Thread: 6BD1T in Land Rover?

Originally Posted by zkdaz

Thinking about it, I would expect Ashcroft to rate the LT230 very conservatively as they offer some warranty on their rebuilds. Good to know others have pushed it further without problems, full time 4wd and coils are kind of the soul of a Land Rover.

Fully agree, drive line stress is limited by traction providing back torque (rather than engines available torque), which is a function of weight and grip. Bigger tyres, even if you adjust the diff ratio for gearing, have more grip therefore you can apply more torque before they let go.

Bush65, inertia is mass by velocity not acceleration, torque is mass by acceleration, but your logic still holds. Highest loads will be impact loading when traction suddenly increases back torque, ie the tyre grabs something. These impact loads will be lower if there is less momentum in the system to dissipate, so best practice is to drive as slowly (linear inertia) at low revs (angular momentum) as possible when traction could suddenly increase. There are however times when we need high inertia/momentum to carry us past a patch of low traction, this is when we have the highest risk of damage.

To my mind, a well designed vehicle should stall when traction exceeds engine torque, rather than break something. And if this is not possible the weakest part should be the easiest to change, ie the spline caps on a full float axle hub. This logic of weak engines and soft metal was classic british post war vehicle design.

Now if I run 35" tyres with chunky grip, an engine with gobs of low down torque that won't stall and load her up with a few weeks of supplies, have I exceeded the strength of the drive line? Anecdotal evidence in these forums suggests this sort of combination will eat any gearbox weaker than an LT95, followed by cv joints, half shafts and flex rover crown wheels.

I am nearly ready to buy a vehicle and start slowly doing it up but I want to be absolutely clear in my mind what I am aiming for at the end. Just to make my decision more difficult, there is a high potential I will move to NZ at some point during or after the build, so I need to meet australian and NZ rules.

I am currently leaning towards buying a factory isuzu 110, sorting out the axles, diffs, suspension, body, etc. Then hunting down a complete truck turbo motor and gearbox, rebuilding the original block using the truck and new parts (thus keeping the factory engine and chassis numbers in case NZ makes it harder to import modified vehicles) and use the truck clutch and gearbox with the LT230 adaptor.

Undecided are the axles, dana 60 sound about right but I need to do more reading, and the flywheel housing / starter motor depending on what the heaviest available flywheel is compatible with, preference for 24v and don't want to notch the chassis.

I have no problem sinking lots of time and money in to this project, I am hoping it will last forever, but I do want to avoid costly mistakes.

Thank you all so much for your input, it is really helpful being able to bounce ideas around with people who have actually done similar stuff already. I promise when I do decide and find a good base vehicle to take lots of photos as I go.

Cheers
Dan

I designed the input adapter shaft for my LT230 to take ~2000Nm. This was back calculated as worst case through my vehicle from maximum traction (at my 29" tyres) through diff gearing and high ratio transfer gears.

If you then want to translate that to gearbox and engine torque, you can consider 667Nm engine at 3:1 gearbox reduction (2nd gear in my MSA box). Higher gears mean more engine torque is required.
As you can see. There are very few situations where you are putting this much torque through. The gearbox and clutch also filter out a certain amount more vibration.

If you want more flywheel inertia, just add thickness and move everything before you start the conversion.

NZ conversion rules (LVV Cert) are easy. Your conversion gets checked over by a certifying mechanic (yes, no engineers involved) and the vehicle is put through the standard WOF procedure. If all good then it's plated with the modification details and off you go. The only recent change is a driveshaft safety loop on all turbocharged modifications.
We have no emissions requirements for conversions. However we do for imports. You would need to provide proof of ownership for a certain time period before import. I don't have those details.

Originally Posted by zkdaz

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Bush65, inertia is mass by velocity not acceleration, torque is mass by acceleration, ...

It would take a pretty good mind to find gross flaws such as that in Newton's work ...

Originally Posted by zkdaz

Please don't take it the wrong way, I have immense respect for all you guys experience and knowledge. I just had to do a double take and read it again because of the choice of words, not the concept he was explaining. We can't discuss ideas if we each use words to mean different things. Not trying to teach anyone to suck eggs.

Dan

Edit: Mass x velocity is momentum, not inertia. Mass x acceleration is inertia, not torque. Torque is force x radius.

The following are extracts pasted from Wikipedia. Note that change in velocity (motion) is acceleration.

Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by applied forces. Inertia comes from the Latin word, iners, meaning idle, or lazy. Isaac Newton defined inertia as his first law in his Philosophiæ Naturalis Principia Mathematica, which states:[1]

The vis insita, or innate force of matter, is a power of resisting by which every body, as much as in it lies, endeavours to preserve its present state, whether it be of rest or of moving uniformly forward in a straight line.

In common usage the term "inertia" may refer to an object's "amount of resistance to change in velocity" (which is quantified by its mass), or sometimes to its momentum, depending on the context. The term "inertia" is more properly understood as shorthand for "the principle of inertia" as described by Newton in his First Law of Motion; that an object not subject to any net external force moves at a constant velocity. Thus an object will continue moving at its current velocity until some force causes its speed or direction to change.
....
Interpretations

Mass and inertia

Physics and mathematics appear to be less inclined to use the popular concept of inertia as "a tendency to maintain momentum" and instead favor the mathematically useful definition of inertia as the measure of a body's resistance to changes in velocity or simply a body's inertial mass.
This was clear in the beginning of the 20th century, when the theory of relativity was not yet created. Mass, m, denoted something like an amount of substance or quantity of matter. And at the same time mass was the quantitative measure of inertia of a body.
The mass of a body determines the momentum of the body at given velocity ; it is a proportionality factor in the formula:
The factor m is referred to as inertial mass.
But mass, as related to the 'inertia' of a body, can also be defined by the formula:
Here, F is force, m is mass, and a is acceleration.
By this formula, the greater its mass, the less a body accelerates under given force. Masses defined by formula (1) and (2) are equal because formula (2) is a consequence of formula (1) if mass does not depend on time and velocity. Thus, "mass is the quantitative or numerical measure of body’s inertia, that is of its resistance to being accelerated".
This meaning of a body's inertia therefore is altered from the popular meaning as "a tendency to maintain momentum" to a description of the measure of how difficult it is to change the velocity of a body. But it is consistent with the fact that motion in one reference frame can disappear in another, so it is the change in velocity that is important.
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Originally Posted by isuzurover

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Torque ratings for gearboxes and t-cases are somewhat of a misnomer.

...

AGMA (American Gear Manufactures Association), have a large number of Gear Standards, but I'm only familiar with one - I don't have my copy with me at this moment, and I haven't used it for many years, so can't quote the precise number or title, but it is something like Rating Spur and Helical Gears.

This was the standard used around the world for designing these type of gears, but was replaced by the ISO standard when it was introduced - AGMA was the secretariat for the ISO committee that developed this particular standard. The ISO standard was being developed at a time when I had occasional gear design so I kept an eye on what was happening. By all accounts it is a very complex standard intended to be implemented through third party computer programs, i.e. beyond any hope of anyone with a scientific calculator.

Even with the old AGMA standard, for determining the geometry factors 'I' and 'J' I used software that was developed by some BHP engineers (which became an Australian Standard). Those two factors would otherwise consume a lot of time.

As I said, AGMA have a lot of standards, and they probably would have included one for automotive gearboxes.

If there is no specific standard for rating the gears in an automotive gearbox or transfer case, there is no reason why the one for spur and helical gears couldn't be used.

With the rating standard I'm familiar with, common practice is to rate gears in terms of power, as that is generally more useful, but torque could be used as alternative. There are two ratings, 'strength' and 'wear' (both need to be determined and apply to a life of 12000 (or should that be 24000?) hours, whichever is least.

In a gearbox, every pair of gears need to be checked and so should the shafts and bearings. So it is not a trivial exercise to rate an LT230, and you before you could start calculating, you would have to determine a great deal of data for each gear that include tooth details, material and hear treatment (hardness), manufacturing tolerances on cutting precision (gear quality number), lubrication, gear alignment tolerances, etc.

Originally Posted by isuzurover

There are a few out there...
6BT 109 Land-Rover - YouTube

Hey,
that's Brutus, it belongs to my mate JL and actually is not a Stage One but an ex-military SIII with some Defender panels.

I drove it in Moab a few years ago, and it's in pieces nowadays, waiting for rebuild and some improvements

You can find a specs list on my site:
Whitedog Rover, Brutus the 109"...

Just out of curiosity, how would a fairly standard 6x6 perentie driveline stand up to a 6bd1-t?
It has TRB LT95 & 4.7 r&ps. Will be swapping out centers for lockers.
Seeing as I am engineless at the moment, and the truck is very heavy, it might be a good option. Thinking more in terms of pulling up some big hills and overtaking rather that rock crawling.

Originally Posted by Jitterbug

Just out of curiosity, how would a fairly standard 6x6 perentie driveline stand up to a 6bd1-t?
It has TRB LT95 & 4.7 r&ps. Will be swapping out centers for lockers.
Seeing as I am engineless at the moment, and the truck is very heavy, it might be a good option. Thinking more in terms of pulling up some big hills and overtaking rather that rock crawling.

You would want to swap to 3.54s and a 0.996 t-case.

Originally Posted by isuzurover

You would want to swap to 3.54s and a 0.996 t-case.

Unless it's been modified it will have the .996 transfer ratio. And yes the driveline should stand up to the 6BD1 as long as you are not a revhead.

I drove an army sixby around last weekend, and 80km/h is the top useful speed. Managed to hit 100 on a downhill, but foot to the floor it wouldn't hold that speed up the slightest of rises.
4.11 diffs or thereabouts with 255/85/16 tyres would be my pick for useful gear ratios-would get cruising speed around 100. A bit more through the turbo would help too.
Go for too tall a final drive ratio and 1st high might be a problem.
The 4BD1T didn't do too bad but we weren't heavily loaded, just troop seats and gear cages. They weigh a fair bit empty anyway!