Urba Centurion Update - (Kubota diesel, 100+ MPG in mixed driving - Fall 2012 on)

[nemo]

Nice thing about that transmission is you can use OD in third and fourth gears. IIRC should be about 500 RMP drop each gear change, 3rd, 3rd OD, 4th and 4th OD.

[changzuki]

Originally Posted by some_other_dave

Ugh, sorry to hear about the shipping troubles!! They can be a pain...

I know that the magazines have ads for swapping Toyota 5-speeds onto Triumphs. Might that be another option?

Oh, and I believe the overdrive was more properly the "Laycock De Normanville overdrive".

-soD

The Toyota 5 speed and the Ford 5 speed are both viable options, and pending the outcome of this may be on the table. The attraction with the "Laycock De Normanville overdrive" is to build on RQ Riley's original plans and team those with the 3.27 rear differential. The ability to have six-speeds when completed should compliment the small Kubota D850... ... Keyword = Should....
~CrazyJerry

[changzuki]

Originally Posted by Xist

Did you insure the shipment?

The seller did insure it but from the way I understood the process, it would've been quite some time before x,y,and z went through the channels. So, I've opted once again to be my own warranty and complaints dept... It makes for a more well-rounded person I'm told...
~CrazyJerry

[narclepticfool]

Sorry to hear about your shipping woes. A friend of mine shipped a mega computer with brown, and they turned it into an accordion. They're not the best.

This is going to be pretty sweet if you can get it worked out. With the extra gear and the OD, have you figured the new top speed? Think this is going to improve your MPG, or just give you a higher top speed?

[changzuki]

Originally Posted by narclepticfool

This is going to be pretty sweet if you can get it worked out. With the extra gear and the OD, have you figured the new top speed? Think this is going to improve your MPG, or just give you a higher top speed?

Excellent questions! I do have an rpm/speed chart based on the components being used... The calculations only do rpms in "x" increments or rpms for a given speed.
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Here is the breakdown:
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The "top speed" target is going to be exactly "88 miles per hour" because:
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http://www.youtube.com/watch?v=JFT7hNhop7w

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The big question will be the fuel economy boost or bust. I believe like any vehicle, that will depend on how it's driven. What I don't know will be the overall impact on fuel economy based on:
1) The extra weight of the larger 4-speed with Laycock overdrive
2) Any losses used to drive the pump in the Laycock overdrive

The stock three rail transmission is quite small and heavy for its size (but not heavy overall, maybe 35 pounds).
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It is shown below for reference:
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More to come of course!
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~CrazyJerry

[changzuki]

Originally Posted by nemo

Nice thing about that transmission is you can use OD in third and fourth gears. IIRC should be about 500 RMP drop each gear change, 3rd, 3rd OD, 4th and 4th OD.

Yes!!!!!
Upon completion we're going to revisit this post by nemo to see how the Kubota responds and what it means for the Centurion driving experience.
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~CrazyJerry

[redneck]

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Kubota Orange paint...???

Is that a hint of something to come...???



>

[changzuki]

Originally Posted by redneck

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Kubota Orange paint...???

Is that a hint of something to come...???



>

LoL! Redneck has been on-location so he may be "Back to the Future" with that...
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Let's just hope none of this get's too outta hand, including the orange paint. When this is over, I may not eat another peanut butter and jelly sandwich again! Ever!
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~CrazyJerry

[Xist]

Is anyone else in this situation?

Overdrive (mechanics)
An overdrive (OD) is a mechanism that allows an automobile to cruise at sustained speed with reduced engine RPM, leading to better fuel economy, lower noise, and lower wear.

Okay, I had already gathered most of that, although lower wear is a nice bonus.

In the era of front-engine, rear-wheel drive layouts, the device for achieving an overdrive transmission was usually a small separate gearbox, attached to the rear of the main gearbox and controlled by its own shift lever or electrical actuation button. These were often an optional extra on some models of the same car. As popular cars became faster relative to legal limits and fuel costs became more important, particularly after the 1973 oil crisis, the use of 5-speed gearboxes became more common in mass-market cars, with the 5th gear being an overdrive, eliminating the need for a separate gearbox.

Regarding the Laycock overdrive:

The system features an oil pressure operated device attached to the back of the standard gearbox operating on the gearbox output shaft. Through a system of oil pressure, solenoids and pistons, the overdrive would drop the revs on whatever gears it was used on by 22% (.778). For instance, the overdrive system applied to a Triumph TR5 operates on 2nd, 3rd and top gear. When engaged, the overdrive would drop the revs from 3000 by 666 RPM, or from 3500 the drop would be 777 RPM to 2723 net. The advantages this reduced rpm had on fuel consumption was most often quite near 22% decrease during highway driving.

http://en.wikipedia.org/wiki/Overdrive_(mechanics)

So, the overdrive is an external taller fifth gear?

[changzuki]

Originally Posted by Xist

Is anyone else in this situation?




Okay, I had already gathered most of that, although lower wear is a nice bonus.



Regarding the Laycock overdrive:

http://en.wikipedia.org/wiki/Overdrive_(mechanics)

So, the overdrive is an external taller fifth gear?

I like to think of it as being similar to the 2 speed rear ends on the big trucks. A true 5th gear overdrive is just that - one more gear. This overdrive is an add-on to the regular transmission. You could get a straight 4 speed or the optionally added on overdrive unit mounted on the rear of the manual transmission. It has the ability to be engaged within the normal 1-4 gears, specifically as you've mentioned (and in this case) it can be engaged in 3rd and 4th. So in essence it will provide two additional distinct ratios beyond the 1,2,3,4 gears (add in 3rd overdrive, and 4th overdrive.) A nice patch between the 3rd to 4th hop, and then the overdrive beyond 4th. It also shares oil from the main transmission so you'll see some discussion on that topic across the net too. It's an interesting unit for sure and lots of vehicles did use them. An up-to-date unit is found under the "Gear Vendors" brand. An "all gear" lever operated version of an overdrive was the Hone-O-Drive (from the 60's and 70's) that could be added on within the driveline if one wanted overdrive in their vehicle. Apparently those are back now too!

~CrazyJerry