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KR crank options?

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slindo

Posts: 66

Joined: Tue Jan 08, 2008 7:25 pm

Post Fri Jan 25, 2008 4:51 pm

Re: KR crank options?

It'll be fun to see if Panic jumps on you for saying this, the way he would jump on me if I had.

If you've been paying attention, you would realize that, in the Gospel according to Panic, flywheel weight is COMPLETELY IRRELEVANT (well, other than for calculating postage) so much so, that anyone who even is curious as to what it is must be branded a fool.

thefrenchowl wrote: For a given power/capacity, there must be an "ideal" flywheel assembly weight to make it tractable and usable, even for racers...
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panic

Post Fri Jan 25, 2008 7:46 pm

Re: KR crank options?

So, my comments are based not on the text, but the identity of the person speaking?

You couldn't be more wrong.
I disagree with everyone eventually - and they correct me when I put my foot in my mouth, because no one is right all the time. I'm certainly more diplomatic to someone making an honest mistake, once (i.e., "I think you accidentally reversed to figures"), than to someone who continues to ask questions, but rejects any response that's not the one he wanted to get.
That's not seeking information - that's trying to validate your prejudices.

But then since you STILL don't understand what I said, this must be your only method of rationalizing.

Now, your turn: repeat your original errors, using slightly different wording.
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45Brit

Posts: 1419

Joined: Tue Nov 27, 2007 2:29 am

Post Sat Jan 26, 2008 2:22 am

Re: KR crank options?

I like the description of Alan Girdler's books ... I have a couple and yes, he is a magazine journalists and it shows rather. Good read, but no real use for reference.

I suspect that the reason H-Ds use less oil on racers is indeed wet sumping, plus the short running periods. Speedway and grasstrack bikes use quite low oil flow rates, and very small volumes, because they only need to run for a few minutes, without choking on unconsumed or unexpelled returns; and I would suspect it is the same for a flat-track bike - what is the duration of a flat-track race?

slindo's posts read to me like a lot of the stuff that lands on my desk, people who have more-or-less decided what they are going to do but are worrying at it, fiddling with details, trying alternatives and rejecting them, all without quite having sufficient experience or information. Normal old-bike project behaviour!!

the torque curve for a given engine is related to a whole host of things, including rod length, flywheel weight and diameter, cam profiles etc. Flywheel weight doesn't actually act as a constraint on achievable torque, but it certainly affects HOW that torque can be applied.

personally, and this is just me, I would reckon that once the words 'complete fool' appear in a thread of this nature, then at least one party involved is getting off the subject rather....
Shoot, a man could have a good weekend in Dallas with all that stuff...
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thefrenchowl

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Post Sat Jan 26, 2008 3:15 am

Re: KR crank options?

45Brit:
I suspect that the reason H-Ds use less oil on racers is indeed wet sumping, plus the short running periods. Speedway and grasstrack bikes use quite low oil flow rates, and very small volumes, because they only need to run for a few minutes, without choking on unconsumed or unexpelled returns; and I would suspect it is the same for a flat-track bike - what is the duration of a flat-track race?


Yes, some flat track were indeed short, but they used the same setup for Daytona, more or less 200 miles flat out be it on the sands or the oval, or stuff like the 50 milers... They also had what they called non-championship "Speedway" in the 50's, up to 100 miles. They in the end went for a sump and "decent" oiling around 1975 on the XR...

The only thing I would slightly disagree with Panic is his use of the "delete" function!!! Me, if I put my foot in it, I just let it run and correct or apologize later, it's only human to make errors or being too quick on the keyboard!!!

Slindo, well, it's YOUR KR engine, I can't really help it if you're not too sure what to do with it. In the end YOU only can do something with it, but you should have more faith in some of the advise dished up freely on these pages. Some of us have learned all this stuff the hard way, before internet forum times, by trial and error. It obviously pays up if you have an analitical mind that can cut through the trivial and focus on the important.

The starting point is that all H-D racers were based on slightly modified street components, that's what Class C racing was about, hence anything std can be made to fit the specialized purpose... It's also worth knowing that H-D, if they could help it, NEVER made anything special. Their team of engineers would use, as described before, std bushes or bearings out of suppliers catalogues, so all the hardware components you'll need are out there... Get your cases on the table and start measuring!!!

Patrick
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45Brit

Posts: 1419

Joined: Tue Nov 27, 2007 2:29 am

Post Sat Jan 26, 2008 7:33 am

Re: KR crank options?

I don't actually know a great deal about the organisation of US bike sport... I've seen 'On Any Sunday' and that's about it. Likewise I've rarely been to the US, and then only for work, with one exception, and flat-track played no part at all in that.

People tend to expect someone like me, with a long spell in the offshore oil business and a lot of American knick-knacks which I have picked up along the way, to be more-or-less Americanised, and that isn't so. Europeans rarely work in the US sector, mainly because of various issues to do with visa, tax, rotations and rates of pay. Americans are rarely found in the European sector these days, because they have developed far beyond anything done in the US. Some sectors which are important in the US, particularly land rigs and shallow-water inshore drilling, are largely absent anyway. Europeans also, will not usually tolerate certain aspects of American man-management practices, if they can do something else instead. Changes in world politics tend to mean that Americans are increasingly unwelcome in some places where Europeans can work without serious difficulty.

so, I've never seen Daytona, flat-track or arena racing, and don't suppose I ever will. I don't really understand how people can race 45s on 1/8 mile tracks, which is something I've seen referred to. I've once seen a running XR, at Kings Lynn on a track session, and I've never actually seen a K series of any kind.


anyway good luck with the K project. I know about having a bundle of parts and no idea of quite how to progress. For what it's worth, I usually start by picking a course and sticking to it, except insofar as I see fit to modify it in the light of things I learn or acquire along the way. I would advise you to make a start, at which a lot of things will either become evident, or be eliminated by other decisions. I would advise you to take Patrick's advice about the Sportster crank, because (1) Patrick's bikes work well and (2) I am a great believer in a project of this sort, of starting with the biggest, most complete lump you can, and a crank would certainly qualify
Shoot, a man could have a good weekend in Dallas with all that stuff...
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MOLDTHREAD

Posts: 122

Joined: Fri May 04, 2007 5:46 am

Location: BRANFORD, CT

Post Sat Jan 26, 2008 3:00 pm

Re: KR crank options?

I’m kind of hesitant to stick my nose in here, but I would like to add my experience with crankshaft weights.
I go along with Panic that the actual weight of the flywheel is not the critical thing regarding the performance, although it is factor. He is trying to make a point by exaggerating the argument so that we all can see it.
What we should really be talking about is the MOMENT OF INERTIA of the flywheels. The mass and distance from the rotating center of the flywheels. The distance of this center of gravity from the axle is the most critical as it is the square of the distance. This is what allows the crank to accelerate and decelerate faster or slower. That’s why they add a big rim to the flyheels on machines
I had a very good illustration of this several years ago. I have been flattrack racing 500cc Enfields for about 10 years, and for the last 5 Ronnie Rall has been riding one of my bikes. When he was racing as a pro in the 70’s he was considered one of the best if not “The” best cushion track rider in the country. I got to thinking (this usually causes problems) that if I were to use lighter flywheels (less moment of inertia) it would help slow the bike down faster (no brakes) going into the corner. I tried several different cranks both about 18# as opposed to the stock 22# assemblies. The end result was a complete disaster, Ronnie didn’t like it at all, while the bike did slow down faster; the problem was getting on the gas coming out of the corner. The throttle was TOO sensitive; at the slightest bit too much throttle the rear would break loose and start to spin, making it very unpredictable and harder to ride. All other parts of the bike were identical before and after this change. I have since gone back to a heavier flywheel with approximately the same moment if inertia. I did not really consider the moment of inertia when I started this.
Bruce Argetsinger
AHRMA Dirt Track # 67J
www.enfieldracing.com
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45Brit

Posts: 1419

Joined: Tue Nov 27, 2007 2:29 am

Post Sat Jan 26, 2008 4:04 pm

Re: KR crank options?

exactly so. Moment of inertia is the critical thing. This is also why JAP swapped between longer and shorter con-rods on their 500cc speedway engines - to vary the power delivery characteristics in this fashion, because the angle between the con-rod and the direction of thrust affects the torque developed at the flywheel at that stage of the rotation. Rod/piston assembly weight also figures, as previously mentioned
Shoot, a man could have a good weekend in Dallas with all that stuff...
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thefrenchowl

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Location: Crewe, Great Britain

Post Sat Jan 26, 2008 4:05 pm

Re: KR crank options?

Bruce:
I’m kind of hesitant to stick my nose in here


Don't be, Bruce, you actually tried different set ups in real life racing so your experiences are welcome here!!!

Your comments seem to confirm the "abrupt" nature of low inertia engines... Might be OK sometimes on tarmac racing but certainly not on dirt.

By the way, do your K type regrinds have the convex lobes? I've shown my KHK cams to some people over here in GB, they could do the rough lobes but they don't have the machinery to grind them...

Patrick
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MOLDTHREAD

Posts: 122

Joined: Fri May 04, 2007 5:46 am

Location: BRANFORD, CT

Post Sat Jan 26, 2008 5:01 pm

Re: KR crank options?

Patrick,

My lobes are concave, They are CNC milled rather than ground. I make them with correct angles for STD. 45's, WR's, K's, KR's. I've just measured up KHK's. Over on this side of the pond Milled cams have been used in the WR's for quite a while with roller tappets. The only experience we have is in racing and I don't know how the would stand up for street use. I assume they would be OK becausr of the roller. I am using harder cams that are Wire cut EDM in my Enfield's with flat tappets and they seem to be fine.

45 brit,
I'm aware of what you say about long and short rods, but I haven't got that all figured out along with long and short stroke, and offset wrist pins?
To open a can of worms. Is this something that really affects performance or just new things that have been tried over the years and something for people to argue about?
Weight of rods and pistons shuld be taken into consideration in the balance factor and not dramaticly effect the moment of inertia.
It's amazing how much all these things effect each other and it's hard to tell what is important and what the effect of each one is.
Bruce Argetsinger
AHRMA Dirt Track # 67J
www.enfieldracing.com
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panic

Post Sat Jan 26, 2008 5:50 pm

Re: KR crank options?

I think the actual change in cylinder pressure vs. vacuum vs. best use of the work cycle before EVO are all changed by mods to the rod ratio (perhaps changes of +/- 10% or more?), but they're not all working in the same direction, and I don't see a clear pattern of "if A, then B".
An engine with big ports and late intake closing will (generally) pick up cylinder pressure a bit (although peak pressure may go either way) with a shorter rod (such as Branch's KR with 1" off the rod length) because the stroke remaining at the same IVC point is longer - more gas is captured, and the DCR goes up slightly. The vacuum in the critical ATDC period also goes up, which increases fill early in the cycle.
However, engines with small ports, low lift, early intake closing will get the reverse: not as much inertia fill ABDC, and restricted breathing TDC to perhaps 25 ATDC due to out-flowing the valve curtain.
Some engines have a mix of these characteristics, so results aren't really predictable except perhaps with Blair's $$$oftware.
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thefrenchowl

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Location: Crewe, Great Britain

Post Sat Jan 26, 2008 6:57 pm

Re: KR crank options?

Hi Bruce,

Obviously, any mechanical choice in any engine has some advantages and drawbacks... If there was a perfect answer, we wouldn't be discussing the matter.

Still, they are constants. if you want torque and tractability, it follows that the straighter the rod in the power stroke, the better, hence you can use offset pistons (or offset cylinders in the old days...) to good effect in a long stroke set up. But that don't work so well with short rods or stroke due to mechanical/room constraints.

If you draw an offset pin or cyl on AutoCAD, you will notice that the upwards compression/exhaust stroke diminishes in degrees while the downwards intake/power stroke lenghtens, hence the time it takes increases, weird...

And, Panic, the main drawback of the short rod/stroke is that a lot of the power is lost in side thrusts so whatever more mixture you managed to put in due to less piston wasted motion isn't used properly hence more revs to compensate!!!

Anyway, probably the best racing engines are the ones with a good set of "compromises" and might explains why some engines are infinitively tunables while others are just street lumps...

Patrick
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45Brit

Posts: 1419

Joined: Tue Nov 27, 2007 2:29 am

Post Sun Jan 27, 2008 1:01 am

Re: KR crank options?

JAP started with the 'short rod' 500cc engine in the early 1930s, then went to the 'long rod' engine two years later for mechanical reasons ( to reduce the big-end loadings ). The 'Long 4' was reckoned to be a distinct improvement in tractabilty and overall torque. The next variant of lower end geometry was the last engine in the series, the 1960s 84S, which was completely redesigned to reduce the stroke from 99mm to 84mm.
Shoot, a man could have a good weekend in Dallas with all that stuff...
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panic

Post Sun Jan 27, 2008 10:21 am

Re: KR crank options?

"the main drawback of the short rod/stroke is that a lot of the power is lost in side thrusts"

But... none of these changes occur in a vacuum.
The entire Mark Series (BBC) is based on opposing that concept: high port volume + large X-sectional area + short rods (427: 6.135" rod, 4.00" stroke = 1.53:1 ratio, 19° thrust angle) = high power.
That same engine with 1" longer rods (1.78:1, 16.3°) would have perhaps 10 HP more from reduced drag, but 30 HP less due to lazy port action. The analogous 440 RB has a better rod ratio but much smaller ports - similar (but inferior) effect, plus higher engine weight and size.
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thefrenchowl

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Post Sun Jan 27, 2008 11:49 am

Re: KR crank options?

Hi Panic, just trying to wind you up!!!

I'm in no doubt my Honda 450 CL delivers the same bhp as my 900 KHK, BUT it has to rev to 9500rpm to do that, that's a direct result of short rod/stroke, never mind 5 speeds in the gearbox and using the shift lever like a jockey uses his stick... This tells me that CL don't have a clue how to generate a modicum of torque/power in the range of the KHK, say 3000 to 5500 rpm.

Only way to make more power is rev to death and burn more mixture, that's how the short rod/stroke came about, not the reverse.

If one compares the behaviour of contemporary stuff, say a 750 KRTT and a Daytona 500 Triumph, I'm pretty sure the power was about the same, BUT the KR could pull a much taller gearing to get to 150 while the Triumph sat there at about 135, REFUSING to pull. That's the typical battle, low rev torque/long stroke vs high rev power/short stroke...

I will agree with you that in a long stroke, the piston hovers for a long time at each end of the stroke, but, it make then sense that the vaccum they generate to fill the cyl must be a lot higher than on a short stroke since it's got to accelerate faster to catch up the lost momentum at any given revs??? Could this have a favorable effect on the torque curve? Me thinks so!!!

Patrick
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Payton

Posts: 56

Joined: Fri Aug 31, 2007 8:31 am

Location: Central Fl.

Post Sun Jan 27, 2008 12:17 pm

Re: KR crank options?

Panic wrote:

such as Branch's KR with 1" off the rod length

///////////////////////////////////////////////////////////////////////////////////////////////////////////////

I am probably getting off the subject somewhat, but as I recall, the short rod motor did not perform as well as hoped for.

I think it was Gordon Jennings again with Jerry Branch who wrote an article which i am unable to find, about a KR special
with an aermachhi type frame and the short rod engine that was raced at Daytona. I know the procedure that was used for
the shortening of the rod, but I can't recall what they did to shorten the cylinder. Anyone have a clue?

The reason I ask is that I have a KR cylinder with a rather thin flange. The flange was turned down evidently to get
compression up, and except for the flange is a good cylinder. About the only way I see to shorten a cylinder is to remove
the flange and reweld it to the cylinder. I wanted to verify this is what Branch did in the article by Jennings.

Jack
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panic

Post Sun Jan 27, 2008 12:42 pm

Re: KR crank options?

Read the same thing, rods were sliced diagonally to have as much of the weld in shear as possible.
I couldn't figure out what they did with the cylinders, not only because taking it off the top is impossible (exposes the intake port) or the bottom (no flange left), so we're left with cut, insert sleeve for continuous wall surface, and weld.
However: even discounting the warping, that leave the ports practically touching. What to do about the manifold?
IIRC AMA: "zylinder speciale ist verboten", but somehow they never managed to notice the special castings for the iron-head XR750...?

I suspect it was a new casting with the area above the flange amputated and the nipples moved back into the ports, and Branch (being ex-officio factory) was sworn to secrecy.
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Payton

Posts: 56

Joined: Fri Aug 31, 2007 8:31 am

Location: Central Fl.

Post Sun Jan 27, 2008 1:01 pm

Re: KR crank options?

All you can do is try. If it works, fine, if not, fine.
Last edited by Payton on Wed Jan 30, 2008 10:00 am, edited 1 time in total.
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thefrenchowl

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Post Sun Jan 27, 2008 2:28 pm

Re: KR crank options?

Payton,

These KR short rods cylinders were even shorter than you might think, they had to have a vertical magneto as the front of the timing cover was deleted to clear the front exhaust stub!!! There's a good photo of the 1967 Aer-Macchi framed short rod KRTT in Stephen Wright American Racer 1940/80. It only managed 16th place during qualifying at 129.72mph, against Fred Nix's 1st post at 140,82mph

What you have are most probably KH/KHR cylinders that have been shortened for use on a K/KR... I've seen it done a few times, I even have a KH pair like that!!!

Panic,

the AMA said you had to use listed/submitted KR cylinders or parts, it said nothing about moding/welding/porting std KR cylinders or parts!!! Same for the atrocious Waffle Iron XR heads fitted with twin carbs and blanked/redirected ports etc... As long as it had started life as an XR casting, the AMA was happy... And if you think the other competitors weren't moding anything, look at it again!!! Obviously, if it had not been submitted/approved, you couldn't use it, like Dick Mann's G50 63' road race frame... The std Iron XR heads only had thinner cores put in during the casting and they made 200 pairs of them so they were definitively legal...

O'Brien knew exactly how far he could stretch the rule book, I don't think he would have cast new short cyls just for Branch to try yet another unproven mod... I think Jerry did them in his own time, probably as you describe it, except the middle core might have been pretty thick before welding the two end bits together to keep it all in line...

Patrick
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panic

Post Sun Jan 27, 2008 5:17 pm

Re: KR crank options?

I'm not surprised that the short rod motor didn't do well. That's the sort of change that looks good on paper, but requires almost every function to be re-thought, built, assembled and tested. Remember, this is a venue where builders sweat over "should I use the 5.7" rod or the 5.85" rod in my Chevy " - literally (ratio change of 2.6%); the ratio change here is huge: 1.951:1 drops to 1.689:1, a 15% change.
Shorter rod: less spark, more compression, later IVC, more intake duration, larger port, more port volume, more overlap, smaller LCA, more venturi area are a few of what would need to be reviewed (some changes will have minimal effect, of course). A few years should do it. What, the race is in 2 months? Do the best you can.
There are cases where a violent reduction in ratio works well. Unfortunately, there is a tendency to say "see, no problem - it will work on my Kaiser-Fraser just as well", when in fact it worked because the parent design had too much port and too large a ratio for the displacement (iron Sportster is the poster child), and why big-bore stock stroke Sportsters are notorious slugs.

"they made 200 pairs of them"
:roll: :roll: :roll:
I thought that manner of explanation was safely laid to rest after Enzo beat it to death claiming homologo status for half the special racers that left Maranello for 20 years.
They (the unctuous FIM officials) would timorously ask ("please, Commendattore, if it's not too much trouble?") if the required number had been made.
He would wait silently for perhaps 2 minutes, perhaps 3, and then answer "Of course".
Here ended the "official investigation", and off to Le Mans. Henry Ford II's head exploded when he heard this.

Some of those 200 Sportster head castings are still hematite ore in some mountain, IMHO. This is the racing department who couldn't afford to make a special piston, and had to use cam shapes without compensation for the roller offset in the XR because to change it costs money??

Gordon Jennings bitterly commented at the time that AMA appeared not to care that "the factory was playing musical castings".
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mike100m

Posts: 51

Joined: Fri Jul 23, 2004 12:01 am

Location: felton,Ca.USA

Post Sun Jan 27, 2008 5:45 pm

Re: KR crank options?

Patrick
Our late friend XLR, (Jim), had a fresh short rod motor that came out of the L. Andres stuff he ended up with. I believe Andres got it from Sifton. When I looked at this motor, you could see the cylinder had been cut, shortened and brazed below the ring travel area. Rods were shortened as mentioned above.
Mike




thefrenchowl wrote:Payton,

These KR short rods cylinders were even shorter than you might think, they had to have a vertical magneto as the front of the timing cover was deleted to clear the front exhaust stub!!! There's a good photo of the 1967 Aer-Macchi framed short rod KRTT in Stephen Wright American Racer 1940/80. It only managed 16th place during qualifying at 129.72mph, against Fred Nix's 1st post at 140,82mph

What you have are most probably KH/KHR cylinders that have been shortened for use on a K/KR... I've seen it done a few times, I even have a KH pair like that!!!

Panic,

the AMA said you had to use listed/submitted KR cylinders or parts, it said nothing about moding/welding/porting std KR cylinders or parts!!! Same for the atrocious Waffle Iron XR heads fitted with twin carbs and blanked/redirected ports etc... As long as it had started life as an XR casting, the AMA was happy... And if you think the other competitors weren't moding anything, look at it again!!! Obviously, if it had not been submitted/approved, you couldn't use it, like Dick Mann's G50 63' road race frame... The std Iron XR heads only had thinner cores put in during the casting and they made 200 pairs of them so they were definitively legal...

O'Brien knew exactly how far he could stretch the rule book, I don't think he would have cast new short cyls just for Branch to try yet another unproven mod... I think Jerry did them in his own time, probably as you describe it, except the middle core might have been pretty thick before welding the two end bits together to keep it all in line...

Patrick
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