Sunday, October 21, 2012

EL Bonnie on the Dyno

Last stop for EL Bonnie before hitting the "great white dyno" AKA the Salt Flats, was a mechanical dynomometer.  Like much of the rest of the project, this too proved to be somewhat less straightforward than planned.  Faribault Harley Davidson had come on board as a sponsor in the form of providing dyno work.  Only one problem; about the time Joe and Terry were feverishly working to install the modified 61 inch motor in the EL Bonnie chassis, the FHD dyno was in the process of taking some time off (I think the term technical description was that "it blew up").  Since repairs to the Faribault  dyno were not possible in time for the Knucklehead, another plan was needed.

A call from team member John Endrizzi to Pat Lehmann of Rochester Harley saved the day.  Pat graciously agreed to come in on his day off to establish the baseline jetting using their SuperFlow Dyno.

The following video documents some of the dyno testing.  A couple notes about the video; the first thing that you may notice is the ingenious starter system that Joe Taylor came up with.  It consists of a snow blower with a go cart wheel attached in place of  the rotor.  Also noteworthy  is that when you see Pat with the welding gloves on, it is because the plug wires kept coming loose from the magneto at RPM.  Eventually he was forced to hold them in place during the dyno run.  Finding this one issue alone, before making the trip all the way to the salt, was priceless.


So, what was the horsepower?  I guess we just don't know.  I knew going in that the dyno would probably not pick up a usable trigger from the magneto.  The lack of a tachometer on the bike was also an issue.  After some initial warm up runs and jet changes, Pat broke out an optical pickup which he set up to run off the engine pulley, but since he had never had occasion to use it before, there was some question as to the readings it produced.  The actual readings showed over 120 horsepower at around 4800 RPM - obviously that was incorrect (at no time during the dyno session did the engine reach maximum RPMs).  The RPM readings from the optical pickup seemed to be right though.
 
After the fact I mathematically calculated the RPM from the wheel speed, confirming that the optical pickup was providing accurate data.  If the horsepower readings  we saw meant anything, my guess is that they were reading double the actual horsepower figure, but since the engine was only taken to about 4800 of what I hoped would be a 7500 RPM top, even that told us very little.
 
Oh well, perhaps the great white dyno of the Bonneville Salt Flats would provide more conclusive results...
      

11 comments:

47str8leg said...

That thing sounds insane! Is it streetable at all? A knuckle at 7500 rpm must be off the charts! White Knuckles would be a more apt name for the man w/brass balls big enough to set sail on that spaceship.

Tim

Knucklenutz said...

Lee will be doing an EL build for me in the near future. In some ways it will mirror EL Bonnie. But make no mistake, EL Bonnie is NOT a street bike. The howl that you heard from EL Bonnie was derived from approximately 3/4 throttle. Hopefully we will have the bike ready to run at the April ECTA Land Speed Racing event at Wilmington Ohio at the end of April. Possibly there will be a full throttle dyno video from Lee's camera before then.

St. Lee said...

Tim, the one thing that really rules it out from street use is the extreme lightening of the crankshaft. I don't know that anyone tried kick starting it, but my guess is that it would be very hard to do with so little "flywheel effect."

Oh, and that name was already taken - I ran a 120 cubic inch supercharged Knuckle dragbike that I called the "White Knuckle Express". (guess what color it was)

John, guess I better get back to work on it...

47str8leg said...

That's right ,I remember now, brake rotors for flywheels!What,you can't have a chase truck w/ a snowblower in it?

Tim

pat said...

that was a lot of fun. when the engine goes back together you guys are more than welcome to bring it back to the dyno. i'll make sure i have the optical pickup working properly so we can measure power as changes are made.

St. Lee said...

Pat, if I'd thought you would read this I'd have been even more nervous that I spelled your name wrong! Thanks again for helping the guys out with the dyno work - you are a life saver.

Knucklenutz said...

Chris Callen included El Bonnie in his coverage of the 2012 BUB Speed trials in the December issue of Cycle Source Magazine pp76-80.

47str8leg said...

Go over to the greasy culture website and check out the vintage hillclimbs and drags from the 50's. At 4:13 there's a knucklehead rail dragster!

Tim

St. Lee said...

Thanks for pointing that out, Tim. I had watched that video before, but missed the Knuck engined rail. That would almost have to be Pete Hill. Early in his racing career his local track had outlawed motorcycles, so he did the next best thing by putting a Knuck engine in a rail.

Knucklenutz said...

I can't find the video. Could someone please provide a link ?

St. Lee said...

Here John. This link is directly to the YouTube video;

vintage motorcycle films home movie