Board index Flathead Power-Technical Questions, Answers, and Suggestions K-Models Leonard Andres short rod KR

Leonard Andres short rod KR

Post Tue Dec 06, 2011 5:37 pm

Posts: 52
Location: felton,Ca.USA
Greetings. I have finally started the resurrection of the Andres short rod motor we recieved in the stash of parts we bought from Jim," XLR's", estate.
I have sent Patrick pictures that he has agreed to post for me.
As you will see from the pictures this modification was quite an undertaking. The person that did the brazing was certainly extremly skilled. It appears that the cylinders were first bored out for a sleeve then shortened and sleeve was pressed in against a shoulder, which is the dark area at top of cylinder bore shown in picture, and flange installed all brazing done and the final machining.
I did find out fom another racer from San Diego, Ca., Jim McMurren, who was close friends with Cal Rayburn that these rods were actually machined from scratch and not shortened stock rods as most others did. Jim said Leonard actually hired the machinist and purchased equipment for him to work with.
One problem I did not think of before inspecting these parts is the neccessity of offseting the threaded o-ring collars on the lifter bosses so the lower spring covers line up. Again you can see this mod in the pictures. Also the main bearing on the timing side has been modified to use the same size bearing as drive side. Crankcase bored out and steel sleeve installed. Timing side crank pinion shaft converted to press-in instead of taper w/nut. I believe the very early XR's used this style shaft.
I am in the process of trying to find out how this motor would have been raced, if at all, ie: RR or dirttrack, or just a dyno mule. We intend to build it into a complete bike. I am in the process of trying to contact Mel Lacher who rode for Andres in the time period this was built. Mel was a very fast Ascot specialist so I'm hoping the motor was used in a dirttacker, a lot easier and cheaper to build than a KRTT.
I will keep you all informed with updates as I proceed.

Mike

Post Wed Dec 07, 2011 1:29 pm

Posts: 591
Location: Crewe, Great Britain

Thanks Mike for these updates on a most special motor...

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Patrick

Post Wed Dec 07, 2011 3:09 pm

Posts: 52
Location: felton,Ca.USA
Thanks Patrick for posting the pictures.

Post Sat Dec 10, 2011 11:49 pm

Posts: 2688
Location: Los Angeles, CA
Enlighten me about a short rod engine. What is the benefit? :?:

Post Mon Dec 12, 2011 12:57 pm

Posts: 52
Location: felton,Ca.USA
Chris
Since you asked. Here you go. Very good in depth answer to your question.
Mike
http://www.stahlheaders.com/Lit_Rod%20Length.htm

Post Mon Dec 12, 2011 10:43 pm

Posts: 87
Often a picture can be useful in understanding a particular mechanical system. To that end a plot was created showing the instantaneous piston velocity of a long rod (R/S ratio 2.0) and short rod (R/S ratio 1.6) KR engine at 6000 rpm. These extremes were used since they were called out in the reference article and furthermore bound the limit of practicality.

The plot allows the reader to visualize where and when differences in piston speed occur, during a single rotation of the crankshaft, as a result of the subject geometry changes (short and long connecting rods). In the plot crankshaft angles of 0 and 360 degrees refer to TDC. Hopefully this will assist in better understanding the reference article.

KR Piston Speed.jpg

Post Tue Dec 13, 2011 12:39 pm

Posts: 591
Location: Crewe, Great Britain

Std KR rod ratio is 1.95 (7.437/3.81)

AFAIK they shortened the rods by a max of 1", that gives new minimum ratio of 1.68 (6.437/3.81)

I like the engineering involved in this KR endeavour, but it seems like a LOT of work for very little improvement!!!

From what the oldies that rode them short rods say, it did not help the oil scavenging one bit, in fact quite the contrary...

Now, short stroke would have yeilded more bhp but sv bores can't be changed that easily...

Patrick


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