Tapley data - looking for Berlina figure

davestebs · #1 (**permalink**) 05-14-2007, 08:24 PM

I've recenty discovered the Tapley data that is in the data tables in old road tests in Road & Track magazine. The numbers for total drag at 60mph in pounds force has peaked my curiousity. Numbers I have so far are: Giulietta Sprint: 73 lb, Sprint Speciale: 70 lb, Sprint GT: 105 lb, Giulia ti: 99 lb. Giulia spider: 130 lb, Sprint Zagato: 80 lb.

Does anyone have a R&T test for a Berlina? I'd like to know the number for that one. Just to humor an engineer...
Thanks!

Andrew · #2 (**permalink**) 05-15-2007, 07:08 AM

I have the R&T tests at home, but I'm not sure they were still getting Tapley data by then. I can look though.

Andrew

Andrew · #3 (**permalink**) 05-15-2007, 08:07 PM

As near as I can tell, R&T never did a full test of a Berlina, though they did some brief reports and I think one comparison, which I couldn't immediately find. But the Super test from early 1968 had no Tapley data, and though the TI test did from 1966ish. It showed:
5th gear: 10%
4th gear: 14%
3rd gear: 19%
2nd gear: 26%

This represents grade (slope), not pounds. So I don't know if you can compare this to the earlier data. It did show 99 lbs drag at 60 mph.

What is a Tapley meter and what does it measure?

Andrew

davestebs · #4 (**permalink**) 05-15-2007, 08:30 PM

Thanks Andrew,
Glenn's repair manual gives a brief decription of Tapley data. The figures are the maximum grade the car can climb in each gear. 100% grade is a 45 degree slope. The procedure for measuring drag is to accelerate to 80 mph on level ground, then coast down to 60 mph.

The thing that interested me was that the drag for a ti is less than the drag for a Sprint GT. We know that the ti has a low drag coefficient by design, but the actual drag is the coefficient times the frontal area times velocity cubed (I think, maybe it's velocity squared). Anyhow, I've wondered if the Sprint GT might have lower actual drag due to less frontal area, but it looks like the ti/Super still is better. I also wonder if the changes to the body of the Berlina resulted in more drag or less.

Sometime I want to do some research and find out how a Tapley meter works.

Damo105 · #5 (**permalink**) 05-16-2007, 01:49 AM

I remember reading somewhere that the drag on the 105 Giulia sedan series was lower than the coupes, and I think (could be wrong) it was the lowest drag of any Alfa up to that point. I also think it scored pretty well when measured against all cars at that time. Don't have any figures though. As the Berlina is bigger, and probably has a larger surface area at the front, I'd imagine its drag wasn't as good as the Super.

py105 · #6 (**permalink**) 05-16-2007, 02:23 AM

If anything the surfacing of the Berlina is a lot smoother which cuts down parasite drag. I would have to mildly disagree with Damo though, a Berlina has a front track of 52.1" compared to a TI's 51", so the difference is minimal.

If anything the way the Berlina's bonnet curves down to the grille aperture is preferable to the Giulia's messy facade. The sides, glasshouse, and Kamm-type tail on both are quite similar. This is all a little academic though, and probably not humouring our engineer friend very much.

Andrew · #7 (**permalink**) 05-16-2007, 06:37 AM

The Giulia body was proclaimed at the time to be one of the cleanest around, in spite of its looks, better than a Porsche 356 and I think second only to the Citroen DS.

Andrew

davestebs · #8 (**permalink**) 05-16-2007, 08:03 PM

No worries: I find some humor in persuing useless information.

I thought one of the areodynamic details of the Giulia is the way the front hood and sides fair into the grille area. I think there is a chance that the sharper edge of the sheetmetal around the grilie of the Berlina might increase drag. I wonder, if in the redesign, the style of the day was more important than areodynamics.

Yes, it is all academic, and don't get me wrong, I like both styles.

Green Berlina · #9 (**permalink**) 05-19-2007, 10:49 AM

Quote:

Originally Posted by Andrew

As near as I can tell, R&T never did a full test of a Berlina, though they did some brief reports and I think one comparison, which I couldn't immediately find. But the Super test from early 1968 had no Tapley data, and though the TI test did from 1966ish. It showed:
5th gear: 10%
4th gear: 14%
3rd gear: 19%
2nd gear: 26%

This represents grade (slope), not pounds. So I don't know if you can compare this to the earlier data. It did show 99 lbs drag at 60 mph.

What is a Tapley meter and what does it measure?

Andrew