Penton 100 vs CZ 125

[brian kirby]

This is a neat sequence of photos my Mom got from Barber. This is Classic 125 and I am racing a trick CZ125 with my Berkshire.













He had been blocking me a little bit, so I decided it was time to get by. I went outside in the left hander right before the pics start to get to the inside of the right hander you see. We bumped a little in the corner, but I didnt drift wide, he tried to chop down on me and make me shut off, but as you can see that didnt work.



Brian

[Dale Fisher]

More of the story?











1972 Cheney Sachs
1972 Suzuki GT380
1972/73 Cheney Sachs Project
1973 Triumph TR5MX
1973 Penton Jackpiner Project
1974 Penton Berkshire
1974 Honda MT125

[brian kirby]

Yes Dale, that is the conclusion. I made that pass on the second to last lap, and your sequence is the last corner last lap. In the little straight before that lefthander at the finish I could hear him, and when I shut off for that corner I heard him in the gas WAAAAAY longer than me. When I heard that I knew he would never make that left, so I did not turn in. It was a smart move because he would have T-boned me if I had turned in like normal. It was a kamikaze move on his part, but I guess he was a little upset with me, which I dont know why, I didnt go wide and push him out, he cut down on me. Now, I did not back off or give him any room which caused us to bang bars, but its not my responsibility to back off and give him room if I have the inside.

Brian

[Larry Perkins]

You know the old MX saying, "There is one rule in motocross, and everybody forgot it."

Once the gate drops or the band snaps it's MX, it's war, it's a ground possesion game.  No blood no foul.  Bars were meant to be banged.  That is war in the trenches hand to hand.  I'm ready, put me in coach.

Larry P

[Lloyd Boland]

Brian, it looks like you had a little advantage in the horsepwer to weight ratio???  

But when it comes to bumping, sometimes the greater the weight wins, I should know, but I am now down 37 pounds.

Hoping for greater speed and less bumping.

[wfopete]

Looks like he was trying pull off a Communist "Block"

Pete Petrick
175 Jackpiner
Slow but Good

[Dale Fisher]

Banging bars, locking horns, I have the sudden urg to go hunting for some reason.  Without a doubt a "somebody's going to crash" move on his part (in this case him). Done in full view of Dave Lamberth with the checkered flag in hand....

1972 Cheney Sachs
1972 Suzuki GT380
1972/73 Cheney Sachs Project
1973 Triumph TR5MX
1973 Penton Jackpiner Project
1974 Penton Berkshire
1974 Honda MT125

[firstturn]

Nice job and great pictures.  Thanks Brian for all the hard work you do to make Penton bikes stand out and thanks for Ernie for never giving up on the Sachs power.  Makes me feel like I am back in 1974.

Ron Carbaugh

[Dale Fisher]

More from Luana and Brian's FB page.  First moto 100cc class







1972 Cheney Sachs
1972 Suzuki GT380
1972/73 Cheney Sachs Project
1973 Triumph TR5MX
1973 Penton Jackpiner Project
1974 Penton Berkshire
1974 Honda MT125

[brian kirby]

Larry, I agree, its war when the gate/band drops but not everyone sees it that way. I pride myself on being a "clean" rider, and it is a rare day indeed when you see me touch another rider while making a pass, but at the same time I'm NOT going to back off either.

Lloyd, I weigh a good 40-50lbs less than the CZ rider, and my 100 is very fast for a 100 so the power/weight was definitely in my favor.

Dale, on any other bike I get terrible starts, but for some reason on my 100 I always get good starts. I have it geared so I can start in 2nd which lets me avoid the 1-2 shift, so thats a big help.

Brian

[firstturn]

Let's just review that you are racing a 100 against a 125 CZ right?  So you have given him back the weight advantage.  Great job Brian.

Ron Carbaugh

[Jeff Vlk]

The CZ rider is Bruce Rounsaville. He has some of the best CZ in the country.

[joe novak]

Thank you for sharing the great photos of the CZ and Penton.  I enjoy viewing the not-so-common motorcycles on the off-road.  I think the variety of motorcycles on the starting line is what makes it more of a race.  Sort of a manufacturer vs manufacturer race as well as a man vs man.   joe

[Lloyd Boland]

Brian, someone once told me everything being equal, it takes 1hp to counteract every 7-8 pounds in weight a rider puts on.  I know we have some engineers out there, is there any truth to this?  How much horsepower does it take to counteract added riding weight?  

BTW, great pictures.

Lloyd.

[linglewn]

This is an interesting analytical question. Technically, one horsepower is equal to 550 foot pounds per second, or the power required to raise 550 pounds one foot in one second. If you run the numbers, 19 HP would raise a 400 pound bike/rider combination at a rate of 26 ft/sec. If the weight were increased by 10 lbs, it would take 19.38 HP (less than one additional HP).

Also, the force,or torque, required to accelerate the bike/rider mass is proportional to the weight and acceleration (hole shot). A 10 lb weight increase would take about 2.5% more horsepower or about 19.48 HP for the same acceleration as the 19 HP example.

Obviously this is all theoretical and there are real world forces that must also be considered. Also, we all know that it is easier to drop the weight than to coax extra horsepower out of a two stroke-cheaper too.

One of the more obvious questions here is how was the 19 HP determined. There are all kinds of HP numbers quoted for different engines with no indication as to how the numbers were generated. Were they calculated, guessed at by the seat-of-the-pants method, tested on a dyno at the engine output (Ron's question), or tested at the rear wheel. All will give different answers.

Nelson Lingle
73 Jackpiner
74 Jackpiner
71 DKW 125