii in the transfer ducts should be as large as possible. In the RSA cylinders the available duct length was used to the max. Lengthening the transfer ducts any further which would have nullified the effect of the larger radii.

The inner radius in my B transfer is close to infinity (y axis). Horizontally, it's half the bore!

Yes, the transfer flow would also be reluctant to stop, but the piston would not give a damn and slam the transfer ports shut regardlessly. That would create a pressure rise in the transfer ducts, but that pressure rise would not wait around till the next transfer opening; it would spread over the crankcase volume. So no compensation for the reluctant initial mass flow into the cylinder and on top of this a higher crankcase pressure after transfer closing, which would hurt the next induction phase.

Fair enough...How about a couple of chambers, mounted off each side of the cylinder at transfer height, short direct ducts to the A, C & D ports. Each chamber has a reed valve fed by a large (enough) passage from the case through holes cut into the bottom of the main B transfer duct. Piston ported to the case and the B transfer, reed valved to the rest

Re the silicon oven mitts: they don't come in engine sizes, but you might use this thermal insulation paint, developed for the Russian space program and liberated by my friend Martijn Stehouwer of Emot Racing (www.emot.nl). Martijn became twice European classic 50 cc champion using the stuff.


Martijn's Site looks great, some really nice gear. Looks like he's not selling the Russian Rocket paint. Pity 'cos it would be perfect for my Ram Jet cooling & propulsion system.
The only flaw with that system is we don't get the thrust until we're already travelling pretty quickly. Needs some fans and stuff to complicate it.
Here's a link to a interesting analysis of an 'oddballish' engine. A Two stroke, compound, uniflow helicopter engine that's as light and powerful and 31% more fuel efficient than the standard turbo jet. http://dtic.mil/dtic/tr/fulltext/u2/a180007.pdf Another great idea that never got off the ground. A cynic might think that Rolls-Royce and Honeywell could probably afford more Generals & Senators than the Garrett Turbo coy.

Remember the hinged 'comma' roofs in the transfer ducts that we discussed two years ago? That didn't happen either as you came up with your sliding cylinder solution whilst I got stuck with the problem of how to operate those commas. Now I think that rubber bladders could have been a solution. Keep thinking outside the box Neil .

Daryl, in one of my early posts to KB (but it seems to be missing) there was some discussion on cooling, I mentioned and experience when I was at Orbital baselining an aircooled PE400 engine. Basically it got hot under steady state power testing causing the power to fall, irrespective of lots of practical forced air cooling. So then we set up a small micro irrigation spray to wet the cylinder and the power just rose. So, that gave rise to a couple of thoughts:

1. Dribble water over the engine
2. Arrange a small leak of fuel from the carb so it ran all over the cylinder (if you are carb forward)
3. Arrange a hose between your good self and allow this to discharge in front of the cylinder. Drink lots of water and have lots of diuretics before you go out.

I think we should keep the Piss & Dribble for discussion on how to fuel this thing.

re:#2 I have a preference for Amals, so that ones a given.

Version PE400 3.1 - A mist spray into the airsteam. I proposed this early on, when Frits first raised the Temperature Dragons ugly head.

I did some basic googly research on this and the results were mixed. Most of it is HVAC related & not relatively high velocity airstreams
Enthalpy differences between dry & humid air - the humid air already has more heat energy than dry, for example.
It takes more energy to raise the temperature of moist air than dry, blah blah.
Actually I think that is the solution. Heating the moist air takes more energy. (From the engine and then the airflow carries it away).

If I really had to, I could carry say, 20 litres of water to spray at the engine. (does one litre of ambient temp water mist cooling = 3 or 4 of hot recirculated water??)
and then perhaps I could spray some on the pipe, on gear changes, to lower the frequency and fill in the acceleration gaps caused by the extra weight

cheers, Daryl.

[Pursang]

Interesting, I did consider making the bottom half of a cylinder from silicon, with cavities in behind the transfers, so oil could be pumped in so as to squeeze off the transfers area. For low speed and high speed. Never happened though.

That's a really good idea, I was going to have a hard time loosening off the cable ties when I got up to speed.

Jan said, as do I, that the internal radii in the transfer ducts should be as large as possible. In the RSA cylinders the available duct length was used to the max. Lengthening the transfer ducts any further which would have nullified the effect of the larger radii.

Yes, the transfer flow would also be reluctant to stop, but the piston would not give a damn and slam the transfer ports shut regardlessly. That would create a pressure rise in the transfer ducts, but that pressure rise would not wait around till the next transfer opening; it would spread over the crankcase volume. So no compensation for the reluctant initial mass flow into the cylinder and on top of this a higher crankcase pressure after transfer closing, which would hurt the next induction phase.

Fair enough...How about a couple of chambers, mounted off each side of the cylinder at transfer height, short direct ducts to the A, C & D ports. Each chamber has a reed valve fed by a large (enough) passage from the case through holes cut into the bottom of the main B transfer duct. Piston ported to the case and the B transfer, reed valved to the rest

Re the silicon oven mitts: they don't come in engine sizes, but you might use this thermal insulation paint, developed for the Russian space program and liberated by my friend Martijn Stehouwer of Emot Racing (www.emot.nl). Martijn became twice European classic 50 cc champion using the stuff.


Martijn's Site looks great, some really nice gear. Looks like he's not selling the Russian Rocket paint. Pity 'cos it would be perfect for my Ram Jet cooling & propulsion system.
The only flaw with that system is we don't get the thrust until we're already travelling pretty quickly. Needs some fans and stuff to complicate it.
Here's a link to a interesting analysis of an 'oddballish' engine. A Two stroke, compound, uniflow helicopter engine that's as light and powerful and 31% more fuel efficient than the standard turbo jet. http://dtic.mil/dtic/tr/fulltext/u2/a180007.pdf

Remember the hinged 'comma' roofs in the transfer ducts that we discussed two years ago? That didn't happen either as you came up with your sliding cylinder solution whilst I got stuck with the problem of how to operate those commas. Now I think that rubber bladders could have been a solution. Keep thinking outside the box Neil .

Daryl, in one of my early posts to KB (but it seems to be missing) there was some discussion on cooling, I mentioned and experience when I was at Orbital baselining an aircooled PE400 engine. Basically it got hot under steady state power testing causing the power to fall, irrespective of lots of practical forced air cooling. So then we set up a small micro irrigation spray to wet the cylinder and the power just rose. So, that gave rise to a couple of thoughts:

1. Dribble water over the engine
2. Arrange a small leak of fuel from the carb so it ran all over the cylinder (if you are carb forward)
3. Arrange a hose between your good self and allow this to discharge in front of the cylinder. Drink lots of water and have lots of diuretics before you go out.

I think we should keep the Piss & Dribble for discussion on how to fuel this thing.


Version PE400 3.1 - A mist spray into the airsteam. I proposed this early on, when Frits first raised the Temperature Dragons ugly head.

I did some basic googly research on this and the results were mixed. Most of it is HVAC related & not relatively high velocity airstreams
Enthalpy differences between dry & humid air - the humid air already has more heat energy than dry, for example.
It takes more energy to raise the temperature of moist air than dry, blah blah.
Actually I think that is the solution. Heating the moist air takes more energy. (From the engine and then the airflow carries it away).

If I really had to, I could carry say, 20 litres of water to spray at the engine. (does one litre of ambient temp water mist cooling = 3 or 4 of hot recirculated water??)
and then perhaps I could spray some on the pipe, on gear changes, to lower the frequency and fill in the acceleration gaps caused by the extra weight

cheers, Daryl.