Thread: Maxi drive reduction gears

Originally Posted by rick130

You already have a 49% lower low range, ya greedy bugger

well with only 17hp and 4nm, you can never have to many gears.....

Originally Posted by djam1

Bill wouldn't the permanent engagement of the gears just generate heat this is one reason I have never been game to use the Rocky Mountain overdrive?

No, only if they rotated in relation to each other, not when locked together

Originally Posted by uninformed

well with only 17hp and 4nm, you can never have to many gears.....

You're too young to remember, but as a kid I remember being stuck behind old smelly, belching Pommy POS trucks like Fodens and Leylands on the hills of the Putty Rd when we were going on holidays and they seemed to have a million gears to go along with their top speed on the flat of 72km/h, which would indicate they only possessed around 15HP being NA engines, so I take your point........

Originally Posted by djam1

Bill wouldn't the permanent engagement of the gears just generate heat this is one reason I have never been game to use the Rocky Mountain overdrive?

I believe there was a thread on these forums concerning the amount of heat that the RM overdrive generates in our generally hotter conditions when compared to Canada.I haven't checked the thread for some time but I think synthetic lube was found to be the solution to keeping the overdrive alive.
The centre seat panel of my truck gets almost hot enough to have a good egg, bacon and lamb chop fry up when I use my crawler in low, but temps are reasonable in direct drive,and unlike an overdrive the crawler is only used at low speeds for relatively short distances.

Serg the Nissan doubler would give you the choice of high/high high/low low/high and low/low. the standard nissan low range is not as low as the Ashcroft crawler, but aftermarket gearsets are available I believe.
Bill.

Originally Posted by rick130

You're too young to remember, but as a kid I remember being stuck behind old smelly, belching Pommy POS trucks like Fodens and Leylands on the hills of the Putty Rd when we were going on holidays and they seemed to have a million gears to go along with their top speed on the flat of 72km/h, which would indicate they only possessed around 15HP being NA engines, so I take your point........

OT but tenuously related to the subject.
The old Fodens were, at least from a tractive effort perspective, the most powerful road train spec prime mover of their day. The 150BHP Gardiner engined rigs had a 6 speed main gearbox plus 3 speed planetary geared auxiliary box. With the drive flanged axles fitted to the hubs they had a maximum speed of 30mph and a nominal gross train weight of 45 tons. If the operator was offered an extra payload and was prepared to travel more slowly, an alternative set of halfshafts were carried and could be fitted . Instead of having drive flanges, these halfshafts had a sun gear on the end that engaged with planetary gears already inside the hubs to give a further 2:1 reduction. The result was a gross combination weight capability of 90 tons with a maximum speed of 15mph.Roads were pretty crook in the NT outback in those days, so 15mph wasn't as slow as one might think with a couple of stock trailers snaking along behind.
I don't know how anyone could drive them in the heat of the NT though. They were a cab over engined truck and the engine sat snuggly beside the driver.
Bill.

Bill,we are harder up here,my Acco or the Iveco cab over I was in yeasterday get hot enough to burn steak on the floors but we aren't latte sippin' tree huggin' fairies like them city drivers!!!. Pat

Originally Posted by PAT303

Bill,we are harder up here,my Acco or the Iveco cab over I was in yeasterday get hot enough to burn steak on the floors but we aren't latte sippin' tree huggin' fairies like them city drivers!!!. Pat

Pat, I'd reckon the Iveco with several hundred horsepower, aircon and power operated everything, cruising effortlessly at 100kph on improved roads would be a far cry from the old Foden dragging 90 tons on rough sand tracks, struggling along flat out at 1900rpm with no air, no steer, and at 25kph, no end in sight..
The drivers in those days were hard men alright. I dips me lid to them.
Bill.

Originally Posted by wagoo

Thanks for the explaination Mox. Just as purely a mental exercise I'm now thinking again about Sergs suggestion for a 3 spd transfer case. With your modified arrangement, the centre gear of the intermediate cluster becomes redundent. If the intermediat gear were made into a 3 piece unit similar to an LT95,and that redundant helical gear were to be replaced with a spur gear come dog clutch, then a mating spur gear could possibly be mounted on splines machined on the hub in front of your new 22 tooth helical gear.This spur gear set would need to be of a lower ratio than your 22/44 tooth gear set, otherwise it would be quite silly and impractical, because high and low range would be relatively quiet helical gears whilst the additional intermediate range would be noisey spur gears.
Bill.

I have the advantage of being able to look at this box partly assembled to get things in perspective. Actually would much prefer I couldn't - with it installed in vehicle. The suggestion of a third lower range is not on. The 41 tooth middle gear on the cluster is about as big as can clear the collar where the selecter fork goes on the output shaft and bigger would be needed. Also, would not want to go too much smaller than the 22 tooth on the input shaft. Then the problem of somehow fitting in an additional selector mechanism.