Australian Belly Tank

[Stainless1]

Finally... Someone added a little humor back into this thread.   
Looks like the task of getting that motor in that tank is going to cause you a few hard nights.  Some folks think this stuff is easy... mostly guys with doors I think....

[grumm441]

Easy
Sure
G

[Speed Limit 1000]

Easy? What fun would that be

[grumm441]

[Speed Limit 1000]

Just a few weeks work and you will be ready to run

[Dr Goggles]

OK holiday makers.

If you had to choose two gears, or hang on, you could have two gears and you could choose one of them (the other one would be 1:1) and you had a motor ( ok, an engine) that could make 500hp at full whack but about 3hp under 2000rpm what would they be?

here's some sums ( for a driveline that ends with 28 inch tyres)....

I have made a few assumptions here.
1./ That my 302 F100 can push the tank to 50mph
2./ That the 2nd/3rd gear change with a 2ft long gear shift in the truck won't induce a fatal whiplash injury in the driver of the tank.
3./ That the push period 1st/2nd gear change happens before the first set of clocks thus allowing the tank to remain eligible for the long track.


RPM                      Transmission ratio.                   Final Drive                Speed (mph)

2000                              1.38                                    2.41                          50

2200                              1.52                                    2.41                          50

8000                              2                                         2.41                         138

4002                              1                                         2.41                         138


2125                             1.38                                     2.56                          50

8000                             1.38                                     2.56                          188

5792                             1                                          2.56                          188             

2341                             1.52                                      2.56                         50

8000                             1.52                                      2.56                         171

5268                             1                                           2.56                         171

[SPARKY]

My take:                        TR                                       RA                       FDR                           MPH

RPM                      Transmission ratio.     Rear axle ratio                    Final Drive                Speed (mph)

2000                              1.38                                    2.41                     3.33                            50

2200                              1.52                                    2.41                     3.67                            50

8000                              2                                         2.41                                                      138

4002                              1                                         2.41                     2.41                          138


2125                             1.38                                     2.56                      3.54                            50

8000                             1.38                                     2.56                      3.54                           188

5792                             1                                          2.56                      2.56                           188             

2341                             1.52                                      2.56                      3.54                            50

8000                             1.52                                      2.56                     ??                           171

5268                             1                                           2.56                      2.56                           171

[Dr Goggles]

OK.

So you got me on a point of order. "Rear axle ratio"

What I was trying to highlight was how low the motor would be turning on a 50mph push off, and what the split would be at the gear change.

I'm not sure what ratios are available in the Bert because I've been too lazy to look.

For the record I like the look of 2.56/1.52

I thought we had a 2.73:1 somewhere, but alas.

[tauruck]

Awesome, guys.
I only wish you all the best.

[fordboy628]

OK holiday makers.

If you had to choose two gears, or hang on, you could have two gears and you could choose one of them (the other one would be 1:1) and you had a motor ( ok, an engine) that could make 500hp at full whack but about 3hp under 2000rpm what would they be?

here's some sums ( for a driveline that ends with 28 inch tyres)....

I have made a few assumptions here.
1./ That my 302 F100 can push the tank to 50mph
2./ That the 2nd/3rd gear change with a 2ft long gear shift in the truck won't induce a fatal whiplash injury in the driver of the tank.
3./ That the push period 1st/2nd gear change happens before the first set of clocks thus allowing the tank to remain eligible for the long track.


RPM                      Transmission ratio.                   Final Drive                Speed (mph)

2000                              1.38                                    2.41                          50

2200                              1.52                                    2.41                          50

8000                              2                                         2.41                         138

4002                              1                                         2.41                         138


2125                             1.38                                     2.56                          50

8000                             1.38                                     2.56                          188

5792                             1                                          2.56                          188              

2341                             1.52                                      2.56                         50

8000                             1.52                                      2.56                         171

5268                             1                                           2.56                         171

Right about NOW would be a good time to know the rpm where peak bhp and peak torque are at.    Figure that the engine will pull clean to about 500 rpm over the power peak.   Assuming it is reliable to that unknown rpm.    Most N/A engines start to pull well at about 500 to 1000 rpm under peak torque.    But this is all very generalized.

It appears that you need somewhere around 3200 to 3800 rpm in the "power band" to use these example gears.    For N/A full race engines, the spread between peak tq and peak bhp varies from about 1500 rpm to 1800 rpm or so.   In my world, a wider power band would indicate a less than "full race" spec.   If you add 500 rpm to the top and 800 rpm to the bottom, that gives a 3100 rpm range, a bit on the tight side of what appears to be required.    My SWAG is purposefully conservative.

If your shift to a 1-1 top drops you to a bhp level below what is required to accelerate the tank, game over, as you well know.    I'm thinking you blokes need more gears, say 4, with progressive spacing (rpm drops) as you go up the gears.

I'd model something like:
1st    1.85
2nd   1.45   28%
3rd    1.18   23%
Top   1.00   18%

To start I'd use a diff ratio that gives a reasonable target speed right at peak bhp rpm.    With the ability to pull 500 rpm over (presumably) you would get a speed bonus up to the point you hit the "aero wall".

The worst case scenario requires ~ a 4000 rpm power band, which is really wide.

To use a "Sconnie Nation" phrase, a favorite of your buddy the "MM", you are on the road to slicing the cheese "really thin".   Some real numbers to eliminate the "SWAGS" is what is in order here.    Write an Excel spreadsheet to analyze this, or, spend the 50 bucks on Performance Trend's Transmission Gear Calculator V2.0

http://performancetrends.com/tg.htm

And no whingeing about the 50.   You guys drink that on a weekend . . . . .  

 

[Interested Observer]

The attached worksheet has a graph of estimated gearing and drag predictions for the SoS.  Of course, gearing should be chosen as the result of examination of actual power curves and realistic drag results. 

In this case, the power curve starts with the stated 500 hp at 8000 rpm, has an intermediate point from Kenny’s dyno run of 420 hp at 6400 rpm, and a completely WAG of 80 hp at 2000 rpm.  Other input data are stated in the graph title.  All of this can be easily revised if realistic information were to become available.

I would say, based on what is here, that the 1.52 ratio is a non-starter.  The 2.56 final drive ratio simply shifts the power curves slightly to the left.

[kiwi belly tank]

Gogg's & Grumm, why are you trying to limit yourself to two speeds?? 
  Sid.

[Dr Goggles]

Gogg's & Grumm, why are you trying to limit yourself to two speeds?? 
  Sid.

Just tossing the salad on using a Bert box.

The trans ratios I offered up were hypothetical. My suspicions are the same as those voiced here. I watched The Reverend miss a gear and I had to use 3rd myself from about 60mph at one stage with our last motor and short of going to a 3.08 I can't see any gear combinations that will keep the motor anywhere near peak power WHEREVER that is. (see how I've adopted the popular new technique of capitalizing the important word in the new post stupid environment).

Yes FordBoy, thats what I'm talkin about, our current box has a 1.32 and that is in my less than than humble but freely available opinion TOO LOW.....

This all may not be so urgent because a gully-washer just hit Gairdner.

[Dr Goggles]

The attached worksheet has a graph of estimated gearing and drag predictions for the SoS.  Of course, gearing should be chosen as the result of examination of actual power curves and realistic drag results. 

In this case, the power curve starts with the stated 500 hp at 8000 rpm, has an intermediate point from Kenny’s dyno run of 420 hp at 6400 rpm, and a completely WAG of 80 hp at 2000 rpm.  Other input data are stated in the graph title.  All of this can be easily revised if realistic information were to become available.

I would say, based on what is here, that the 1.52 ratio is a non-starter.  The 2.56 final drive ratio simply shifts the power curves slightly to the left.

Is this based on us running 215 (6450rpm) with 330hp (using 2.41:1) and hitting the wall with the 2.14:1 at 5300rpm (estimated 270hp)?.... I don't have it at hand but the spreadsheet result I seem to remember had a slightly steeper curve  indicating we needed around 420-440hp at 240mph.......

I don't want to be biding my time with 80hp, we only have seven miles........

[Interested Observer]

Sorry, I thought this was about at least a three-speed with alternate 2nd ratios.  If only two-speed, the 1.52 looks more suitable as a possibility.

And, again, this is all academic (and possibly pointless) until there is a valid power curve available.  Get that lump and the Electromotive guy down to the dyno!

The only firm data I had was Kenny’s dyno number.  Everything else was just guessing.  Given the above actual performance figures, I’ll try working them into the mix.