Supporting > Vehicles & Models
M5 Stuart Light Tank
AVTUR:
--- Quote from: Vixen on January 16, 2021, 03:16:37 PM ---
--- Quote from: tghs on January 16, 2021, 03:06:47 PM --- the main drawback was the high profile of the vehicle making it an larger target, Gasoline was also a risk compared to diesel, but one good hit didn't really matter what kind of fuel was used..
--- End quote ---
Gasoline was always the fuel of choice, everything, including the cookhouse stoves ran on it. It was a question of logistics, one fuel ran all. Supplying more than one type of fuel to the forward troops was out of the question.
As to the vulnerability of gasoline v Diesel. It did not matter much. One good hit would usually set off a ton of high explosive ammunition first.
Mike
--- End quote ---
The German army ran on hay all the way through the War. They had to. The only thing I do not understand is why they, the military, did not just give up.
There was a piece of amateur movie film shot by a Frenchman in the summer of 1944 near Falaise. The morning filming, done secretly, shows Germans retreating with big artillery pieces being drawn by horses. The afternoon filiming is of the arriving allies, completely mechanised.
On second thoughts, there is a lot I do not understand about WW2.
petertha:
Sorry for some more tangent questions Mike. Pertains to a similar radial I'm building.
- I'm assuming the ignition module shown a Seidel original part? I cant seem to find much info on it, but maybe you know. After startup, does it continue to drive the glow plugs on high, or switch off, or revert to reduced current?
- was the ring exhaust assembly stock & modified or you made yourself?
If I have the story straight, Seidel's were actually pretty good RC engines. Eventually went out of production. Then my scent gets cold - picked up by a Swiss company & no more? I've also found links to HobbyKing (Chinese copy or maybe just distribution).
Interesting link of Seidel mods FWIW. I wish the web pics could expand, there are some good internal details throughout.
https://www.heilemann-sternmotoren.de/en/modification-seidel
https://www.heilemann-sternmotoren.de/en/ring-of-muffler
Vixen:
Hello Peter,
You are as impatient as ATUR, getting ahead and asking questions about things I have not yet come to.
But to answer your questions. The glow plug driver module provides full voltage during start up, it can be reduced or switched off, when the engine has warmed up. In the Stuart tank installation, the engine never reaches high revs (unlike in an aircraft) so I always ran at the reduced voltage setting. Five glow plugs consume something like 10 amps from the battery at the full setting, deducing to about half that at the reduced setting. It all meant the glow plug battery needed to be big and heavy and carried on-board the model tank.
The exhaust ring was home made from domestic 15mm copper tube bent into two half circles and joined. The five compression fittings, with fat rubber glands, were soldered to the exhaust ring. I used soft lead free solder, not silver solder. Methanol fuel burns at a much lower temperature than gasoline. The soft soldered joints lasted well, provided I ran a rich mixture; until one day when I had a very 'lean burn'. Silver solder or TIG would be much better....... If only.
The five compression glands were made from recycled BNC co-axial video signal connectors. I soft soldered a standard 15 mm copper compression gland (olive) to join the two halves of the collector ring
Not realy sure what went wrong for Siedel, Last I heard, they were now being manufactured in India.
Thanks for the two links. I am going to enjoy studying them.
Go safe
Mike
To quote from one of your links "Why some parts have obvious hammer marks – probably only the Indian precision mechanic knows." :hammerbash:
petertha:
Thanks for the details. I'll throttle my enthusiasm & lay low now so you post without (too many :D) distractions. You obviously did some detailed work on the powerplant side which I'm really looking forward to see as the story unfolds. Very interesting project!
Vixen:
Part 2 Steering systems
As we all know, a tracked vehicle is steered by reducing the speed of one track. When this happens, both tracks are forced to skid sideways over the ground. This action produces massive (sometimes destructive) forces on the track links, wheels and running gear and especially the transmission system. The steering loads require maximum power from the engine. The magnitude of the steering forces are very dependent on ground conditions. Smooth hard paved surfaces are much kinder than soft or rocky ground. For a model tank, even long grass can can provide difficult conditions.
Most model tanks have two powerful electric motors, their speed being varied independently by radio control. I did not want to follow this route. I wished my model Stuart tank is to be mechanically powered so I needed to devise a mechanical steering system. In full size tanks and tracked vehicles, there are a number of ways to do this, some are quite basic and some more sophisticated. Among the possibilities are:
1 Clutch/ Brake steering. Here the drive is removed from one track and a powerful brake is applied. The disadvantage is a jerky uneven ride as the vehicles forward speed is suddenly reduced by half during the turn.
2 Braked Differential steering A powerful brake is applied to one side of a differential to slow that track, the track on the opposite side increases speed and the vehicle turns very quickly. Such a high rate of turn is uncomfortable and undesirable, so this system is usually only used on very light tracked vehicles such as the Bren Carrier.
3 Controlled Differential steering A more sophisticated system which produces fixed radius turns. It was widely used on the early US tanks.
4 Double Differential steering A more complex system where an external, variable speed, steering shaft is applied to two differentials. One track speeds up and the other slows. This system can provide infinitely variable turn rates and steering not unlike a wheeled motor vehicle.
For my model Stuart tank I decided to build a CT1 steering gearbox based on a design by Iliya Cerjak, a brilliant young Dutch engineer who works in Amsterdam's University. The central drive shaft from the engine supplies power to two sets of multi-plate clutches, one for each set of tracks. The multi-plate clutches are operated by servos via a wishbone arm, fitted with roller bearings. The clutches engage the engine power and turn the intermediate shaft in either direction. The intermediate shaft turns the worm wheel in the final reduction dive in either direction. The worm and pinon arrangement was chosen for the final drive reduction (30:1) because a worm and pinion can effectively lock (brake) the tracks when neither clutch is engaged (centre position).
The CT1 gearbox allows each track to move forward , backwards or lock.
Here you can see the components of one set of multi-plate clutches. The friction plates were made from laminated printed circuit board (with the copper foil removed). Their serrated outer edge are a sliding fit in the aluminium clutch spider. The driven plates are made from steel sheet
The centre of the clutch spider was broached with a hexagonal hole and is a sliding fit over a short length of hex bar attached to the input shaft. It's a poor mans splined shaft. The steel drive plates also have the broached hexagon hole and they fit over the hex extending from the output gears. The multi-plate clutches operate at engine speed and therfore see lower torque than if they were at the output shaft end, so can be comparatively small in diameter
The servo controlled wishbone arm fits between the two multi-plate clutch sections. The use of nylon for the gears was not a good choice and they were soon replaced with stronger steel gears.
Here you can see the CT1 steering gearbox installed in the front of the model Stuart tank. The linkage between the servos and the clutch control arms have not yet been fitted. The clear poly-carbonate top cover for the gearbox was useful for seeing what was happening inside. Gear lubrication was by grease (applied with a stiff paintbrush). Only a small amount of grease was applied, for fear of lubricating the friction plates of the clutches.
The movement of the two servos had to be carefully adjusted to ensure the clutches were fully engaged at the end of the servo's travel. There was always a risk of the servos stalling (and burning out) if they could not reach the end of their travel, so I fitted two adjustable coil springs in each control rod to prevent this overload situation from happening.
My Futaba radio control set allows electronic mixing of the control channels. I set the right hand joystick to control the steering gearbox. Stick forward; engaged both forward motion clutches, rearward stick motion would put the tank into reverse. Side motion of the joystick would disengage the appropriate clutch and the model tank would turn. I used the left hand joystick for the engine throttle servo
I was now in a position to fill the fuel tank, switch on and start the engine for the first time. Then began the fun time of seeing what worked, what didn't, what needed modification. I always enjoy the development phase.
Did I ever tell you that I like engines and mechanisms? :noidea:
Mike
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