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Old 01-25-2011, 08:06 AM   #46
pommie john
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Originally Posted by moorespeed View Post
my 980cc sidecar race engines have about 100bhp at the wheel thats over 110 at the crank and the standard clutch with a heavy spring has no hope.

With that amount of power I'd be worrying about whether the gearbox can take it, especially with the weight of a sidecar to push around.
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Old 01-25-2011, 10:57 AM   #47
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Originally Posted by Rob Farmer View Post
Post 39 above is Richie Moore. I was implying you could ask him where the extra performance comes from with the long rod engine.
Like I said earlier. I have BTDT myself with Chris and his dyno as San Jose BMW. Dr. Curve helped Chris get into longer RLR setups. Some of Chris's engines owe a lot of their power to longer RLR's. I have talked with Chris quite a bit on the subject while we are dealing with them and Dr. Curve a little. PLUS I have read every bit of print that I know of by Smokey Yunick and Dr. Curve on the subject. As far as I know, Yunick pioneered the mod in cars and Dr. Curve was the first to transfer what Yunick did with cars over to long rodding airheads. I think Yunick got some of his RLR knowledge from Leo Goosen who was Harry Millers and then Offenhauser's main and only engineer. Goosen is I think this countries FOREMOST engine designer. From what I can tell and my experience with longer RLR's, I think they understand what is going on better than most. Sorry but I don't feel the need to ask Richie anything. I have heard his line of thought many times before if it is what I think it is.

supershaft screwed with this post 01-25-2011 at 11:13 AM
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Old 01-25-2011, 12:12 PM   #48
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Originally Posted by Rob Farmer View Post
I'm not thinking that. Richie says his rods are 15mm longer and he makes the shorter piston to counter that. The gains come though higher compression pistons and more efficient thrust angles.

The guys having work done by him seem really pleased with the results and he seems like a genuine open guy.
I just thought of another way to counter the notion that longer RLR's owe their gains to more efficient thrust angles: Piston pin offset.

Again, I have seen this phenomenon play out with my own eyes on a dyno as have many others. Most all production engines have offset piston pins to reduce piston cock and noise. Reversing that offset increases piston cock and noise but creates more TDC piston dwell just like a longer RLR will AND it will also increase higher RPM power. I have helped set up airhead engines that had both longer RLR's AND reversed piston pin offset for more power. One mode decreases torque producing angularity at the crank/rod and the other one increases piston side loading and yet they BOTH net increased higher RPM power. IMO, that leaves increased piston dwell at TDC and better cylinder filling through longer RLR's and piston pin offset being the primary causes of power gains .
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Old 01-25-2011, 12:43 PM   #49
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i can understand that you dont want to ask me any questions, thats ok. but how did you get your clutches to hold. i tried all the usual tricks inc the k75 pressure plate but still no good. i then had help direct from sachs race engineering Germany. thay gave me all the information on the springs pressure plates and cover plates from all the models that would fit, and all the combinations of the above. the spring pressure was not the real problem, it was the friction material due to the lack of asbestos,once the heat builds up to 150 degrees c which happens with micro slippage the coeficient of friction is lost. the organic material is just not good enough for desert racing or sidecar racing. i had a fellow competitor last year saying he had about 10 bhp moore than me with no clutch problems and it had me worried untill we raced him and we were 10 seconds a lap quicker,and it was just b/s bhp.
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Old 01-25-2011, 12:59 PM   #50
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Originally Posted by moorespeed View Post
i can understand that you dont want to ask me any questions, thats ok. but how did you get your clutches to hold. i tried all the usual tricks inc the k75 pressure plate but still no good. i then had help direct from sachs race engineering Germany. thay gave me all the information on the springs pressure plates and cover plates from all the models that would fit, and all the combinations of the above. the spring pressure was not the real problem, it was the friction material due to the lack of asbestos,once the heat builds up to 150 degrees c which happens with micro slippage the coeficient of friction is lost. the organic material is just not good enough for desert racing or sidecar racing. i had a fellow competitor last year saying he had about 10 bhp moore than me with no clutch problems and it had me worried untill we raced him and we were 10 seconds a lap quicker,and it was just b/s bhp.
Questions about piston dwell versus thrust advantages I mean.

I have NO experience running 100hp in a hack. You might have to go to a multi-plate clutch like real race cars use!

A good friend of mine was probably running around 75 or maybe even a bit more hp in a hack with as far as I know a stock late model clutch with no issues.

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Old 01-25-2011, 01:01 PM   #51
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I agree with the longer dwell as I said in post 39 I just do not to go into detail because most people dont understand all they wont to know is do they work and how well do they work, followed by how much are they. there is no point in trying to look clever on here just build an engine and race, it will speak for itself.
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Old 01-25-2011, 01:20 PM   #52
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Originally Posted by moorespeed View Post
I agree with the longer dwell as I said in post 39 I just do not to go into detail because most people dont understand all they wont to know is do they work and how well do they work, followed by how much are they. there is no point in trying to look clever on here just build an engine and race, it will speak for itself.
Look clever?? On the idiotnet? You will just have to believe me that that is no concern of mine. No googling!

I am just trying to nip common misunderstandings in the bud so I have to deal with them less in my shop. . . . And try to help people better understand what they are talking about.

I thought I would add that I was going on what RF said you said about RLR's gains which was angles. I didn't realize you went on more about dwell. Sorry!

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Old 01-25-2011, 02:59 PM   #53
pommie john
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Originally Posted by moorespeed View Post
how did you get your clutches to hold. i tried all the usual tricks inc the k75 pressure plate but still no good.


I use the K75 pressure plate and have no problems. It needs careful adjustment and there's a fine line between dragging and slipping.
Depending on which dyno you believe, my engine peaks at 66 or 76 ft/lbs.
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Old 01-25-2011, 03:35 PM   #54
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Originally Posted by pommie john View Post
I use the K75 pressure plate and have no problems. It needs careful adjustment and there's a fine line between dragging and slipping.
Depending on which dyno you believe, my engine peaks at 66 or 76 ft/lbs.
I completely hear you about different dynos AND different dyno operators! From what I can tell with brake dynos, I think you can get into the brake full on and crack the throttle just right at the right rpm and get an early and unrealistic torque spike in the curve.
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Old 01-26-2011, 03:40 AM   #55
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I completely hear you about different dynos AND different dyno operators! From what I can tell with brake dynos, I think you can get into the brake full on and crack the throttle just right at the right rpm and get an early and unrealistic torque spike in the curve.
Yeah. I've had reasonably consistant results from Dynojet dynos and I've been to four or five different ones, but they are reputed to read higher than brake or eddy current dynos.
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Old 01-30-2011, 09:05 AM   #56
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Originally Posted by supershaft View Post
Like I said earlier. I have BTDT myself with Chris and his dyno as San Jose BMW. Dr. Curve helped Chris get into longer RLR setups. Some of Chris's engines owe a lot of their power to longer RLR's.
Hi!

Now that would be very interesting.
AFAIK Chris Hdgson has experience both with shorter rods (125mm) and long rods. So he should be able to compare the effects.

A while ago he opened a thread about his cafe racer.
Then I was wondering why he didn't use long rods in his cafe racer, having read every bit of information from Dr. Curve before. The pistons seemed to be shorter so he should have been able to use longer rods. But in his thread he didn't even mention longer rods ...

Does anyone know?

Greetings from Rermany,

Rudi
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Old 01-30-2011, 09:06 AM   #57
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Originally Posted by supershaft View Post
As far as I know, Dr. Curve was the first one to draw up shortened pistons for Venolia to make specifically for an airhead.
AFAIK Udo Gietl already used very short pistons in his airhead racers. But he combined them with shorter rods (125mm).
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Old 01-30-2011, 09:20 AM   #58
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Originally Posted by supershaft View Post
The problem with those big bore kits is that the cylinder studs are in the same place as ever. The cylinder wall along the length of the cylinder's stud hole is paper thin as is the gasket area between the stud and pushrod tube holes and the bore. Plus the entire cylinder wall is way too thin to boot. I have seen big bore cylinders distort like a corrugated pipe 100% in unison with the cylinder's cooling fins!
Here im Germany Big Bore kits with 97mm bore are known to be trouble free. For example HPN offers them with shorter pistons, Scherb with original piston design (as far as length is concerned).
I know quite some guys now having the Siebenrock BB kit and no negative feedback so far.

The RLR discussion is really no topic here.
Only Dirk Scheffer (http://www.edelweiss-motorsport.de/) favors longer rods and his engines seem to be very strong. He states to have reached over 120 PS with 1200ccm displacement.

Greetings, Rudi
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Old 01-30-2011, 11:10 AM   #59
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Originally Posted by RGregor View Post
Hi!

Now that would be very interesting.
AFAIK Chris Hdgson has experience both with shorter rods (125mm) and long rods. So he should be able to compare the effects.

A while ago he opened a thread about his cafe racer.
Then I was wondering why he didn't use long rods in his cafe racer, having read every bit of information from Dr. Curve before. The pistons seemed to be shorter so he should have been able to use longer rods. But in his thread he didn't even mention longer rods ...

Does anyone know?

Greetings from Rermany,

Rudi
I believe it does have long rods but he didn't mention it.

All of his later efforts had longer rods in them, not shorter.
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Old 01-30-2011, 11:17 AM   #60
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I believe it does have long rods but he didn't mention it.

All of his later efforts had longer rods in them, not shorter.
Looking at the picture I would say it's about stock length:
http://www.advrider.com/forums/showt...t=sjbmw&page=2

Scroll down a bit.
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