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Old 03-08-2013, 06:31 AM   #151
chasbmw
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Dirk,

The reason why Motoren Israel gets the business is because they have a fairly good English language website and they will send items quickly and at a reasonable cost. I'm sure there are other suppliers of 320 degree small seal camshafts and 1st oversize Wossner pistons, but I can't find any of them on the web.

They also accept credit cards.

my knowledge of German is very limited and having an easy to navigate English website is something that many suppliers in Germany don't do very well. The ability to take payments by credit cards is also very important to customers because banks in the UK and I would assume the US, seem to charge large amounts of money for transferring money to Euro banks. Many of us English speakers are not very good at picking up the phone and talking to a company in Germany because we don't know if anyone at the other end will speak English.

I hope this is helpful and thanks for all the info you have provided.

Charles
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Old 03-08-2013, 09:33 AM   #152
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Hi Dirk,
I posted this a bit back and you missed it:

Quote:
Hi Dirk,
Thanx for dropping in and letting us pick your brain! We have some talented people here, but a lot are like myself, amateurs, not pro wrenches, or designers. So this is a treat!

I'm interested in the Sport-Street type CAMs that most would be interested in, and how they differ in their character.

These would be the various 320 varaints, the 324(which I have in a box), and the other sport street offerings by Edelweiss and MI.

The other observance that a lot of folks would like answered is this:

If I buy a CAM from Web or Isky, or others, I get complete specs with the CAM and all the check points are elucidated and mapped out for me. Why is this not the operating procedure for Beemer Cam grinders?

Thanx for your contributions here!
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Old 03-08-2013, 10:24 AM   #153
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Quote:
Originally Posted by Plaka View Post
ya gots that backwards partner. The modulus of elasticity of aluminum is around 10 million. it's 30 million for steels. The steel is 3 times stiffer. That's why aluminum bicycle frames use such fat tubes. You need to make the tubes a LOT bigger to get the stiffness of a steel tube. What can be confusing is the failure mode. Steel will bend where aluminum will fracture. This a function of ductility, not stiffness.
I completely agree, I think I was not clear. The reason bike frames are large tube is the inherent weakness of aluminum, however, the aluminum can be made into a tube so large, because of it's light weight. This actually makes for a tube that is stiffer than the steel tube bicycle, whose tube diameter is limited by practical wall thickness, and therefore weight.

The real problem with pushrods, is that due to space constraints the tube cannot be made as big as it needs to be to take advantage of it's weight advantage, which is why I was assuming it would rub, if made a larger diameter.
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Old 03-08-2013, 11:31 AM   #154
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Originally Posted by Houseoffubar View Post
Haha, Beautifully said Dirk!
Mr. know it all means well, he just rubs people the wrong way

On another note, aluminum is stiffer than steel, a lot stiffer, so it seems it would not flex much as a pushrod of any alloy of steel. The other issue is that aluminum will crack if cycled/flexed very many times. This leads me to believe they can't be flexing much, or they would rapidly fail.
That said the only explanation I can find for the rub marks, is that because aluminum is much weaker than steel, it must be made larger in diameter than the steel rods (wall thickness has almost zero to do with tube stiffness) causing them to make contact even with less flex than the steel push rods.

Peace!
That wasn't me talking about VW pushrods and broken rockers or saying there is no need for better pushrods and standard ones are OK. I have been saying just the opposite. Like Dirk, I have never seen any trouble with stock rocker arms either. I have seen aluminum ones break but that was years back. The first aluminum car rockers broke a lot too but not any more. I don't know about newer generation aluminum rockers for our engines.

Isn't it funny how most such comments are directed towards the wrong person?

supershaft screwed with this post 03-08-2013 at 12:41 PM
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Old 03-08-2013, 12:02 PM   #155
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Yes, the pushrods definitely spin. Quite a bit. You can see it. Our stock ones definitely flex too.

Steel versus aluminum? I just go by what I see. BMW aluminum rods flex a lot more than BMW steel rods as evidenced by the rub marks on them. That and research into performance pushrod companies with lots of race experience and for the most part you will find that they use 4130 and 4140 for more rigidity with less mass than other alloys. There has just in the last decade or so been a real revolution in pushrod engineering.

Out of respect for some people I know and have worked with, I know some people that would disagree about some of those airhead mods coming out of the same place in the last 20 years. Particularly substantially longer rod length ratios. So far, I don't know of anyone doing it with our engines before Dr. Curve? He freely admits he got the idea from Smokey Yunick who I think pretty much pioneered the concept to the degree that he did? Same deal with raised port floors as far as I can tell. Not D shaped ports but raised port floors right at the port's inside radius.

I think chasbmw is right about Dirk's business. I just ordered some stuff from MI versus Dirk's place simply because I understood their website better.

supershaft screwed with this post 03-08-2013 at 12:44 PM
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Old 03-08-2013, 07:40 PM   #156
Voltaire
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Re using aircooled VW ones, On the face of it they look much the same size but the rounded ends are different diameters VW 8.0 to BMW's 9.5.
To my thinking they would not be a snug fit.

The owner of the Triumph Trident at the track was horrified to learn that the BMW pushrods were 'nearly a foot long" , he gave me the name of his supplier in the States http://www.pushrods.net/
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Old 03-08-2013, 08:05 PM   #157
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Originally Posted by Voltaire View Post
Re using aircooled VW ones, On the face of it they look much the same size but the rounded ends are different diameters VW 8.0 to BMW's 9.5.
To my thinking they would not be a snug fit.

The owner of the Triumph Trident at the track was horrified to learn that the BMW pushrods were 'nearly a foot long" , he gave me the name of his supplier in the States http://www.pushrods.net/
They very well could not be rigid enough. Diameter, wall thickness and alloy will give you an idea.

I shopped there. They have a long history of making pushrods for airheads. A guy there told me that they use an American size tip that is real close to the same thing as the metric size. I have seen major problems with aftermarket pushrods. The main issue was the ball ends not being polished smooth enough and the rods boring right through the lifters. I don't know if having a 'real close' ball end fit was part of the problem or not. I am not going to take any chances.
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Old 03-08-2013, 10:30 PM   #158
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Us simple airheads tipes like pikchures better:

Solid 10mm steel pushrod:

http://www.cafebeemer.com.au/blog/Pu...Pushrod_FE.avi


As plaka and others pointed out:

For a given crossection, stiffness varies with Youngs Modulus 'E'

Aluminium: E = 72 GPa approx
Steel: E = 200 GPa spprox.

So steel almost 3 times 'stiffer' than aluminium. (note: E doesn't change much with hardness or alloying materials for a given parent material)

Solid 10mm aluminium pushrod subjected to exactly same forces as above;

http://www.cafebeemer.com.au/blog/Pu...Pushrod_AL.avi

It flexes a whole heap more under same load but, crossection has a far greater effect on stiffness than E due to a squared relationship. (which is one reason aluminium bike frames are made from larger sections.)

So, if you taper the aluminium rod (ala Airhead Wrangler post) from 10mm to just 14mm at the middle you get this with same forces:

http://www.cafebeemer.com.au/blog/Pu...AL_Tapered.avi

Which is deflecting a little less than the steel rod for a weight advantage of about 42% even though the thing is fatter!
So, the increase in diameter has more than compensated for the low E of aluminium compared to steel and is far lighter.

Reducing pushrod weight is advantageous due to mass acceleration issues and implications for wear. It can even effect valve float depending on engine configuration.

There are other condsiderations in the design of pushrods (coef of thermal expansion is a biggy) but from a stiffness/weight point of view, tapered aluminium rods win hands down.

Mmmm, do I detect a taper in Dirk's bright aluminimum looking rods?
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Old 03-08-2013, 10:41 PM   #159
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That's what a smart guy sounds like, instead of the idiotic drivel coming from my mouth!

That is what I was trying to say, thank you adrian for so eloquently stating it!
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Old 03-09-2013, 02:07 AM   #160
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Quote:
Originally Posted by Voltaire View Post
The owner of the Triumph Trident at the track was horrified to learn that the BMW pushrods were 'nearly a foot long"
BSA Goldstar (& B31 & B33) are about the same length too. Valve timing on the Goldstar is about some of the most extreme ever, although I don't think they were pushed much beyond 7,000rpm.
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Old 03-09-2013, 05:21 AM   #161
adrenal
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Quote:
Originally Posted by Houseoffubar View Post
That's what a smart guy sounds like, instead of the idiotic drivel coming from my mouth!

That is what I was trying to say, thank you adrian for so eloquently stating it!
Yeah man, and your beautiful welding and frame mods are double drivel!
(p.s. thanks for your kind words)
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Old 03-09-2013, 01:12 PM   #162
supershaft
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Quote:
Originally Posted by adrenal View Post
Us simple airheads tipes like pikchures better:

Solid 10mm steel pushrod:

http://www.cafebeemer.com.au/blog/Pu...Pushrod_FE.avi


As plaka and others pointed out:

For a given crossection, stiffness varies with Youngs Modulus 'E'

Aluminium: E = 72 GPa approx
Steel: E = 200 GPa spprox.

So steel almost 3 times 'stiffer' than aluminium. (note: E doesn't change much with hardness or alloying materials for a given parent material)

Solid 10mm aluminium pushrod subjected to exactly same forces as above;

http://www.cafebeemer.com.au/blog/Pu...Pushrod_AL.avi

It flexes a whole heap more under same load but, crossection has a far greater effect on stiffness than E due to a squared relationship. (which is one reason aluminium bike frames are made from larger sections.)

So, if you taper the aluminium rod (ala Airhead Wrangler post) from 10mm to just 14mm at the middle you get this with same forces:

http://www.cafebeemer.com.au/blog/Pu...AL_Tapered.avi

Which is deflecting a little less than the steel rod for a weight advantage of about 42% even though the thing is fatter!
So, the increase in diameter has more than compensated for the low E of aluminium compared to steel and is far lighter.

Reducing pushrod weight is advantageous due to mass acceleration issues and implications for wear. It can even effect valve float depending on engine configuration.

There are other condsiderations in the design of pushrods (coef of thermal expansion is a biggy) but from a stiffness/weight point of view, tapered aluminium rods win hands down.

Mmmm, do I detect a taper in Dirk's bright aluminimum looking rods?
Yes, Dirk's rods are tapered.

I just recently made a number of calls and quite a bit of research in not metallurgy but high performance pushrod manufacturers and what tuners are using. All of them found just the opposite in theory and practice. Most all the big money pushrod engine tuners are using tapered rods in 4130 and 4140 two to three times heavier than mostly 4130 rods of just a few years ago from what I can tell. My 4130 rods are not tapered but Manton advised me that there was no need to taper 4130 with my wall thickness at spring pressures anywhere close to what I am running.

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Old 03-09-2013, 01:26 PM   #163
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Certainly no need, but from what info Dirk has offered, a benefit for sure.
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Old 03-09-2013, 03:08 PM   #164
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Your models show solid push rods. What affect is there when they are hallow? The increased surface area should increase rigidity of the unit.
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Old 03-09-2013, 06:14 PM   #165
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Quote:
Originally Posted by supershaft View Post
Yes, Dirk's rods are tapered.

I just recently made a number of calls and quite a bit of research in not metallurgy but high performance pushrod manufacturers and what tuners are using. All of them found just the opposite in theory and practice. Most all the big money pushrod engine tuners are using tapered rods in 4130 and 4140 two to three times heavier than mostly 4130 rods of just a few years ago from what I can tell. My 4130 rods are not tapered but Manton advised me that there was no need to taper 4130 with my wall thickness at spring pressures anywhere close to what I am running.
I don't profess to be an expert in pushrods by any stretch. There are no doubt lots of considerations identified by people who make pushrods their living about which I haven't a clue.

Strength of materials is part of my living and in this area the numbers speak for themselves. What's important in all of these technical discussions, is to clearly define your objectives. If you don't, then things can go round and round n rou... as is so often the case in so many threads. If you are talking stock or mildly hopped airheads then what Manton advised could be true.

However, the following statements from Dirk had me springing from my lurking cupboard: ' Now we can rev up to 10.000 rpm and the engines feel like overhead cammed - never crashing any valve at lifts you would not believe.' And: 'They are able to transport the cam information 1:1 from the cam to the valve...and this is more then essential and makes it perform like an overhead cam engine. Very silent, very smooth and very strong.'

To the computer! Took a punt on forces and did some FE modelling in the contex of high performance airheads aiming to minimise flex. The absolute numbers are less important than the relative results between materials and cross-sectional area. Not sure if 14mm at midpoint of rod will interfer with the tube but wouldn't be far off I reckon.

Anyway, for me it was an interesting exercise that corroborated what Dirk was saying.

BTW: Thanks Dirk, your contribution here has been fascinating.
Doch, Britten und Tesla rock!
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