Giles' misc. Work bench.
- Thread starter Giles
- Start date
Tim Watson
Western Thunderer
I nearly demolished a Turdis toilet at a rally with my miniature traction engine when the diff seized and steering was lost...
Tim
Tim
Phil O
Western Thunderer
Tim Watson
Western Thunderer
Sorry Giles. Looks like I started a bit of thread drift...
Tim
Tim
Osgood
Western Thunderer
If I recall correctly Giles, you have been driving only one wheel on a drive axle - the other is floating in order to facilitate turning?
Is this double axle set-up the same?
Difficult to tell from the video.
So if both driven wheels are on the same side, the reluctance to turn is an issue of dragging two axles round a curve, or two interconnected wheels one behind the other off a straight line - not the absence of a differential?
If driven wheels were on opposite sides it would certainly behave like a single axle with wheels fixed - i.e. no diff.
I thought for a moment you had been 'doing donuts' with the AEC until I realised the circles on your worktop were probably made by coffee mugs.....
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simond
Western Thunderer
If you were to power both wheels on one axle, and only one on the other, and arrange that the first were not in intimate contact with the ground (fag papers...) then it would steer as a 4x1, like the traction engine and others, but the illusion of the other driven axle would be maintained.
alternatively, leave one axle undriven and floating so it gets dragged along, and turns. Saves pinions.
Atb
Simon
alternatively, leave one axle undriven and floating so it gets dragged along, and turns. Saves pinions.
Atb
Simon
Giles
Western Thunderer
The very first lorry I made drive only one wheel in anticipation of the problem - but I soon found that it was a little light-footed and prone to slipping, so I very quickly glued up that bearing to make it a solid fixed axle, whereupon everything worked perfectly.
The only vehicle which broke this rule was the traction engine, which with a fixed axle only goes straight! This then had a bearing inserted in one wheel, do it is single wheel drive (like a real one with the pin out!) . Future ones will have a diff.
This 6 x 4 has two fixed axles, and works because there is more weight on one than the other, so the rear axle is barely touching the ground- but go over a bump or kerb and it will come into its own!
When I did my HGV training, we had a Class 2 (I was doing Class 1) which was a 6 x 2 TK which frequently ended up with it's driving axle in mid air, spinning away....
This has been about finding the problems, and has proved interesting and encouraging, although if axles were sprung, it would be a different matter.....
The only vehicle which broke this rule was the traction engine, which with a fixed axle only goes straight! This then had a bearing inserted in one wheel, do it is single wheel drive (like a real one with the pin out!) . Future ones will have a diff.
This 6 x 4 has two fixed axles, and works because there is more weight on one than the other, so the rear axle is barely touching the ground- but go over a bump or kerb and it will come into its own!
When I did my HGV training, we had a Class 2 (I was doing Class 1) which was a 6 x 2 TK which frequently ended up with it's driving axle in mid air, spinning away....
This has been about finding the problems, and has proved interesting and encouraging, although if axles were sprung, it would be a different matter.....
Osgood
Western Thunderer
With a 4 spring setup like that AEC the spring ends between axles are usually on a rocking hangar so when one axle drops down the other goes up to maintain ride height - also gives a bit more axle movement.
Others (especially on trucks that might venture off the black top) have a 2 spring rocking bogie with a centre pivot which gives quite remarkable axle travel and which would be straightforward to recreate - just like a pair of compensated loco axles on an 0-6-0.
With some revision to your added axle mounting plates the AEC would make a good testbed - it might possibly eliminate much of the turning issues.
I took a newly acquired (pre-loved) 2 spring bogie tipper from rural East Anglia over to rural South Wales to collect an old McLaren 5 cyl engine.
It was my first vehicle with two rear axles let alone diff locks.
The very last very tight turn in the middle of a village was up into a very steep hill, and that is where all forward progress abruptly stopped.
Rather than thinking 'why', I put my head in my hands at the thought that I'd broken down as far away from home as was possible.
It then slowly dawned on me that such was the change in gradient the front drive axle was hanging in mid air - it had even beaten the 2-spring bogie!
Problem solved at the flick of a switch - the inter-axle diff lock. Doh!
In my defence this was only the truck's 2nd outing and the first to encounter a proper hill.
Taking the turn loaded at the bottom of the hill with a high centre of gravity was a bit heart stopping!
Oh heck, yet another thread drift - sorry!
Others (especially on trucks that might venture off the black top) have a 2 spring rocking bogie with a centre pivot which gives quite remarkable axle travel and which would be straightforward to recreate - just like a pair of compensated loco axles on an 0-6-0.
With some revision to your added axle mounting plates the AEC would make a good testbed - it might possibly eliminate much of the turning issues.
I took a newly acquired (pre-loved) 2 spring bogie tipper from rural East Anglia over to rural South Wales to collect an old McLaren 5 cyl engine.
It was my first vehicle with two rear axles let alone diff locks.
The very last very tight turn in the middle of a village was up into a very steep hill, and that is where all forward progress abruptly stopped.
Rather than thinking 'why', I put my head in my hands at the thought that I'd broken down as far away from home as was possible.
It then slowly dawned on me that such was the change in gradient the front drive axle was hanging in mid air - it had even beaten the 2-spring bogie!
Problem solved at the flick of a switch - the inter-axle diff lock. Doh!
In my defence this was only the truck's 2nd outing and the first to encounter a proper hill.
Taking the turn loaded at the bottom of the hill with a high centre of gravity was a bit heart stopping!
Oh heck, yet another thread drift - sorry!
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Giles
Western Thunderer
Using bevel gears, of course I had to keep both axles under strict controls ! One could produce a 'bogey' which rocked fore and aft, and possibly even one where the back axle swivelled, but I shouldn't like to try it in 4mm myself.... and then of course, without diffs, were back into the steering issue!
That really does look rather high for a dodgy turn! I once scared myself silly when I had an extremely short single axle trailer, delivering cages of groceries to a supermarket in Milton Keynes in the early '80s. I was used to twin axle 40 footers, and I took a 90 degree corner on an A road at a perfectly normal and reasonable speed with this trailer, to glance in the mirror to see the trailer wheel more than two foot in the air. I had enough road space to snap the unit in the right direction and bring it down., and pulled over for a bit of quiet time. The load was a mess when I got there, but no one was duly concerned... another lesson learned.......
That really does look rather high for a dodgy turn! I once scared myself silly when I had an extremely short single axle trailer, delivering cages of groceries to a supermarket in Milton Keynes in the early '80s. I was used to twin axle 40 footers, and I took a 90 degree corner on an A road at a perfectly normal and reasonable speed with this trailer, to glance in the mirror to see the trailer wheel more than two foot in the air. I had enough road space to snap the unit in the right direction and bring it down., and pulled over for a bit of quiet time. The load was a mess when I got there, but no one was duly concerned... another lesson learned.......
Osgood
Western Thunderer
It could work.
Beam compensation allows axle movement in two planes.
Motor / gearbox axle-mounting allows torsional movement of front axle and vertical movement of output shaft.
Tubular bogie trunnion bar and axle mounts provide full support of inter-axle shaft and integrity of bevel drives.
The motor front mount would need some generous freedom to accommodate movement caused by axle twist when at large vertical displacement, so maybe foam mounted to allow few mm up down and sideways? It is a torque reaction drive in any case so this soft mount would cushion jerky speed shifts.
If weight of motor/box is not enough it could be sprung to put greater weight on front axle to assists in unloading rear axle.
Do you have a couple of hours spare after supper?
Beam compensation allows axle movement in two planes.
Motor / gearbox axle-mounting allows torsional movement of front axle and vertical movement of output shaft.
Tubular bogie trunnion bar and axle mounts provide full support of inter-axle shaft and integrity of bevel drives.
The motor front mount would need some generous freedom to accommodate movement caused by axle twist when at large vertical displacement, so maybe foam mounted to allow few mm up down and sideways? It is a torque reaction drive in any case so this soft mount would cushion jerky speed shifts.
If weight of motor/box is not enough it could be sprung to put greater weight on front axle to assists in unloading rear axle.
Do you have a couple of hours spare after supper?
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Giles
Western Thunderer
Absolutely Tony! Though if I were building it I would have the gearmotor some way off and put a Cardan shaft in (I did my first tipper with a Cardan Shaft). The trouble is, If one does a job as good as this, it only does straight lines!
Here's the 4mm Ergonomic finished with a 220mAh battery between the tipper frames
Here's the 4mm Ergonomic finished with a 220mAh battery between the tipper frames
Osgood
Western Thunderer
That would be impressive enough at 1/43 or even 1/50 - I keep having to remember 1/76 is way smaller!
Love the working brake lights - I'd noticed those on one of your cable company videos. Do many onlookers comment on them?
What happens if you ballast the front of the body - does it take away the shudder from the back end when turning?
Love the working brake lights - I'd noticed those on one of your cable company videos. Do many onlookers comment on them?
What happens if you ballast the front of the body - does it take away the shudder from the back end when turning?
Giles
Western Thunderer
Bless you all!
The LEDs are fun. They are 0.6mm x 0.4mm, and thank heaven's, they come pre-wired. With my modelling glasses and magnifiers on top, I can just see which way up they are..... In practise, all I need do is drill a hole, say 0.6mm dia, paint it to provide a little insulation, and wire them up (Using a 4.7K resistor, which is what I have empirically found most suitable).
I've not tried loading up the front end, but with a brass block in there, it does smooth out a bit.
The LEDs are fun. They are 0.6mm x 0.4mm, and thank heaven's, they come pre-wired. With my modelling glasses and magnifiers on top, I can just see which way up they are..... In practise, all I need do is drill a hole, say 0.6mm dia, paint it to provide a little insulation, and wire them up (Using a 4.7K resistor, which is what I have empirically found most suitable).
I've not tried loading up the front end, but with a brass block in there, it does smooth out a bit.
Tim Watson
Western Thunderer
Do you think it would be possible to make a 4mm scale Bullnose Morris four seater work, Giles?
Tim
Tim
Eastsidepilot
Western Thunderer
Giles
Western Thunderer
I'm aware of someone in Germany making ridiculously small vehicles - and a chapnwith the handle 'Otherplanet' has converted a 4mm Scarab to RC, son in theory it's possible. The receiver can't be shrunk, one would do away with the servo, and use an Actuator instead, which is much smaller and less powerful. A very small battery...... finding a small enough motor gearbox combination would be a challenge......