Oddball engines and prototypes

[Frits Overmars]

Attachment 331750
Now I want to look at a couple of other older engines in the stable.

In case you want to extract the angle.area values from those older engines: don't; it will blurr your view.
Here is something a little less vintage, that I posted on the French Pit-Lane forum: http://www.pit-lane.biz/t6246p25-gp1...vermars-part-5


PS: did Agnetha, Björn, Benny and Anni-Frid really make it to the Nobel Committee? I think I like their music after all .

[Pursang]

In case you want to extract the angle.area values from those older engines: don't; it will blurr your view.

Not to use them as examples of good practice, but to determine if additional transfer, blow-down and a FOS pipe could be usefully & practically applied.

Here is something a little less vintage, that I posted on the French Pit-Lane forum: http://www.pit-lane.biz/t6246p25-gp1...vermars-part-5


Thanks for that, I had read your words and put my interpretation into the worksheet. But I'm not a member, so couldn't see the illustration.
The effective areas are very clear, but it was probably of some value to work it out myself.
The rates of change of area, due to piston motion, are not as important as I expected. But I will pay attention to my chords.

A couple of other questions from that post:

130 transfers, no stagger. Does that mean engines that operate better with stagger probably have less than optimum port directions/dimensions?

The 'mirror' of the blow-down (the blow-back?). This is the ideal time for the pipe to push charge back into the cylinder.
Does extending the Ex duration (within reason) actually allow the pipe to be effective over a broader range of RPM & temp? (A bit contrary to accepted theory.)

PS: did Agnetha, Björn, Benny and Anni-Frid really make it to the Nobel Committee? I think I like their music after all .
No, but I bet they know some-one who is, just a couple of degrees of separation might be all you need

Cheers, Daryl.

[Frits Overmars]

130 transfers, no stagger. Does that mean engines that operate better with stagger probably have less than optimum port directions/dimensions?

I would not be so bold as to confirm your supposition unconditionally. But I like to keep things surveyable (all transfer port equally high) and I know that in the case of the Aprilia the A-transfers could not be made any higher without eating into the real estate of the auxiliary exhaust windows.
I would also recommend reading through Wobbly's views on stagger.

The 'mirror' of the blow-down (the blow-back?). This is the ideal time for the pipe to push charge back into the cylinder.
Does extending the Ex duration (within reason) actually allow the pipe to be effective over a broader range of RPM & temp? (A bit contrary to accepted theory.)

That might well the case Daryl. If there is a bigger time window between transfer closure and exhaust closure, the pipe has a broader opportunity to push charge back into the cylinder. But the exhaust timing itself cannot be raised at will. For true resonance we need an effective duration of 180° which would work out at a geometrical timing of about 190°. However, in some cases a higher exhaust timing may be needed to strike the best compromise between resonance and blowdown angle.area.

This line of thought leads to the conclusion that the transfers should not be made any higher than strictly necessary. The lower they are, the less risk of washed-through mixture and even spent gases getting pushed back into the transfer ducts and into the crankcase. 130° gives a good balance between maximizing the transfer angle.area, minimizing this risk and maximizing the time window between transfer closure and exhaust closure.
This is one more reason to avoid stagger: stagger will only partially help the transfer angle.area but the highest transfer port will determine the gravity of the above-mentioned risk.

[Pursang]

Transfer angle.area determines the effective (torque peak) rpm.

Many/most/all 'vintage' competition engines are transfer a.a deficient and make their power by multiplying the reduced torque by as many revs as possible.
Of course they are also blow-down a.a deficient as well, this is partially compensated by 'hogged out' Ex ports that can continue blowing-down into the transfer period, further reducing the effective Tr a.a. (It gets worse & worse, the more you think about it ........but just 'cos they're not perfect, doesn't mean they're not Fun )

Q: For engines limited by the available Tr a.a, (ie. below Optimum STA) should the Blow-down STA be reduced (if necessary) to match, or be as close to Optimum as possible?


Cheers, Daryl

[Pursang]

Q: For engines limited by the available Tr a.a, (ie. below Optimum STA) should the Blow-down STA be reduced (if necessary) to match, or be as close to Optimum as possible?

After re-reading, I think I might have answered my own question:

If the Tr a.a is limited, I should aim for Optimum blow-down, to minimise any transfer obstruction/delay and even, perhaps, give it a "head start" by creating negative cylinder pressure well before TPO.

I haven't seen any EngMod2T traces that look like that. They all seem to be just on, or over, the edge of pressurising the transfers.

Cheers, Daryl

[Frits Overmars]

Many/most/all 'vintage' competition engines are transfer a.a deficient and make their power by multiplying the reduced torque by as many revs as possible. Of course they are also blow-down a.a deficient as well, this is partially compensated by 'hogged out' Ex ports that can continue blowing-down into the transfer period, further reducing the effective Tr a.a.
(It gets worse & worse, the more you think about it .......

Ain't that the truth. Just keep on thinking: if the blowdown a.a does not alllow the cylinder pressure to drop below crankcase pressure by the time the transfers start opening, the exhaust gases will relentlessly abuse the transfers as auxiliary exhausts. Only when the cylinder pressure has dropped far enough, can the transfer phase begin. And what is being transferred first? The exhaust gases that filled the transfer ducts! Only after the transfer ducts have cleared their throats, can the transfer of fresh mixture begin. In short: insufficient blowdown a.a. will eat doubly into the transfer a.a.

just 'cos they're not perfect, doesn't mean they're not Fun

Ain't that true too. Internal combustion engines are hopelessly inefficient compared to electromotors (if you take the availability of electricity for granted...).
But which is more fun? Gimme combustion any time .

After re-reading, I think I might have answered my own question.

You did .

[Pursang]

Internal combustion engines are hopelessly inefficient compared to electromotors (if you take the availability of electricity for granted...).

Reliable electricity anywhere, any time, just need some petrol.

cheers, Daryl

[lohring]

[QUOTE=Frits Overmars

Ain't that true too. Internal combustion engines are hopelessly inefficient compared to electromotors (if you take the availability of electricity for granted...).
But which is more fun? Gimme combustion any time .

You did .[/QUOTE]

You can have fun with electrics as well, but it's a different game. This 2008 record we set still stands but think what you could do with a 2017 electric power plant.

Lohring Miller

[Pursang]

Hi Lohring,

That record run was impressive, especially considering the Voltage & Motor restrictions.

At least brushed motors make a pretty cool noise when they're winding up & running Flat Out!

That other stuff you do is pretty cool too!

Cheers, Daryl.

[lohring]

Most of the noise was from the quick change gears. We wanted to run proven props and they turn around 10,000 rpm on IC outboards. The brushed motor we used was limited to 5,000 rpm. Mike Bontoft designed and built a great gear box using standard quick change gears that allowed us to match the motor to the prop. We changed the gears several times before we topped out the speed at a little over 100 mph. It wasn't quite enough to get a two way run to average over 100. It took a few batteries, but they were a lot lighter than the lead acid batteries that were used previously.

Lohring Miller

[Grumph]

Very neat. Not the first time I've seen QC gears used for something odd. They can be a very handy answer to finding a source of readily available gears.

[Pursang]

No wonder I like the whine of quick change gears,
my Dad built and raced Midgets in the 50's

Cheers, Daryl

[Grumph]

No wonder I like the whine of quick change gears,
my Dad built and raced Midgets in the 50's
Cheers, Daryl

Those pics take me back. Very similar atmosphere at the time on this side of the Tasman. Push starting race cars on grass....

The Standard Vanguard engine was not used as much as it could have been for motorsport. Triumphs obviously, but special builders didn't seem to want to use it - and it was common as they were assembled here. My old man worked at the assembly plant in ChCh as a day job.
Hec Green's ChCh built twin cam alloy race engines were built around the Vanguard crank - supplied courtesy of the old man...

[WilDun]

The Standard Vanguard engine was not used as much as it could have been for motorsport. Triumphs obviously, but special builders didn't seem to want to use it - and it was common as they were assembled here. My old man worked at the assembly plant in ChCh as a day job.
Hec Green's ChCh built twin cam alloy race engines were built around the Vanguard crank - supplied courtesy of the old man...

That engine was very good and was used in just about everything from Fergie tractors to family cats to Triumph sports cars (diesel versions too - as used in the Fergie Diesel tractors and some Taxi cars in Britain - these were very successful and the sweetest running little diesels ever, however not so well known in NZ, just in the tractors at the airports, also used in Antarctica by Edmond Hillary).
I would be interested in the twin cam alloy engine too, did he use any other Vanguard parts other than the crank? (eg the wet liners).

[Grumph]

That engine was very good and was used in just about everything from Fergie tractors to family cats to Triumph sports cars (diesel versions too - as used in the Fergie Diesel tractors and some Taxi cars in Britain - these were very successful and the sweetest running little diesels ever, however not so well known in NZ, just in the tractors at the airports, also used in Antarctica by Edmond Hillary).
I would be interested in the twin cam alloy engine too, did he use any other Vanguard parts other than the crank? (eg the wet liners).

I don't know how much of Hec's work is on line Will. He was written up in a series of articles in Classic Driver mag a few years back, they may be on line. He built a series of R.A. Specials - won the second Lady Wigram trophy race in the first.
The alloy 4cyl was twin cam, 2V per cylinder, cams driven by surplus Merlin engine gearing. Hec made rods, cams and I think pistons too.
Cast in ChCh by I think the Symonds bros who got one engine for a hydro. 2 or 3 survive. A guy I know has the last RA Special tucked away. Hec didn't want it brought out at the modern classic meets for some reason. He and his business partner, Jack Brewer - who ran the Lady Wigram meeting for years - and my old man were close mates. All 3 were AMIMechE qualified and represented a think tank of no mean ability.
Actually, memory has just kicked in, Hec's first rear engined car was the RA Vanguard. Supercharged and on alky, it was quick enough that when Geoff Mardon had it, he qualified on the front row for the Dunedin street race against the internationals. Officialdom didn't believe the times and put him well back. He was going up through the field very quickly when a wheel broke...Same thing happened to Les Moore (Ronnie's father) but it killed Les that time.

Here's a pic for Daryl - just to whet your ambition....