Don Terrill’s Speed-Talk

I've noticed we all like to talk about cam profiles and camshafts. Most of the discussions revolve around today's camshafts. It is interesting how the early engine designers did not pay much attention to cam profiles. Some of the earliest engines did not even have an intake cam; only an exhaust cam that opened the valve at BTC and closed at TDC. It always amazes me how mechanical devices develop over time.

I'd like to know what Burt Munro's Indian cams spec'ed out at ...
old man esky has a set apparently .... so there's a little project you / ...me

Here is a paragraph taken from this web site http://www.dudeworld.com.au/ARTIBURTMUNRO.HTML

"Munro quit working in the late 1940s so he could devote his time fully to improving his Indian and Velocette racing bikes. During this period, he honed his skills at designing his own parts for the bike. Munro found unique sources for raw materials. As an example, the conrods he carved from caterpillar axles took five solid months to make and lasted over 20 years, through countless high-speed runs. He experimented with a variety of metals by trial and error, once melting down an old gas pipeline and combining it with other melted metals to cast pistons for his bike. He even made his own cams, often filing them by hand. From wheels, to engine parts to the streamliner's shell, Munro custom made just about every part of his bikes. It didn't take long for the Munro Special to have very little of the original Indian Scout remaining and it didn't take long for the records to start tumbling."

It's amazing what some people were able to do during a period when available resources were not plentiful.

The early motorcycle valve train was not as simple and straight forward as you might think. There was usually some type of bell crank or “rocker arm” that the cam profile acted on first.

On modified engines, the shape of the cam profile was created by hand without much regard for velocity, acceleration, and jerk values. Analyzing early cam profiles and any profiles made before the use of computers is less than exciting. There was just not the knowledge and resources available to design a modern cam profile.

ingram wrote:Here is a paragraph taken from this web site http://www.dudeworld.com.au/ARTIBURTMUNRO.HTML

"Munro quit working in the late 1940s so he could devote his time fully to improving his Indian and Velocette racing bikes. During this period, he honed his skills at designing his own parts for the bike. Munro found unique sources for raw materials. As an example, the conrods he carved from caterpillar axles took five solid months to make and lasted over 20 years, through countless high-speed runs. He experimented with a variety of metals by trial and error, once melting down an old gas pipeline and combining it with other melted metals to cast pistons for his bike. He even made his own cams, often filing them by hand. From wheels, to engine parts to the streamliner's shell, Munro custom made just about every part of his bikes. It didn't take long for the Munro Special to have very little of the original Indian Scout remaining and it didn't take long for the records to start tumbling."

It's amazing what some people were able to do during a period when available resources were not plentiful.

Yes I've read books and seen documentaries on Burt . being a Kiwi, myself ,,,these type of blokes are wound and entwined into our folklore
I don't know if Burt was a brilliant engineer, probably very clever and persistent
I've seen the genuine ' Munroe special ' it looked like the biggest piece of shit you could possibly imagine how you could ever get to 220+ mph is .....

ingram wrote:The early motorcycle valve train was not as simple and straight forward as you might think. There was usually some type of bell crank or “rocker arm” that the cam profile acted on first.

On modified engines, the shape of the cam profile was created by hand without much regard for velocity, acceleration, and jerk values. Analyzing early cam profiles and any profiles made before the use of computers is less than exciting. There was just not the knowledge and resources available to design a modern cam profile.

Those cam profiles are interesting, the reverse radius / follower combo is fasinating ... there was a pommie chap ' Taylor ' did a lot of work on this idea and the system eventually found it's way into a semi sports car engine ... it went v well

I think the idea is the flat tappet almost turn into a roller profile which allows tremendous V & A ... some thing I intend to study once I get my grinder done