Aeromodding in the 1930's: 38 mpg, 70 mph Model T

[roverdriver]

Interesting article.

It was a frequent practice in Australia and New Zealand, when the T was an everyday car, to fit a Chev. 4 gearbox after the standard T's epicyclic transmission. The result was, as stated 7 forward gears and 5 reverse, however as the T transmission in 'high' was 1:1 and the Chev. gearbox in top is 1:1, there is no overdrive effect so no increase in top speed. The reason for the conversion was usually because the vehicle was used in hilly country with heavy loads, and a second hand Chev gearbox was cheaper than a Ruxstell axle.

There is no mention of alterations to the engine so how was the higher speed managed? Several OHV conversion kits were available for the T, and one of those could have created the extra pace.

Many years ago I drove Model T's extensively. Usual fuel consumption was in the region of 25 mpg but that was imperial gallons at four and a half liters to the gallon, a U.S. gallon is 3.8 liters.

It is interesting that the new body is so high over the engine compartment, one would think that a gentle rise from the top of the radiator to the bottom of the windscreen would have been more aerodynamic.

Certainly a very interesting 'dress-up' for a T, I would have enjoyed studying it.

Roverdriver in Australia.

[moTthediesel]

That's a very cool T!

Just a thought -- could the second transmission have been mounted backwards? That would give a 1/1 in forth and then 3 more possible overdrive ratios, no?

[Christ]

Would it be any different to split the first transmission's gears, rather than splitting the rear transmission's gears?

In other words, first transmission, first gear, rear transmission, 4th, 3rd, 2nd, 1st, first trans in 2nd gear, rear trans in 4th, 3rd, 2nd, 1st....

Or, Rear trans in 4th, first trans in 1st, 2nd, 3rd, 4th, rear trans in 3rd, front in 1st, 2nd, 3rd, 4th....

Would give the user 16 selectable gear ranges! LIKE A BIG TRUCK! LOL.

[thatguitarguy]

Awesome finds guys! This is really interesting and fun!

[roverdriver]

The T transmission is a two speed one. It is epicyclic, just like many later automatics. A Chev of the period was a three-speed sliding gearbox. Possible gear combinations would be- low plus 1, 2, 3, high plus 1, 2, 3, then reverse/reverse giving a very slow forward, so seven forward gears. To travel backwards, the choices would be T.reverse plus 1, 2, 3 or Chev reverse plus T low or high giving 5 backward direction gears.

As far as mounting the Chev gearbox backwards, I am not sure how practical that would be, but high and top (3rd.) would still only be 1:1 plus 1:1. High and 2nd would certainly act as an overdrive, but I wonder if the gearbox would handle the thrusts created. High and 1st would give an even greater overdrive. It would still give 7 forwards and 5 reverses.

To move off, one would have to select low/3, the next gear would be high/3, and so far all would be the same as a standard T. Next change would have to be high/2, and then high/1 if both engine and gearbox can manage that.

The intermediate low/2 and low/1 would not be practical to use in a progression of gear changes because of the way the epicyclic transmission functions.

Upward gear changes should work all right, but downward ones (no matter if the Chev box is right or wrong way round) are extremely difficult. In my experience, because the T clutch does not positively disengage, especially when the engine oil is cool and therefore thicker, a double declutch action is almost impossible, and of course the Chev box has no synchromesh so double declutching is almost essential to down change with it.

The T engine does have amazing torque so it is feasable that it just might handle the backward mounted Chev gearbox. As I have said, I have seen (and driven) T's with a Chev box fitted, but never with the Chev box back to front.

Roverdriver in Australia.

[Christ]

I've seen other setups that were done similarly, just wondered (without reading, shame on me) how it was worked out in this case.

I instantly assumed (shame again) that both transmissions were identical.

[roverdriver]

Quite understandable, Christ. Unless you have owned/driven a T and/or a Chev 4 then you would have no way of knowing.

One of the advantages of the T over its rivals in its early days, was the fact that the transmission was designed so that there was no gear lever and awkward clutch and lever gear changes to manipulate. That helped its popularity. As motoring became more universal, drivers became used to a sliding gearbox so eventually the T's epicyclic one was looked at as a disadvantage. When the 'stop gap' car, the Model A was designed it had a conventional 3 speed sliding gearbox, it did however retain a multi-plate clutch albeit a dry one unlike the T which ran in an oil bath. By 1929 the multiplate gave way to a modern-style single plate one.

If you ever get an opportunity, study and drive a T. You will find it an amazing experience.

Roverdriver.

[Christ]

The only thing I've driven that was close was a T bucket roadster... it had a 427 in it with a 4 speed manual. I couldn't keep my foot out of it long enough to appreciate any other part of the car.

[MetroMPG]

Originally Posted by roverdriver

There is no mention of alterations to the engine so how was the higher speed managed?

The speed increase would have come from the reduced aerodynamic drag, presumably.

[roverdriver]

If you look at the frontal area of the streamlined version, and compare it with the standard T, I am sure that you would find that there is little, if any, difference. The streamlined car does not have any surfaces at right angles to the direction of travel, but the very front (radiator area) is much higher than a standard car. I agree that the rear would have less drag.

That kind of increase in speed could not be created purely from improved aerodynamics- don't forget that streamlining only helps after about 60 mph anyway.

A back-to-front Chev gearbox might account for some of the speed as it could act as an overdrive, but you must consider that a T engine is rated at 22hp, has a low compression and cast iron pistons. Converting to OHV and fitting aluminium pistons while also increasing the compression will easily achieve 70 mph even without a streamlined body and with standard transmission and final drive.

I have driven a Model T with the engine converted as above, and with a standard chassis and body. When I got to about 70mph. (the speedo only went to 60) I decided that I would prefer to keep on living, so decelerated rapidly down to a sedate 45 mph at which the car was quite manageable.

Roverdriver in Oz