RE: Belt drive vs. Gears?
 

Very imprseeive looking designs! It apperas you could start a nice liitle business here selling belt driven devices for our tanks:D

RE: Belt drive vs. Gears?
 

Here are pics of the new turret drive. A very small surplus gearmotor is mounted in a brass tube (7/16" OD I think). The tube isglued standing upright in the chassis almost directly below the turret gear ring. A brace is also epoxied to the tube. The assembly takes up almost no "floor space". An ovalcollar is made for the motor - with a hole for the motor/tube and room to screw in a desired reduction gear (I used te Tamiya clutch gear) The motor pinion teeth match perfectly to Tamiya gears. The gear obviously has to be screwed in to mesh corectly with the motor pinion. There is a washer under the gear.
Height adjustment is done by sliding the motor up/down in the tube.Mesh adjustment with the main ring is done by rotating the collar so the reduction gear meshes withthe ring.
A hole is drilled near the bottom of the brass tube torun the motor wires out.
I get the motors for $12 at a local surplus place, but they are prabably available online.
The motor/gear assembly is too fast, so i reduce the V to the motor with a 100ohm resistor. Also used the dual rate setting on my Tx to further reduce the turret speed. On the Tamiya KT I get about 25sec for a full rotation.
Very small, quiet and maintennace free.

Note - after the motor and gears are aligned and tested, I used hot glue to secure the motor in position in the tube. The tube itself was seated in a "puddle" of hot glue. The brace was added with black rubberized CA.

Has been working fine for a couple of months in the KT.

The pic is actually in the Tiger 1 now being built. I cut the tube too long it should be shorter with the collar around the motor itself - not the tube, and the motor then free to be adjusted up/down in the tube. I got it right the first time on the KT. Second time on the Tiger 1 I must have had one beer too many...

RE: Belt drive vs. Gears?
 

Pics of gun elevation done with a bungee drive.
Uses Tamiya original turret elev drive, but uses an output pulley to move a bungee up and down vs an output lever arm that had funky and jerky movement.
Elev speed set by choice of pulley diameter and dual rate adjust on TX. Can be run very slow and accurately. Motor/gearbox mounted on a foam pad to reuce noise/vibration.

RE: Belt drive vs. Gears?
 

Now you have my attention.

Can you recommend a pitch, groove and pitch legnth (belt PN#) that could match the Tamiya clutch gear to drive the turret ring gear outside?

I would like to try a belted ring gear for the turret rotation!

RE: Belt drive vs. Gears?
 

How would you get the matching belt teeth on the outer diameter of the turret ring? Also, how would you place the turret and get the belt on around the outside of the ring?
For specific design woud need to know ring diam, locaton of drive, drive rpm, etc etc to get it right. Takes a lot of playing around...
The vertical mini- gear drive actually woks pretty well.</p>

RE: Belt drive vs. Gears?
 

*#%&amp;@!!!*^*** gearbox!
Took the Tiger outside for a test run. Just the hull is finished and all the electronics are in. Made sure tracks were aligned, everything set up right. Had about an hour of indoor run time during build and test.
Some snow still on the ground, but not much - and a warm day - up to 45F!
I must have cursed myself by starting this thread, cuz the Tiger drive gave out after only about 10 minutes!!!!! Tamiya Tiger 1 - big $$$'s. Careful build, etc etc etc. But the right hand drive wheel basically fell off!

Pictures show what happened. This is a desig flaw! Only a 4mm shaft diameterright at a maximum deflection point at the ball bearing. It's amost like it's made to break

I'm not putting a cent into fixing it. Either I get a new shaft free or I really hurry up on the belt drive design and install. I will be using an 8mm dia. shaft the full length of the axle. What a joke (on me I guess)

Good news - the gears didn't strip!

Anybody else see this failure mode?

Enjoy the pics....

Note this is a model of a Tiger 1, late 1944 Warsaw, disabled and taken by Polish Home Army.Just back from repairs, it got ordered to fight ts way through Warsaw and took new damage over just repaired damage.

RE: Belt drive vs. Gears?
 

Thats a new one. Never have seen that failure. Had to have had a stress fracture from the start, that or someone took a hammer too it.

RE: Belt drive vs. Gears?
 

I had a rear idler shear off just like that, but never a drive shaft.

That is truely unique.

RE: Belt drive vs. Gears?
 

Theres a heat vid where dannas sherm always broken suffers that same failure!

RE: Belt drive vs. Gears?
 

Tamiya Cust Service answered in about 10hrs! I'm impressed by the excellent response. They asked for the pics of the failure and my mailing address. They haven't said what they are going to do, but I asked for just the new shaft part. Everything else looked fine when I took the box out. I'm pretty sure they are going to make it right. I did buy it fom one of their authorized dealers.
Dan

Work on the belt drives moving ahead. If it works out, I'll demo it at Danville to get feedback. The more I understand the belts, the better it looks, but I have nothing in hand yet. One very cool thing - box migh be able to be set up with a belt that can bemoved manually to change ratios. Haven't even gotten to thinking about automating that yet....

This hobby is turning out to be very good good vendors, creative people, challenging operational demands on the technology and fun,etc etc. Glad to be here....

RE: Belt drive vs. Gears?
 

We are glad you are here too. Tanking is very addictive. Looks like you were a ship guy, I was heavily into Model Railroading, but the lure of the tank, and the next improvement, keeps my attention focused on these armored beasts.

RE: Belt drive vs. Gears?
 

Tamiya has already shipped a replacement gearbox. Really great product support.

RE: Belt drive vs. Gears?
 

They have a very good reputation for replacement parts that are defective. Gives you a very confident feeling when you buy thier kits.

RE: Belt drive vs. Gears?
 

Belt drive parts have been ordered to build a single drive. Over $80 for the pulleys and belts alone - this better work well. Need to find a cheaper source.
Parts chosen for a 106:1 reduction, similar to my Tamiya gearbox with a Schumo 3:1 reducer.
Will post pics when built.
Pulleys are acetal (delrin).Belts are fiberglass reinforced urethane. Belt width 6mm. These parts are rated for pretty high loads. My KT weighs almost 14 lbs.May test by using the drive to hoist weights vertically and see how much it can lift before slipping. I'm pretty sure the motor will stall long before the drive capacity is exceeded. We will see....

RE: Belt drive vs. Gears?
 

Ah Ha!!!!! The pulleys and belts are here. Looking great.... No time to bild the drives up now, but real quick took some pics. The belt drive can be set up in a very similar size geometry to a Tamiya drive, but the ratio is about 105:1 vs only about 60:1 on the Tamiya stock box. Determined ratios by output RPM with a tachometer. Also calculated the pulley ratios on the belt system. The Tam box has so many gears, etc, I don't have the time to actually count and calc the ratio on that box.

Anyway, real quick put the pulleys on two brass tubes mounted in a vice, strung the belts and drove the box with a Tamiya stock motor. Even though the shafts were sloppy, beltswere looseand alignments were off, the drive ran great and the Tam motor was by far the loudest part of the system. Belts will be VERY quiet. I then put on a very quiet Faulhaber motor and the drive purred.

I tried to stop the final pulley by hand. Could not stop it, but slowed it way down and was able to slow the motor down. NO belt slip and I didn't even have the beltstight in the vice set up. And the brass tube axles were only supported on one end. I realy think motor will stall before belts slip (depending on tension set up - in R/C tugboats, I leave the belt just slack enough to slip when the prop gets fouled - then you hear a loud rattle sound as the teeth slip - perfect warning system)

This is going to work! All the belts I ordered are too long - must get that figured out. Also, the ratio may be too high. So even smaller pulleys can be used. Note that the motor can be mounted in many ways because you can choose a belt length that allows placing the motor away from the drive if necessary. Also, the front end dimensions would allow the final drive pulley - mounted on the axle - to be moved forward into the tightest of spaces.

I'll get video with sound of a Tamiya box, belt drive box, etc in a couple weeks. Hope to have a prototype box to show at Danville.

Pics attached - amazing that so few pulleys are needed and that there are SO many parts in a regular gearbox. And no lube is needed!

RE: Belt drive vs. Gears?
 

This is exciting!  The possibilities this opens up are endless...perhaps I can now make that M5 Stuart in 1/16 that I've been wanting...Sweet!  Keep up the good work and put me down for a pre-pre-pre-order set :P 

RE: Belt drive vs. Gears?
 

I hope you have a worknig set of these at Danville.!!!!!

RE: Belt drive vs. Gears?
 

YHR - whew I feel like I'm not retired anymore....
I can't get the parts I need in time and don't have the time to get a working set put together anyway. But I will have a demo drive at about the right ratio that will be real representative of an actual tank unit.

Some questions for anyone interestedplease -

1. For battling/competition, what balance of speed vs power do you want most? Pick a number from this example:

Tamiya KT: Stock drive (60:1)Withreducer to 112:1 total drive ratioWithreducer to 180:1 total drive ratio
25+ smphabout 13 smphabout 8 smph
<span style="font-size: larger"> 1 2 3 4 5


2. Is a two-speed gearbox needed?Must have Nice to have Maybe No


3. What is your favorite motor? Do you know its' RPM at 7.2V?


4. Would a "low amp-draw" motor/gearbox be veryimportant or not such a big deal?


Thanks! Dan</span>

RE: Belt drive vs. Gears?
 

For me it is all about torque. I want something that pulls hard and slow. I don't like jack rabbit starts, and a tank that just zooms around. So a good top speed is fine if it starts slow and pulls hard until it gets there. So a 2, nice to have, 11000 rpm and a low amp draw

RE: Belt drive vs. Gears?
 

A speed between 25 and 13 mph would be an ideal setting for most WWII tanks, for both realism and drivability.

Notice that picking a motors maximum voltage efficiency curve at say 4-5 volts (rated) will help with the torque issue.

Motor draw is not much of a concern for these small motors, although the 540's in the leopard could benefit from lower draw motors, without sacrificing speed, to extend battery life.

RE: Belt drive vs. Gears?
 

Great info. Thanks for participating in "product development" Could use more input.

What are the top 5-6 tanks (by how many are out there) besides KT and T1?

What are the driver diameters at the outside of their tracks?

Waht is the desired top speed in competition while still keeping desired torque "pulling power".

What is "too much" for average drive amp-draw for competition? Or better - how much run time do you get from a specific battery in a specific tank?Need any info
on the battery rated capacity (mAh), type of tank/gearbox (gearbox ratio), and how long it runs

Thanks!
Dan

RE: Belt drive vs. Gears?
 

I saw an interesting review of a Schumacher Mi 1 4wd 1/10 scale sedan in the June issue of RC Driver magazine. The writer states that the "two belt drive system is a tried and true setup". This is a toothed belt with a"belt tention puley". They do have a picture that shows thebelt and the pulley. I visited theSchumacher site (a British company) and they use belts in several cars.They do have parts for sale. I am sure that someoneon this sitemust have some hands on experience withbelt driven cars. I look forward to someone producing a reliable systen. The still frozen tundra.