Milwaukee Midget

[jacksoni]

You might consider getting a push off to about a 100 MPH to at least the one.  And then use the two gears that are the closest together with an appropriate rear gear.  Just a thought, probably not a good one.

well I do remember some wag announcer saying my push truck was trying to get a timing slip too. First long course run after qualifying on the short and the throttle cable had come loose so pas de power. Now I get scared with my big pickup pushing me to 50 for fear of getting sideways and T-boned. Other than that, sounds like a plan to me Stan. 

[Milwaukee Midget]

Well - Here's the spreadsheet. I think we can pull past the 3-4 shift point so that we're above 9,700 in third, and continue to pull at 7,800 in 4th to the point where we can continue to climb - for a little while, anyway -

4.22excel by Chris Conrad, on Flickr

For what it's worth, I DO have a set of shorter tires I might be able to use.

[Stainless1]

Well it looks to me like you rev 3rd to 11000 and you are getting close.... Don't pay too much attention to peak torque... shift when you start running to close to max RPM... that keeps you in your max HP area.  If you set a record without getting to 4th then you might try shorter tires... Don't get too low in the power band.

[Koncretekid]

I'd use the 4.55 rear gear to get you to 130 at 9030 rpm and with a little luck, it will keep pulling!

Tom

[jacksoni]

At 9000 you are only a few ponies above the grenade. If 4th is direct drive (don't know with your trans) it would be better to use that than 3rd, but getting the rpm's up to where peak power is would be more important than the bit of loss through the trans in 3rd. Way I see it you have couple of options: 1) since this is new combo and some things are uncertain (actual power and power peak etc), just pretty much run it as is and see what happens, perhaps with the smaller tires and then with more time and $ and etc, make changes for next year. or 2) figure that the power peak nearer the 125 predicted in the past and near the flash 122-3 Mark mentioned and that power peak is >10k somewhere, go ahead and do what you can to gear for it (gear plus smaller tire) to try to get it into the real  peak power range and see what you have then. I expect you have gone through these machinations/calculations. Will be interested to see what you decide and then of course the results. Am sorry I am going to SW instead of WOS and won't see you run but will be there in spirit in any case.

[Rex Schimmer]

Chris,
Your information well illustrates one of the advantages of EFI and that is the ability to run very close to the fuel stochiometric limit and get max power.  For us that are running "sprinkler" injection (read mechanical) we have to be much more conservative on where we set or air/fuel ratio. My friends that run gas typically run in the 12.3 to 12.6 area simply to ensure that the tops of the pistons don't go out the exhaust. On our little 1 liter Kawaski that we run on methanol we try for 6.0 and the stochiometric is 6.8. We have also found out that we don't find any power in a lot of advance as we run 30 degrees and don't see any reason (more power) to run more. Although we do have a 6 speed tranny the step from 5th to 6th is a little bit more than we would like to have and our plan is to make the 5 to 6 shift in the 12,800 to 13,000 rpm range. Our max power is in the 12,000 to 12,500 area.

Several years ago the J gas streamliner of Brant and Speranza came out with a new and better body, they were running a 660 cc Honda, so they were giving away 90 cc to the J class limit, any way they made several runs and were faster than their old body but still not a record breaker, suddenly they are running 218 and 220 speeds much faster than the record. I went over to see what they had done and it was all in the gearing. They changed the gear to allow the engine to rev to the 15,000 to 16,000 rpm range! but that was where it made its best horse power and they set a very impressive new record. It is horse power that makes you go fast not torque.

Rex

[Stainless1]

The 1 liter that Pork Pie set his record with was running 13.3 - 13.4 AFR...  Pentroof 4 valves like to be a bit leaner than the 2 valves that like that 12.2 range....
It sounds like the motor likes the revs, the limit is the valve train... if Mark thinks it has the spring to run 11 or 12K then you might want to go there... after you try 10K and hopefully set the record.  The 1K Porkpie used reved to 12.5K, I had Pork Pie shifting at 11.8K.  When we put it in BJ Burkdoll's truck we turned it up to 13.2 and shifted at 12.5.... It is still together...
Hey it's just a race motor... rev the piss out of it, that's where the HP is.

[Milwaukee Midget]

Bob - Rex - I'm not nearly as worried about the engine as I am worried about this -

20210617_205234 by Chris Conrad, on Flickr

If this were a streamliner or a lakester where I did not have to worry about drivetrain compliance with respect to suspension travel, I'd lash it to a Hewland Mk-VII and be done with it.

But while it is short (23 1/2"), lightweight and recently serviced and balanced, I question the wisdom of 10K with a live axle on leaf springs.

The transmission has 17 passes on it at Bonneville after a rebuild with straight cut gears. I'm thinking of having a scraper tack welded to the inside cover to alleviate windage - especially seeing as it's likely I'll need to spend more time in the lower gears with higher input shaft revs.

Yeah, I know - I'm not running a mid-70's late model at Knoxville, and it's not going in a stern-drive speed boat. Even when the big boys rut the salt, it tends to be smoother than the alley behind my house - but I do think I need to proceed with some caution.

Talk it through - think it through . . .

It all comes back to Harold's quote - "Problems are almost always a sign of progress".

[jacksoni]

Although I don't know the specs on that shaft ( guessing 2.5" and what, .083 wall steel?) at less than 24" the critical speed per various calculators suggest it is way higher than your expected RPM.  But, having lost a driveshaft at speed (130 or so) in my very first Bonneville excursion in which it broke the back off the motor, the trans and the differential as well as making the 6" driveshaft tunnel about a foot wide and took out seat belt mounts, all in spite of a driveshaft hoop. And that was less then 8000 rpm (but much longer shaft). (We fixed the whole mess and went on to set a record). I recognize your concern and calculators are just a guide line. As you are concerned talk to a good racing  shaft company and get their thoughts. Larger diameter can help as well-is there space?

[wheelrdealer]

Chris:

The one thing I forgot to check before Bonneville 2011 was the drive shaft. The car had been 176 many times on the 1 mile runways. I bought the original car from a guy that ran it at El Mirage one time. But after my 175 rookie pass I went for my "A" license. Upping the RPMs at 199 the drive shaft got real unhappy. Turns out, and I should have replaced the driveshaft, it was a stock spec driveshaft. Everything was fine until the 2 mile marker and 8,000 rpms. Needless to say it made a mess of things. Almost took out my seat belt mount. My advice go buy a race spec shaft that will take the RPMs you are turning.

Looking forward to see the Midget run.

My 2 cents


https://youtu.be/XUiM1-DfKYY

[PorkPie]

well, in my last runs for the records I shift from the first into second gear at 12.4k.....and the following shifts at 12.7k-12.8k....the engine survived my heavy foot....Stainless meant...don't get it in the 13k....at the World Finals the flashlight helped a lot as I could trust the light...I have only to be quick enough when the light showed up....saved some sweat not to check the rpm meter during the run...the neddle runs up so fast....

The 1 liter that Pork Pie set his record with was running 13.3 - 13.4 AFR...  Pentroof 4 valves like to be a bit leaner than the 2 valves that like that 12.2 range....
It sounds like the motor likes the revs, the limit is the valve train... if Mark thinks it has the spring to run 11 or 12K then you might want to go there... after you try 10K and hopefully set the record.  The 1K Porkpie used reved to 12.5K, I had Pork Pie shifting at 11.8K.  When we put it in BJ Burkdoll's truck we turned it up to 13.2 and shifted at 12.5.... It is still together...
Hey it's just a race motor... rev the piss out of it, that's where the HP is.

[PorkPie]

talking drive shaft....Ray's mishap at 135 mph during WoS..

[Milwaukee Midget]

Pork Pie - Bill -

I recall the photos Ray posted up of the carnage his driveshaft created under his Monte Carlo.

Both the Camaro and the Monte have live axles, and I believe that the GM style trailing arm suspensions tend to be better at keeping the pinion centered than leaf springs.

Granted, there's a lot more power on tap with the Chevy's than with the Midget, and the overall length is less than 2 feet.

But I mentioned the stock driveshaft to Tommy after we were done dynoing, and the look on his face was one of utter incredulity.

I'll see what I can come up with.

[wheelrdealer]

Pork Pie:

Great shot of Ray and his pretzel drive shaft. I miss RTR!

Chris, I was told my shaft probably failed because of the harmonics generated by high RPMs and balance.  The stock tube was .083 I think. The driveshaft builder stepped up the tube size but I cannot remember. I would have to look up the receipt to know for sure.

BR

[fordboy628]

Bob - Rex - I'm not nearly as worried about the engine as I am worried about this -

20210617_205234 by Chris Conrad, on Flickr

If this were a streamliner or a lakester where I did not have to worry about drivetrain compliance with respect to suspension travel, I'd lash it to a Hewland Mk-VII and be done with it.

But while it is short (23 1/2"), lightweight and recently serviced and balanced, I question the wisdom of 10K with a live axle on leaf springs.

The transmission has 17 passes on it at Bonneville after a rebuild with straight cut gears. I'm thinking of having a scraper tack welded to the inside cover to alleviate windage - especially seeing as it's likely I'll need to spend more time in the lower gears with higher input shaft revs.

Yeah, I know - I'm not running a mid-70's late model at Knoxville, and it's not going in a stern-drive speed boat. Even when the big boys rut the salt, it tends to be smoother than the alley behind my house - but I do think I need to proceed with some caution.

Talk it through - think it through . . .

It all comes back to Harold's quote - "Problems are almost always a sign of progress".

A thought on this:

Driveshafts DO NOT rotate @ engine RPM, UNTIL the internal trans gear ratio is 1 to 1 or higher, as in overdrives.

Driveshafts are solidly connected to a fixed gear ratio, IE: the diff ratio.    Hence driveshaft RPM is proportional to MPH/tire dia. / diff ratio.
(Look up the correct formula yourself, I'm busy calculating header dia  specs for the Mundelein Missile . . . . . .)

It is UNLIKELY that this driveshaft is ever going to see much over 10K RPM, UNLESS . . . . . you change diff ratio or tire dia
(Again, you do the math.  REMEMBER that 126.xxx MPH was set with the Tractor, current tire and 4.22 diff.  Back calculate the RPM for THAT, as a starting point.)
I get 8192.8 RPM off your chart for 127 MPH.     8386-8064=322*.4=128.8+8064=8192.8    135 MPH=8709 RPM, so . . . . judge accordingly.


Since I'm not ever going to drive the car, I could care less about what driveshaft you use.
BUT, having said all the above, I'd also say what driveshaft you use is a "de facto" judgment on the owner's intelligence.   Since a catastrophic driveshaft failure will no doubt severely damage or perhaps destroy the car, and its' then "occupant", you might want to "invest" in the best part available.

JMHO, but