4.1 Gearbox Question
 

The 4.1 gearboxes have more torque from what I understand, so what does that actually mean? Runs slower vs a 3.1? Better ability to traverse obstacles? Both of my current tanks have 3.1 gear boxes.....I think. My Tiger 1 seems to run a little smoother at lower speeds than my Panzer III does so far. Maybe some more running will improve on the Panzer III.

The extra gear results in a lower top end, but more grunt. For most tanks this will improve the running performance, and give you better smooth slow speed control.

What Dan said. You get much better and more realistic low speed operation with four shaft boxes, but less top speed than the three shaft boxes. So, depending on what tank you have you may want the three shaft for higher speed, but I think that would only be modern tanks. I plan to get an Abrams and it will get the three shaft boxes with the 360 motors for more realistic scale top speed.

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That's why I always refer to them as three SHAFT and four SHAFT boxes. In between the pinion at the motor and the gear on the axle you have either three or four gearshafts with reduction gears. To me using three shaft and four shaft as opposed to 3:1 and 4:1 is much more accurate and much less confusing. The number of shafts doesn't have anything to do with final drive ratios, it's just a quick way to identify the different boxes, and to me it only applies to the stamped steel sided boxes like the standard in HL tanks. You'll never see me refer to a gearbox as 4:1 or 3:1, I always identify them by the number of shafts.

The number of teeth in the gear has nothing to do with it, it's all about revolutions. If your pinion has to make two complete revolutions to make the connecting gear turn one revolution, that's a 2:1 ratio (or possibly 1:2, I always get that part mixed up). Like automotive rear ends that are referred to as 4:11 gears. That means that for every time your driveshaft turns 11 times your tires turn four times.

Max, right you are. See these posts for gearbox calculation. Hope it makes it more clear...maybe more confusing...

http://www.rcuniverse.com/forum/rc-t...l#post12002365

Making things more confusing is what a good hobby does. :)

Good info though. Will be a little while before I do any big mods to anything. I can see steel 4.1 gear boxes in the future though. I prefer prototypical low speeds.

wait a bit longer. Erik has steel all bearing gearboxes coming out in the next couple of weeks. Wait until those babies are out then get some

wait a bit longer. Erik has steel all bearing gearboxes coming out in the next couple of weeks. Wait until those babies are out then get some

I have 3 shaft gearboxes with bearings on all the drives and they are sweet. If someone starts making these with four shafts then they would be great in WWII armor. Like Gary says though, on the stamped boxes count the shafts, as when someone started calling HL standard gears as 3:1 a whole bunch of confusion was born. Gary came up with the shaft count as a better identifier, and it is what I use now as well.

WSN

It is just easier to count the shafts then to have to tell the story of why 3:1 and 4:1 are exactly the same gearbox to us old timers who referred to the 3 shaft boxes as standard gears, and the 3:1 as lower geared 4 shaft version. The reason we called them 3:1 was because the out put shaft turned 3 times slower then the standard boxes. Someone then came on here and started calling the standard gears 3:1 and the lower ration gearboxes 4:1. You could tell when someone entered the hobby just by how they identified these gears:D It was mass confusion until Gary identified it would be easier to identify the two gearboxes by the shafts. I am sure more then one guy has bought 3:1 gears thinking he was getting a lower ratio only find they were exactly the same as what he already had.

Ive said only that so called "3:1" and "4:1" HL gearboxes have the same gear ratio and Im not described them as the "standard" HL gearboxes /with one gear less/ . But to avoid any confusion Ive deleted my previous post. The descriptions "3:1" or "4:1" HL gearboxes was introduced by suppliers not by me. I dont see difference between them because both have the same amount of gears and shafts - four .The standard HL gearboxes with three shafts was sometimes called by some suppliers "2:1" - I dont know why too.

for example
3:1
http://www.rctank.de/31-PRO-steel-ge...m-/-long-axles
http://www.rctank.de/31-PRO-steel-ge...-/-short-axles

4:1
http://www.rctank.de/41-PRO-steel-ge...-motors/18000t
http://www.rctank.de/NEW-STEEL-LOW-R...RBOXES-TIGER-I

No need to delete anything, as you and I know these boxes by a different name. It is just between all the new guys and then suppliers throwing their own terminology around it gets to be very confusing for the new guys starting out what they are actually buying!!!!

I wasn't taking you to task, just merely taking the time to point out the confusion that exists surrounding gears.

If you look closely at the gearboxes you use for examples, the ones you have listed as 3:1 have three small bearings on the side of the box. Now go to the ones you list as 4:1 and you'll see it has 4 bearings visible. There's an extra, small reduction gear right at the pinion, giving these an extra reduction gearshaft, for a total of four shafts in between the pinion and the gear on the axle. The first sets you show (3:1) don't have that extra shaft and there's only three shafts in between the pinion and the gear on the axle shaft. That's why the 4 shaft boxes are only available in high/low configuration, because on a mid or low you can't get that fourth shaft in there. This is why I refer to them as 3 shaft and four shaft gearboxes. The main problem was that the old hippie brain got too confused and needed a quick way to identify the difference, so I thought, "why not just count the gearshafts that have reduction gears on them". The 4 shaft have an extra reduction gear.

The suppliers starting this 3:1 and 4:1 stuff just made it confusing for us all. The true final drive ratio is easy to explain, how many times does your pinion gear have to turn to turn the axle one rev? If your pinion turns 100 revolutions to make the axle turn one revolution you have a 100:1 final drive gear ratio (or vice versa, I already said I always get that mixed up so it might be 1:100). Easy to explain, much more difficult to calculate. I'm not going to turn that tiny little pinion by hand to find out how many times I have to turn it to make my sprocket go around one time. I bet it's a lot! I guess one way would be by RPM, if you had something that can detect pinion RPM and axle shaft RPM, like they use for airplane props, but I don't know of any such device.

I agree with Dan that you should not have deleted your post. The tooth count info is very helpful when changing the pinion gears. Now I wish I had made a copy of that. There's no such thing as too much information. :)

Gary and dan both have good points on your post. I kinda wish it was still there if nothing else for reference. i hope that you think about reposting it. i remember when I used to race offRoad RC. i would drive myself crazy with diffent pinion and spur combinations trying to get the "perfect balance" of battery life to speed to torque. aside from the names of 3:1 and 4:1 i think that most of the people that visit the forums would agree however you decide to classify or define what type of gearbox you have that info like gearing and tooth count would still be welcome.

All a long I thought gear-ratio i.e, 3:1, 4:1 were about speed ratio just like in real actual gearboxes - input gear to output gear.

I though that 3:1 was faster and 4:1 was slower.

By looking at the Taigen gearbox I have with me right now (TAG120264 58mm), I counted 4 SHAFTS. Is this correct, Gary?

Thanks for clarifying all this confusion about gear ratio.

I know there are many different motors and gearboxes out there, but here's some hard data on Tamiya gearboxes and motors:
Actual RPM's were measured with a tachometer and the gearbox ratio was determined by actual manual rotation count.

Four stock Tamiya motors were measured. All were almost exactly the same RPM. Average [email protected] no-load: 16,600 RPM
An ETO "Long-black" upgrade motor was also measured. [email protected] no-load: 17,300 RPM

A standard Tamiya gearbox (measured from my KT and T1) with a standard 10-tooth motor pinion has a ratio of 60:1 (60 motor revs = 1 wheel rev)
That calculates to 266 wheel RPM at full no-load motor speed of 16,600 RPM.
266 wheel RPM calculates to a scale speed of 26 MPH (for a Tam KT and T1, each with 2" diameter drive wheels).
My actual KT top-speed measurement comes out at 22 scale MPH, slightly slower than the calculated 26 MPH.
The slower speed is due to the slower maximum motor speed under load vs the higher no-load RPM.

Note: the Tam gearbox ratio, not including the motor pinion (10 tooth) is 600:1.

So all this 4:1 and 3:1 nomenclature really lends confusion, since the gearbox ratios are actually up in the 600:1 range.
The 3 and 4 shaft count description is one way to generally describe gearboxes, but it's the number of gears on each shaft and their tooth-count that determines gear ratio, not just the shaft count.
So neither method, shaft count metod or 3:1/4:1 method, are accurate ways to describe the actual gearbox ratios.
I can provide example calculations if wanted.

Wow thats great. danirc so can you tell me how to actually get the reading of the RPMs from my motors do is it bet to just scour the interwebs unitl i find something. what is the best way that you have found to calculate scale speed. As far as the 600:1 ratio I can see that being a bit more accurate than 4:1. They really just need to change how they label the gearboxes. Even just a basic description like (3;!= higher to speed less torque, 4:1= lower top speed higher torque) or something.

As for the three and four shaft names, I just thought it was a quick and much more accurate way to identify gearboxes at a glance. Perhaps this video will clear things up. All I'm really after is for us all to be on the same page. What term we finally decide on doesn't matter. The three and four shaft names aren't supposed to have anything to do with gear ratios, it's just a quick way to identify which box it is.

https://www.youtube.com/watch?v=rKz1rTDO2qY

Excellent explanation.

Thanks for clarifying this, Gary.

Excellent description and explanation.

Thanks for clarifying this, Gary.

Excellent description and explanation.

Max, I agree with you 100% that 3-shaft/4-shaft is a good quick way to identify different gearboxes. But to figure out the exact top speed you will get, requires knowing the motor RPM, the actual gearbox ratio and the diameter of the drive wheel.

The simplified calculation, including the 1/16 scale speed factor, etc etc is:

Scale speed, in scale MPH = ( Motor RPM / gearbox ratio) x drive wheel diameter in inches x 0.05

Example for a Tamiya KT:
Scale speed, MPH = (16,600 motor RPM / 60 gear ratio) x 2-inch wheel diameter x 0.05 = 27 scale MPH

The actual top speed will be a bit slower - maybe 4 to 6 mph slower - because the motor under load will be slower than the measured no-load speed of 16,600RPM. Also, fully charged batts (about 8 to 8.4V) will kick up the speed over the 7.2V nominal voltage.

To get motor RPM, I glue (with CA) a small 2-blade RC plane prop on the shaft end and measure the RPM with this tachometer:
http://www3.towerhobbies.com/cgi-bin...P?I=LXYXK9&P=8
When I measure, I also hook up a voltmeter to get the actual voltage to the motor when the RPM is measured.

The tach does not work under indoor lights (because of the AC 60 cycle flicker in the lights). Need to make the measurement outdoors or in a bright room indoors with no lights on.
Measurements are very repeatable.