Rumors of Future Releases

[Milspec1]

Lucky!

[tank_me]

Just a heads up on the Stuart tanks. It shows that it was flown over and is getting closer. Shows arrived shipping partner facility USPS awaiting item Canal Winchester, which is about 30 miles away.

My twin Stuarts arrived today... :)

[Milspec1]

Just a heads up on the Stuart tanks. It shows that it was flown over and is getting closer. Shows arrived shipping partner facility USPS awaiting item Canal Winchester, which is about 30 miles away.

[keilau]

Hi, I know this is a few replies ago, but I couldn't just read this and not correct it. You're completely missing a step in your equations. Namely, motor rpm x gearbox ratio DOES NOT EQUAL track rpm. Motor rpm x gearbox ratio gives you the drive sprocket rpm, which is NOT the same as track rpm.

Drive sprocket rpm converts to track rpm by the ratio of drive sprocket circumference to track length.
For example, a 1 inch diameter drive sprocket (3.14in circumference) will turn roughly 10 times for one full revolution of a 30inch long track. In this way, like SoCalBobS mentioned, the drive sprocket can be seen as the final gear in the drive train.

This means that a drive sprocket twice as large in diameter will make the tank drive twice as fast.

This fact illuminates the other incorrect claim you made, "When you use a larger diameter sprocket, you need to increase the track length to go around it. A longer track means faster tank speed."
For the same tank chassis, say 15 inches long, going from a 0.5inch sprocket to a 1inch sprocket won't increase the total track length by more than 2 inches, so by your reasoning you'd only see a speed increase of 2/15 or ~13%, when in fact this change will make the tank twice as fast. The tradeoff is that the tank will have half the amount of torque (and thus acceleration) at the ground, and will take longer to reach that top speed.

All of this is taking an unnecessary detour though, the track length itself is actually irrelevant. The drive sprocket in a tank functions no differently than the wheel on an rc car, and we know that at equal drive shaft rpms, a wheel twice the size will make the car go twice as fast. To convince yourself of this fact, imagine if you lowered or compressed the tank until the drive sprocket was in contact with the ground. Now the track is effectively just another layer of pavement, and the drive sprocket rolls without slipping along the ground, the same that a driven wheel on a car would.

Equations:
Motor rpm * gearbox ratio = drive sprocket rpm
(drive sprocket circumference / track length) * drive sprocket rpm = track rpm
track rpm x track length = rc speed.

Putting it together:
Motor rpm * gearbox ratio * (drive sprocket circumference / track length) * track length = rc speed.

notice how track length cancels out since it is in the numerator and denominator of the combined formula.

LegoDEI , thank you for correcting my huge mistake. That's what a 7 years retirement can do to a used to be sharp mathematics mind. I never used those equations to calculate the track rpm and should not have list them. Much less arguing that others were wrong. A big red face.

After I complete my RC tank, I tested different 380/390 motors. The tank was put on a 2x4 dynamo. I use a hand held tachometer to measure the track rpm and calculate the scale speed. Below is a table of the 1/16 scale Heng Long Pershing with a Torro series 2 gearbox. Just an example.

[SoCalBobS]

Lego, you're right. Thanks.

[LegoDEI]

I'm still hanging at JPL haha, trying to avoid getting laid off 😅

[Rubicon99]

Hi, I know this is a few replies ago, but I couldn't just read this and not correct it. You're completely missing a step in your equations. Namely, motor rpm x gearbox ratio DOES NOT EQUAL track rpm. Motor rpm x gearbox ratio gives you the drive sprocket rpm, which is NOT the same as track rpm.

Drive sprocket rpm converts to track rpm by the ratio of drive sprocket circumference to track length.
For example, a 1 inch diameter drive sprocket (3.14in circumference) will turn roughly 10 times for one full revolution of a 30inch long track. In this way, like SoCalBobS mentioned, the drive sprocket can be seen as the final gear in the drive train.

This means that a drive sprocket twice as large in diameter will make the tank drive twice as fast.

This fact illuminates the other incorrect claim you made, "When you use a larger diameter sprocket, you need to increase the track length to go around it. A longer track means faster tank speed."
For the same tank chassis, say 15 inches long, going from a 0.5inch sprocket to a 1inch sprocket won't increase the total track length by more than 2 inches, so by your reasoning you'd only see a speed increase of 2/15 or ~13%, when in fact this change will make the tank twice as fast. The tradeoff is that the tank will have half the amount of torque (and thus acceleration) at the ground, and will take longer to reach that top speed.

All of this is taking an unnecessary detour though, the track length itself is actually irrelevant. The drive sprocket in a tank functions no differently than the wheel on an rc car, and we know that at equal drive shaft rpms, a wheel twice the size will make the car go twice as fast. To convince yourself of this fact, imagine if you lowered or compressed the tank until the drive sprocket was in contact with the ground. Now the track is effectively just another layer of pavement, and the drive sprocket rolls without slipping along the ground, the same that a driven wheel on a car would.

Equations:
Motor rpm * gearbox ratio = drive sprocket rpm
(drive sprocket circumference / track length) * drive sprocket rpm = track rpm
track rpm x track length = rc speed.

Putting it together:
Motor rpm * gearbox ratio * (drive sprocket circumference / track length) * track length = rc speed.

notice how track length cancels out since it is in the numerator and denominator of the combined formula.

LEGO are you still an engineer at JPL or did you move over to Space X yet?

[LegoDEI]

The size of the sprockets do not matter. Here is the equations for calculating the 1/16 scale tank speed.

1. motor rpm x gearbox ratio = track rpm
2. track rpm x track length (inches) = actual RC tank speed in in/min

When you use a larger diameter sprocket, you need to increase the track length to go around it. A longer track means faster tank speed. It is simple mathematics. Please, let me know how my equations were wrong if you are not convinced.

Hi, I know this is a few replies ago, but I couldn't just read this and not correct it. You're completely missing a step in your equations. Namely, motor rpm x gearbox ratio DOES NOT EQUAL track rpm. Motor rpm x gearbox ratio gives you the drive sprocket rpm, which is NOT the same as track rpm.

Drive sprocket rpm converts to track rpm by the ratio of drive sprocket circumference to track length.
For example, a 1 inch diameter drive sprocket (3.14in circumference) will turn roughly 10 times for one full revolution of a 30inch long track. In this way, like SoCalBobS mentioned, the drive sprocket can be seen as the final gear in the drive train.

This means that a drive sprocket twice as large in diameter will make the tank drive twice as fast.

This fact illuminates the other incorrect claim you made, "When you use a larger diameter sprocket, you need to increase the track length to go around it. A longer track means faster tank speed."
For the same tank chassis, say 15 inches long, going from a 0.5inch sprocket to a 1inch sprocket won't increase the total track length by more than 2 inches, so by your reasoning you'd only see a speed increase of 2/15 or ~13%, when in fact this change will make the tank twice as fast. The tradeoff is that the tank will have half the amount of torque (and thus acceleration) at the ground, and will take longer to reach that top speed.

All of this is taking an unnecessary detour though, the track length itself is actually irrelevant. The drive sprocket in a tank functions no differently than the wheel on an rc car, and we know that at equal drive shaft rpms, a wheel twice the size will make the car go twice as fast. To convince yourself of this fact, imagine if you lowered or compressed the tank until the drive sprocket was in contact with the ground. Now the track is effectively just another layer of pavement, and the drive sprocket rolls without slipping along the ground, the same that a driven wheel on a car would.

Equations:
Motor rpm * gearbox ratio = drive sprocket rpm
(drive sprocket circumference / track length) * drive sprocket rpm = track rpm
track rpm x track length = rc speed.

Putting it together:
Motor rpm * gearbox ratio * (drive sprocket circumference / track length) * track length = rc speed.

notice how track length cancels out since it is in the numerator and denominator of the combined formula.

[keilau]

If the lower hull with tortion bar suspension is of sufficient quality, perhaps you could mate it with a heng long or trumpeter upper and Turret? Maybe both, even, if you have deep pockets? This is one area where building RC tanks is kind of like building muscle cars. Really nice tanks cost money, how nice do you want yours to be? That doesn't sound as cool as "Speed costs money, how fast you wanna go?", but I think you know what I mean.
😸

Heng Long markets an all metal M1A2 Abrams lower chassis if cost is no objection.

https://www.ebay.com/itm/234329197272?itmmeta=01HZDCQ58X31NZ67DPNEPCEC0D&hash=item368f1bcad8:g:CLgAAOSwdJNj1Pb~&itmprp=enc%3AAQAJAAAA4Eps%2Bi2SWb%2Fj3mxMXeO4ZyCWffvQMfwb1niH%2FXQHfP0cbTOnZiAjneqbdYTDKfJHOqZN53253wr2Op5YSiPKSX3qbBDqsebUOttycJ9lTfIVXyydUVCUSpl2wvX%2BKt5D2fZe3IWwXOfYT1LR5q5%2B72Qu8VpbCbmG1hnbD%2BgU4cJ1rWnVVot%2FQAUe%2FZoKrGqV8vpmoqZQw5UsrG6iguZKSqq7y3Bpr0rg9f2eARp4Q9LJq%2FAOQKQIXKe0f1dzXg%2F4ob8xWNywrvIRQ31%2FPLwLLse0%2FlmgFu3XxTcyh7JRh9%2BL%7Ctkp%3ABk9SR-7U3Kz7Yw

What I am looking for is an inexpensive 1/16 scale Abrams with torsion bar suspension and well fitted suspension arms. I hope that it has to scale sprocket and track so that I can use the Tamiya track on it. From the Tongde M60 upgrade experience, I hope that one of the TD Abrams can meet my expectations as an upgrade starting point.

[Max-U52]

If the lower hull with tortion bar suspension is of sufficient quality, perhaps you could mate it with a heng long or trumpeter upper and Turret? Maybe both, even, if you have deep pockets? This is one area where building RC tanks is kind of like building muscle cars. Really nice tanks cost money, how nice do you want yours to be? That doesn't sound as cool as "Speed costs money, how fast you wanna go?", but I think you know what I mean.
😸

[keilau]

The TongDE Abrams, from what I've seen from pics, has the worst scale details of any of the Abrams on the market including the Tamiya, the Heng Long, the Hooben, the Trumpeter static kits in 1/16, and even the Hobby Engine. It's your money though.

I am very disappointed to hear your comment. What I am looking for is an inexpensive 1/16 scale Abrams with torsion bar suspension and well fitted suspension arms. I have the Tongde US Patton M60A1 which met the above 2 expectations, but the track is completely off scale. Well, when I go for cheap, I can't have everything. My bottom line question is whether the Tongde RC Abrams looks like an Abrams. The Tongde Patton does not look like a Patton because of the extra wide track. But it is one of the best running tank in my small collection. I am surprised that there is not an aftermarket track/sprocket set that corrects the problem yet.

[tank_me]

Shantou Tongde post several 1/16 scale new tanks on their website, including 2 versions of Abrams with torsion bar suspension and several Shermans.

https://www.stplane.com/tank

The Abrams have made it to the Toucan Hobby China inventory. I have not seen an online review yet. I hope that Tongde would make the Abrams to scale so that I can use Tamiya tracks on it. Price is very good for a torsion bar suspension MBT.

The TongDE Abrams, from what I've seen from pics, has the worst scale details of any of the Abrams on the market including the Tamiya, the Heng Long, the Hooben, the Trumpeter static kits in 1/16, and even the Hobby Engine. It's your money though.

[keilau]

Shantou Tongde post several 1/16 scale new tanks on their website, including 2 versions of Abrams with torsion bar suspension and several Shermans.

https://www.stplane.com/tank

The Abrams have made it to the Toucan Hobby China inventory. I have not seen an online review yet. I hope that Tongde would make the Abrams to scale so that I can use Tamiya tracks on it. Price is very good for a torsion bar suspension MBT.

[Ziptar]

I've been following this thread and telling myself "No, Ziptar you are already 5 tank projects behind. You don't need another just yet." but I caved... Just ordered one from Banggood. For the price it's as cheap or cheaper than the static Classy Hobby kit and I'd be kicking myself later when they were out of stock or the price hiked.

It'll be a fun project to turn it into an M8 HMC or M8A1 tank destroyer prototype later on. I've already scheduled it for a Fender-ectomy!

[tank_me]

Welp, my Banggood order for Stuarts has shipped. Says it's slated for arrival on 7/11 so that sounds like the slow boat...

[keilau]

Speed is also a detriment on the real tanks which is the exact reason the Abrams is speed limited to 45mph. Higher speeds than that are bad for track life and track retention.

The 45 mph limit for US Abrams M1A1 is its highway transport speed limit. The Abrams battlefield speed limit is 25 mph for gas consumption consideration. Abrams has a gas turbine engine which is simpler, reliable and runs more quietly, but it is also gas Hungary. Only the US military can afford it and support the logistic. Cool war era tanks such as Patton, Pershing usually have 20+ highway speed. WW2 tanks were much slower due to track integrity consideration.

[tank_me]

Speed is also a detriment on the real tanks which is the exact reason the Abrams is speed limited to 45mph. Higher speeds than that are bad for track life and track retention.

[Handy Lance]

Speed is fun. My tank isn’t actually that fast on 3s, but it is a great scale unstoppable torque monster. But agreed, in these tanks there is to much wear associated with high speeds. Especially on suspension components.

[RichJohnson]

I really gotta say, while making an Abrams or leopard ludicrous fast is fun for a moment, like when I out ran Rubicons fastest tank with my prototype Leoaprd 1 drive, it was just insane to try and drive in anything but a straight line or a huge open field and quickly became boring and useless for any other kind of running or operation.
Speed also tends to cause you break parts, especially with the temptation to get airborne!

[SoCalBobS]

Sucker is too fast https://youtu.be/SDAUYGq6-ac?si=k78S2kJ-gDf3ccJx

Is that on the fast or slow mode?