Milwaukee Midget

[Stan Back]

Comments . . .

I was afraid you'd repainted the car from the previous video -- showed awful yellow -- now looks great!

Sings right along, doesn't it?  How much you feel the wheel discs add?

Stan

[Graham in Aus]

How about .1 HP/cc?

Oops!  Thanks Stan!   

Chris I take it the figure is at the wheels, but, no sweat, rolling roads are really only best for comparison of improvements, not the final figure!

[Milwaukee Midget]

How about .1 HP/cc?

Oops!  Thanks Stan!   

Chris I take it the figure is at the wheels, but, no sweat, rolling roads are really only best for comparison of improvements, not the final figure!

Graham, you're spot on with that assessment - yes, that's rear wheel horsepower.  I really don't know what kind of drivetrain losses are associated with a stock Spridget drivetrain, but for the moment, I'm more concerned about the power curve than the numbers.  The curve is very promising, if I can get the numbers up.

On the second pull, I was able to rev it in 3rd to where it didn't fall off of the table on the 3-4 shift - that will be critical.  Part of the plan all along was to build an engine that would rev well past peak and then fall back into the sweet spot - that's looking pretty good at the moment. 

Some of this is going to be dependant on me learning how to operate it.  It goes against my very nature to wind it up and let it fly.
I grew up with cars that were dependant on torque more than horsepower, so sitting behind a buzz-bomb turning 8-9 k is a bit unnerving. 

The good thing is that I had no discernible drivetrain vibrations during these pulls.  That might not have been the case if I wasn't keeping an eye on Ray the Rat a few months back when he munched his floorpan after a driveshaft failure.  I took it seriously, and now I'm now working with a decent, balanced driveshaft, a new yoke, new U-joints, and 2 driveshaft loops.  Toward the end of the pulls, I was in the upper 8's on the tach, which would translate to a rolling speed of ~135 with no vibration.  Usually, I'm the "other people" when it comes to "learning from other people's mistakes."  Ray, I'm sorry it had to be you, but I'm grateful for the lesson.


I intend to use the same dyno next spring.  They seem to do a decent job of maintaining their equipment. 

I wish Stan hadn't brought reality into the picture - I kind of like the idea of 1000 ponies! 

Killjoy . . . 

[Captthundarr]

Good for you Chris, it seems that you gained a wealth of knowledge from a few pulls. As for lessons learned, after the Ray The Rat incident I am fabbing a rear drive shaft safety loop as we speak.

[Milwaukee Midget]

Frank, thanks for that.  I tried to put some forethought into the approach, and went in with a plan.  I've picked up a lot of info from just chatting with folks like yourself and keeping an eye on the boards. 

With the dyno, when I saw where the A/F ratio was, I knew I didn't have enough jets in the tackle box to waste a lot of time messing with the carb, so that put the kibosh on any tweaks there.  But even the first pull, of which there is no video, where we weren't able to track the tach on the dyno, did get us information from our data logging, so Tim and I were able to use what would have been a missed opportunity to our advantage.

I also think that the guys at the dyno shop appreciated that.  They get a lot of knuckleheads in who are looking only for bragging numbers.  We came in prepped, and clearly didn't require any babysitting.  They were able to get other things done between our pulls.  I respected their time, they respected our efforts.  It was a very positive experience.

Drained the radiator last night - the Midget is now hibernating.     

[Tman]

Latches packed, hope to get them out to you today or tomorrow. Trent

[saltwheels262]

after the Ray The Rat incident

could the length of the drive shaft ( too short or too long )
been the cause of ray's problem ?

[Interested Observer]

Ref reply No. 799 dyno curve photo

Chris,
Given that the graphs are a bit too fuzzy to read the numbers well, and that I have no particular experience with chassis dyno results, it does, however, seem that there is an awful lot of chatter in the data.  It appears to be plus or minus about 10 percent or more--which seems like more than what one would like or expect from a reasonably well set up test tool.  Since there is quite a bit of inertia in the driveline, axles, wheels, and dyno rollers, to get that much variation over such short time intervals is puzzling. 

Did the dyno guys have any comment or explanation for it?  Was the car jumping around or surging a lot?
About how long did a pull take?  Was there any indication of oscillatory windup in the driveline?  Was the non-optimum carburetion giving the engine fits?  Do they keep an rpm record of the rollers?  If so, is it as ragged as the power curves?  If not, where is all the chatter coming from, flaky load cells?

Not a big deal, but based on other testing experience, with that much variation one would have to be a bit leery of the results.  At least until there is an explanation.  Granted that you weren’t looking for definitive results this time, but it might be something to get sorted out before the next go around.

[Bob Drury]

  Cris, one of the smartest people I have ever met (and one of Marlo's tribe of experts) builds Porshe race engines for racers allover North America, and has both a free standing dyno and a roller dyno.
  He has run many engines on both and says you can expect a 20 to 25% parasitic loss of horsepower between the two.
  In my case with a 4 speed Lenco (clutch plus 3 clutch packs and a quickchange rear end) I end up with about 200 h.p.............. just kidding, but it gives you a idea about lost horsepower.
  If I realize that I can't quite hit the record, first the quick change goes, then the Lenco. 
                                                         Bob

[Freud]

Elverude is a TREASURE.

FREUD

[Bob Drury]

  Amen Glen, and I have never felt worse than when I split my dry sump tank on his chassis dyno.  I owe Dicky bigtime for his help cleaning up that disaster............  Bob

[Milwaukee Midget]

Intrested Bystander, thanks for that comment.  I was told by Jeff, the operator, that he follows the the curve along the top.  I've taken his word on that, but I've never done any work on a dyno before.  I'd be happy to hear from anyone who has - and that's one of the reasons I posted the sheet.

The reading occurs in a ~1000 RPM range - 6800 and 7800, in 4th gear.  My thought is that we're probably seeing what would be the equivalent of a "pixilated" snapshot - so close in that the we're not seeing the big picture.  But am I seeing a forest when it's actually just a bunch of trees?

I can say that from the driver's seat, and backed up by the audio on the videos, it pulled smoothly and evenly.  I spent maybe 30 seconds in high gear, flat out, and reved well past the peak with no vibration or oscillation.  Other than the sheer noise of it, it was a remarkably uneventful pair of pulls.

But along your point, and looking back in hindsight, I would have also expected the A/F ratio to change at different points in the run, yet it stayed flat.  Maybe too flat?    At a 10/1 A/F indication, my plugs came back light grey/tan, which, now that I think about it, would indicate a normal combustion, not a rich mixture.  I guess I'm wondering now if there was an issue with the sniffer - the exhaust pipe and plugs should probably be black as charcoal.  Hmmmm . . .

Bob, yeah, the drivetrain is stock, the transmission design dates back to Sputnik.  I remember I started a thread a few years back asking about rear end efficiency - got a lot of info from that.  One of the keys was that the closer to the axle centerline was to  the axis of the pinion, the more efficient a rear end was likely to be.  I checked into Datsun, Nissan, Toyota, Ford, Mazda rears - the Midget was as good or better than anything else I looked at, so I stayed with the stocker.

And I've also wondered about the "percentage" of parasitic loss a drivetrain brings to the party.  It seems to me that it would be a constant, not variable with the output of an engine.  Why would doubling the output of an engine cause the transmission to require more horsepower? 

Submitted for peer review - you may fire when ready.  I'm not here to defend - I'm here to learn.

Thanks, guys.

Chris

[maguromic]

Chris, I think you meant to say Interested Observer not Interested Bystander.  Tony

[Milwaukee Midget]

Chris, I think you meant to say Interested Observer not Interested Bystander.  Tony

Oh, good lord - my apologies.

I've got to put together an LSR Rolodex.

[Dr Goggles]

Hey that Bill Veeck stuff was hilarious......a moveable wall! hahahahahahaha