Author Topic: M5 Stuart Light Tank  (Read 8785 times)

Offline crueby

  • Full Member
  • *****
  • Posts: 18555
  • Rochester NY
Re: M5 Stuart Light Tank
« Reply #15 on: January 17, 2021, 08:04:33 PM »
That steering box is very clever! Are there plans or a design document available for that?

Fascinating stuff!    :popcorn: :popcorn: :popcorn:

Online tghs

  • Full Member
  • ****
  • Posts: 1034
Re: M5 Stuart Light Tank
« Reply #16 on: January 17, 2021, 08:42:59 PM »
I stared at the photos a good while untill I noticed the idler gears on the back wall.. :facepalm:
« Last Edit: January 17, 2021, 10:46:14 PM by tghs »
what the @#&% over

Online Vixen

  • Full Member
  • *****
  • Posts: 3075
  • Hampshire UK
Re: M5 Stuart Light Tank
« Reply #17 on: January 17, 2021, 08:48:25 PM »
Hello Chris

Iliya Cerjak had a website dedicated to tank transmission design. He produced a number of different designs, some good and some even better. The various designs were free to download, other than a voluntary contribution to any charity of your choice. Unfortunately, the website has been taken down and no longer exists. Websites cost money and Iliya's website was non money maker.

The CT1 design I used for the Stuart is only suitable for model tanks and tracked vehicles up to a weight of about 15Kg. Together, we developed other transmission designs for heavier and more powerful model tanks. An all metal 1/6 scale Tiger tank can weigh in at over 60 Kg.

Wait for a while, until I have discussed the CG2 DD transmission system used in my all metal StuG 111, which weighed in at around 45Kg.  If you are still interested, I will see what can be done to help you.

Stay safe

Mike
« Last Edit: January 27, 2021, 01:27:28 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Online Vixen

  • Full Member
  • *****
  • Posts: 3075
  • Hampshire UK
Re: M5 Stuart Light Tank
« Reply #18 on: January 17, 2021, 08:51:37 PM »
I stared at the photos a good while untill I noticed the idleler gears on the back wall.. :facepalm:

Well spotted.  :ThumbsUp: :ThumbsUp: Yes,  that little idler on the back wall is there to reverse the direction of rotation of the intermediate shaft when the reverse clutch is engaged.

I have just looked through my photo album to see if there is a better photo showing the reverse idler. The idler is always lost in the shadows, so the first photo is the best I can offer

Mike
« Last Edit: January 17, 2021, 08:59:06 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 6133
  • Switzerland
Re: M5 Stuart Light Tank
« Reply #19 on: January 18, 2021, 12:37:53 PM »
Lots of fascinating details :)  :)  :)  :wine1:

Thank you for deciding to post these model builds  :ThumbsUp:  :ThumbsUp: You had made a few tempting comments in the past and let a few secrets out like the epycyclic gearbox  :paranoia:
Best regards

Roger

Online Vixen

  • Full Member
  • *****
  • Posts: 3075
  • Hampshire UK
Re: M5 Stuart Light Tank
« Reply #20 on: January 18, 2021, 05:03:48 PM »
Thank you Roger,   :ThumbsUp:

You know as well as anybody, just how much time and effort is involved in posting a log.   I am pleased to hear you are finding some interesting content.    Hopefully, there may be more to follow.

Mike   :atcomputer:
« Last Edit: January 18, 2021, 05:16:19 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline nj111

  • Full Member
  • ****
  • Posts: 144
Re: M5 Stuart Light Tank
« Reply #21 on: January 18, 2021, 05:10:44 PM »
This is fascinating Mike.   I'm sure I saw this at the Bristol show maybe 15 or more years ago?   I also have the same Seidel 5 cyl Engine , of similar age and still with it's original maker's chipboard box. Not actually run it yet!
Nick

Online Vixen

  • Full Member
  • *****
  • Posts: 3075
  • Hampshire UK
Re: M5 Stuart Light Tank
« Reply #22 on: January 18, 2021, 06:20:33 PM »
Hello Nick,

The tanks were displayed at a number of shows about that time.

Best advice is to keep your Seidel in it's box. Once you run it, the caster oil gets everywhere and it's almost impossible the get it off.   :noidea:

Mike
« Last Edit: January 18, 2021, 10:33:55 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline Laurentic

  • Full Member
  • ****
  • Posts: 309
  • Nr Yeovil, Somerset, England
Re: M5 Stuart Light Tank
« Reply #23 on: January 19, 2021, 12:31:22 PM »
Very interesting and intriguing - but I'm still trying to work out that gearbox/clutch arrangement in my head!

Chris


Online Vixen

  • Full Member
  • *****
  • Posts: 3075
  • Hampshire UK
Re: M5 Stuart Light Tank
« Reply #24 on: January 19, 2021, 03:12:53 PM »
Part 3    Running and Testing

My Stuart tank was always intended to be a working tank, an engineers tank, to be driven hard, to be broken, fixed, modified and improved.  Not for me, a pristine show piece with authentically weathered paintwork and a crew of 1/6 scale dollies all in matching uniforms.

Engine. The Seidel ST540 is a 40cc five cylinder radial engine. It runs on a synthetic oil in methanol fuel mixture with glow plug ignition. The engine/ gearbox arrangement means the maximum engine speed was around 4000 rpm. The engine was supplied, from new, with a glow plug driver module, which could be switched between full voltage for starting, reduced voltage for running or switched off entirely (for flying?) At tick over and below 4000 rpm, the engine would not run cleanly without additional battery power to keep the glow plugs hot. This meant the tank had to carry the glow plug battery around all the time. Approximately 10 Amps were required during start-up, which could be reduced to about half that amount, when the engine had warmed up.

The fuel was 10% synthetic oil in straight methanol with no additional nitro methane.  The fuel mixture was drawn into the crankcase before being distributed to the five cylinders. The fuel oil mixture lubricated the crankshaft and con rod bearings and also the cam ring gears. !0% oil is a much lower percentage to that used by most single cylinder RC engines. It's what Seidel recommended and gave no trouble. I also meant that there were no visible smoke emissions, allowing me to operate the tank in indoor arenas without complaint.

The carburetor was a small 6 mm choke OS Max air bleed carb, typical of those fitted to RC engines of about 8 cc. The air bleed adjustment is used to set the air/ fuel mixture at tick over, the single needle valve is adjusted to set the air/ fuel mixture when the throttle is open. I found the engine would start easily and tick over smoothly with the throttle closed, The main needle jet could be adjusted to get the engine to run smoothly with the throttle 100% open and down to about 70% open. Below that, the mixture needle needed to be manually readjusted to match the reduced air flow. Adjusting the needle valve and air/fuel mixture was not possible via the radio control. I found the usable throttle range could be extended a little, by running the engine slightly on the rich side. This was possible because methanol has a wider burn range than gasoline. The richer mixture also provide extra engine cooling (through evaporation) and ensured adequate lubrication. This somewhat limited throttle range at the top end is of no real consequence when an air screw is fitted but is a limitation to the drive-ability of a wheeled or tracked vehicle.

A variable jet carburetor or a constant velocity (SU style) carburetor, similar to the ones Roger B is developing, could potentially prove useful to open up the throttle range over the simple OS Max style air bleed carbs. I do not have such a carburetor. Instead, I decided to operate the engine at a more or less constant speed, in the middle of the available throttle response range, and to design and fit an additional two speed gearbox to control the tanks actual speed. See below.

Transmission.  The nylon worm gears were damaged early on so they and some of the other spur gears were replace with steel gears and gave no more problem. Gear lubrication was by grease applied by brush to ensure an even distribution. The grease lubrication proved to be quite adequate, as shaft rotation speeds were low

The four multi plate clutches needed to be pressed hard to be fully engaged, all the time. This caused undue loading of the servos and the thrust bearings. The servo's force limits the amount of pressure that could be applied to the clutches, which would slip if overloaded. Any clutch slip tended to polish the friction plates and the clutch performance would suffer. The clutches would need to be removed and roughed up with sand paper to restore the friction. I considered replacing the fibre glass laminate clutch plate with plywood plates or some other material, but never actually got round to it. The risk of clutch slip meant I had to limit the tank driving to hard paved surfaced or very short grass. Long rough grass was always a problem.

Tracks and Running Gear The plastic tracks, wheels and suspension proved to be quite tough and able to withstand the abuse. The short outer connecting pieces between the track plates sometimes broke (just like the full size tank) I made a batch of replacement parts out of polycarbonate which worked well. The hull was made from a different type of plastic to the tracks. It was not as tough and cracked easily, cracks would grow from all the bolts holding the hull together, which had to be patched.

Two speed gearbox An additional two speed gearbox was added to provide better overall speed range to the tank. It was found that a top speed of little more than fast walking pace was adequate, otherwise you ended up running to keep up. The low gear ratio allowed a lower vehicle speed for maneuvering in tight places and for climbing hills. The engine was run at more or less constant speed, the gearbox changed the vehicles speed across the ground.

The two speed gearbox was a cut down version of the steering gearbox. The idler gear, necessary for the reverse operation, was not fitted. The gear ratios between the upper input shaft and the lower output shaft could be changed by altering the tooth count of the spur gears.








I hope you find this feedback both interesting and informative. The notes on the engine performance can be applied to other miniature four stroke engines, both single cylinder or multi cylinder. Some parts may also apply to two stroke engines.

Stay tuned, there is more to follow

Stay safe

Mike   :atcomputer:

« Last Edit: January 19, 2021, 05:45:53 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline crueby

  • Full Member
  • *****
  • Posts: 18555
  • Rochester NY
Re: M5 Stuart Light Tank
« Reply #25 on: January 19, 2021, 06:19:05 PM »
Wonderful!  I find those gearboxes fascinating.

Online tghs

  • Full Member
  • ****
  • Posts: 1034
Re: M5 Stuart Light Tank
« Reply #26 on: January 19, 2021, 07:21:49 PM »
so are there 2 small bearings in the clutch yoke arms? I guess in this case they would be referred to as throw in bearings..
what the @#&% over

Online Vixen

  • Full Member
  • *****
  • Posts: 3075
  • Hampshire UK
Re: M5 Stuart Light Tank
« Reply #27 on: January 19, 2021, 07:55:00 PM »
You all seem to be fascinated by the CT1 steering gearbox. There are some drawings for you to see how it all goes together. The two speed gearbox was also based on part of this design but without the reverse idler gear.



Hope this helps. You should be able to work out how it happens from these.

Mike :atcomputer:
« Last Edit: January 19, 2021, 08:04:22 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline petertha

  • Full Member
  • ****
  • Posts: 782
Re: M5 Stuart Light Tank
« Reply #28 on: January 19, 2021, 08:05:08 PM »
Now that I see the layout, I'm even more impressed the servo can actuate engagement with normal arm rotation. I know nothing about clutch design. For example does adding more plates change the input force to engagement or just modify how the slip transitions? Do you recall nominal torque rating of the servo?

Online Vixen

  • Full Member
  • *****
  • Posts: 3075
  • Hampshire UK
Re: M5 Stuart Light Tank
« Reply #29 on: January 19, 2021, 08:17:24 PM »
Peter,

Any clutch is all about coefficient of friction, surface area and contact pressure. the more you have of these, the greater the torque that can be transferred. Multi plate clutches get more surface area into a given space.

RC servos come in different sizes, chose one with an adequate thrust (force) rating to press the clutch plates together. I used a 'standard' servo, Typically 5 to 10 Kg thrust.

Mike  :atcomputer:
« Last Edit: January 19, 2021, 08:29:39 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal