Red or blue motors

[Rubicon99]

I measured the Pershing with Tamiya380 and Heng Xin gearbox to have scale speed of 26 mph. It does not sound too low. The HL T34 with red 390 and Heng Xin drives noteably faster, But I have not actually measure it yet. The Leopard 2A6 should be slightly faster than the T34 due to its longer Tamiya track, but far slower than the real tank speed for modern tanks. Unlike RC airplane or boat, measuring RC tank speed is very easy using basic engineering principle.

I am a backyard RC tank driver which means grass lawn mostly. I have not find a RC tank club in the Chicago yet.

Grass is hard on tanks almost as hard as mud. It causes a lot of maneuvering drag, likes to get caught in sprockets and break tracks. Tough to get the full feel of speed running on grass, but if its what you have, got to make the best of it.

26mph scale for a Pershing is actually pretty good considering the real ones were very rarely driven over 25 mph on road to keep from “blowing up” the transmission. I am assuming you tested the speed using a 2 cell 7.4v (~8.4v peak) Lipo. Push the power to 9.6v or slightly higher and you will easily be at 30mph scale (the maximum published road speed for a M26 Pershing). Using a 3 cell Lipo running on HP and you will be even faster. Used in short maximum power bursts HP should not hurt the MFU or motors. The 7.0 is rated up to 20 amps and 12v.

If you want to safely run 3 cell Lipo batteries for their added power output look at upgrading the MFU to the 7.1. It has a 180 amp and 12.6v rating which is the highest ever offered by HL and far more then even the new Tamiya DMD 11 systems. The 7.1 paired with a 3 cell Lipo battery would make it easier for you to achieve the overall speeds you are looking for.

[RichJohnson]

In actuality the Pershings were much slower than the Sherman’s despite their published speeds.
in the book “Spearhead” the tail of the Pershing and its crew that were in 3d Armored Division 32nd AB who took the city of Cologne, Clarance Smoyer the gunner in the Pershing whom much of the book was told by, recounted that once they were issued the Pershing it greatly slowed the columns’ road march speed so the Pershing could keep up. Having the same power plant as the Sherman in a much heavier tank didn’t work out so well. It’s remodeled M46 variant was quite a bit more powerful.

[keilau]

Grass is hard on tanks almost as hard as mud. It causes a lot of maneuvering drag, likes to get caught in sprockets and break tracks. Tough to get the full feel of speed running on grass, but if its what you have, got to make the best of it.

I found running RC tank on grass lawn can be fun when you get tough enough track which I do now. However, the clean up of track and wheels afterward is not fun. "but if its what you have, got to make the best of it." I have an 1/3 arca lot and the lawn with torrent making it a good RC tank running ground.

26mph scale for a Pershing is actually pretty good considering the real ones were very rarely driven over 25 mph on road to keep from “blowing up” the transmission. I am assuming you tested the speed using a 2 cell 7.4v (~8.4v peak) Lipo. Push the power to 9.6v or slightly higher and you will easily be at 30mph scale (the maximum published road speed for a M26 Pershing). Using a 3 cell Lipo running on HP and you will be even faster. Used in short maximum power bursts HP should not hurt the MFU or motors. The 7.0 is rated up to 20 amps and 12v.

When I drive the RC tank around, the RH stick is halfway up or down 90% of the time. I have enough open space to let them do an occasional straight line top speed dash which is fun to watch. Speed chasing is for RC buggy folks only. Tank is inherently clumsy and slow. I like Lithium-Ion battery for the RC tanks. Good cell keeps charge over longer time and a 2S pack stays at 8 volts during half of the discharge cycle.

If you want to safely run 3 cell Lipo batteries for their added power output look at upgrading the MFU to the 7.1. It has a 180 amp and 12.6v rating which is the highest ever offered by HL and far more then even the new Tamiya DMD 11 systems. The 7.1 paired with a 3 cell Lipo battery would make it easier for you to achieve the overall speeds you are looking for.

I have one 6.0s, two 7.0 and one 7.1 by default of ordering time. I tried a GoldBat 3S Li-Po with all MFU with no problem. The 70% low power setting is a nice feature. HL did a very good job improving the MFU over the year, but the transmitter quality is still terrible.

[keilau]

My personal dynamo for RC tank is a short piece of 2x4 to get the track off ground. I measure the track rpm with a handheld tachometer.

I get the tank model speed in inches/min by multiplying the track rpm with the track length. Then the model speed is multiplied by tank scale of 16 and unit converted to mph. It is very simple, straight forward arithematic. It does not take the road friction into consideration and may be on the optimistic side in value.

I developed this methodology to measure 380 and 390 motor temperature rises when there are so many melt down story around. The track rpm measurement is for me to monitor the battery condition during extended test time. Both worked very well and are very repeatable. In my recent posts, I made several mistakes on the derived scale speed due to my slopy estimate of the model track length and careless calculation. The track rpm were accurate and useable.

The HL M26 Pershing scale speed are 23 mph and 41 mph with 380 and 390 motor respectively. The HL German Leopard 2A6 are 28 mph and 50 mph.

For comparison, the Pershing had sustained speed of 26 mph and top dash at 30 mph. The Leopard sustained road speed is 43 mph. The model track length are 31.5" for Pershing and 38.5" for Leopard.

I hope that someone has the same tanks can use the AAF method to verify my calculation.

[oldwolf]

I developed this methodology to measure 380 and 390 motor temperature rises when there are so many melt down story around. The track rpm measurement is for me to monitor the battery condition during extended test time. Both worked very well and are very repeatable. In my recent posts, I made several mistakes on the derived scale speed due to my slopy estimate of the model track length and careless calculation. The track rpm were accurate and useable.

The HL M26 Pershing scale speed are 23 mph and 41 mph with 380 and 390 motor respectively. The HL German Leopard 2A6 are 28 mph and 50 mph.

For comparison, the Pershing had sustained speed of 26 mph and top dash at 30 mph. The Leopard sustained road speed is 43 mph. The model track length are 31.5" for Pershing and 38.5" for Leopard.

I hope that someone has the same tanks can use the AAF method to verify my calculation.

I like your technique because it takes up so little space. Where did you get your tachometer? My present method is to set up a marked, measured distance (just some strips of masking tape on the floor, 5 feet apart). Then run the tank through at full speed, while making a video of it at right angles using my iphone. Editing software lets me look at the video frame by frame and gives me the time each frame was taken. The key frames being when the nose of the tank crosses each line of tape. It is a bit complex, but way better than trying to control the tank with one hand, use a stop watch with the other hand all while trying to eyeball when the tank crosses each mark.

[RichJohnson]

[keilau]

I like your technique because it takes up so little space. Where did you get your tachometer? My present method is to set up a marked, measured distance (just some strips of masking tape on the floor, 5 feet apart). Then run the tank through at full speed, while making a video of it at right angles using my iphone. Editing software lets me look at the video frame by frame and gives me the time each frame was taken. The key frames being when the nose of the tank crosses each line of tape. It is a bit complex, but way better than trying to control the tank with one hand, use a stop watch with the other hand all while trying to eyeball when the tank crosses each mark.

https://www.ebay.com/itm/27488952021...Bk9SR5zNuOGQYQ
There are many US sellers for this cheap tachometer. It is very accurate and easy to use, but not very solidly built. I am using a second tachometer now. Dropped the first one on a concrete basement floor and it stopped working even the case looked fine.

My approach is a little indirect. I would like to see some comparison with your result.

[oldwolf]

https://www.ebay.com/itm/27488952021...Bk9SR5zNuOGQYQ
There are many US sellers for this cheap tachometer. It is very accurate and easy to use, but not very solidly built. I am using a second tachometer now. Dropped the first one on a concrete basement floor and it stopped working even the case looked fine.

My approach is a little indirect. I would like to see some comparison with your result.

The only tank I still have a video of doing a measured 5 feet at full speed is my Tamiya centurion, using a 7.2v Nimh battery and set to Tamiya’s lower power setting that they claim gives a reasonably correct speed for the model. I got 2.35 sec covering the 5 feet. If my math is right that is 23.21 mph. I believe the real tank did around 22 mph, so not bad on Tamiya’s part.

[keilau]

The track rpm cannot be used to determine the motor raw rpm because I do not know the ratio of track length to equivalent sprocket diameter. I built a simple test rig to test motor rpm, using a spare HL gearbox. The shape and diameter of the measurement wheel is not important. I just need to hold the tachometer red LED spot to the marker.

Using 8.0 volt Li-Ion, the HL grey stock 380 measured at 15,000 rpm. The grey 380 runs at 40°F above ambient. The 4 better quality motors all run 20 degrees or more cooler. The Mabuchi RS380PH-3270, Tamiya 380SP, HL Red 390 and MxFans 390 have rotational speed of 14,000, 17,500, 26,000 and 30,000 rpm respectively.

Any comment on my simple approach and comparison of data is much appreciated.

[cmdrcody]

Will the red motors replace the original motors in the stock steel gearboxes of the Russian T90 tank without any installation issues? My concern is that the original motors are snug against each other. So basically what is need to be known is if the diameter of the red motors is the same as the original motors? Or is it best to go to the blue motors?

[Rubicon99]

Will the red motors replace the original motors in the stock steel gearboxes of the Russian T90 tank without any installation issues? My concern is that the original motors are snug against each other. So basically what is need to be known is if the diameter of the red motors is the same as the original motors? Or is it best to go to the blue motors?

Red motors fit fine. I run them is all my T72/90s.

[cmdrcody]

Red motors fit snuggly. I run them is all my T72/90s.

What mAh size battery are you using to compensate for the extra draw from the red motors and how much run time are you getting?

[Rubicon99]

What mAh size battery are you using to compensate for the extra draw from the red motors and how much run time are you getting?

I removed all my T72/90 battery boxes to make room for 9.6v 5000 mah NiMH batteries. These are heavy and help add needed weight to the T72/90. I use NiMH because I seal the battery in, charge and store them in the tank. Not something recommend for Lipo or Li-Ion batteries.

Run time will vary based on how hard I am driving the tank but averages 30-45 minutes.

[cmdrcody]

I removed all my T72/90 battery boxes to make room for 9.6v 5000 mah NiMH batteries. These are heavy and help add needed weight to the T72/90. I use NiMH because I seal the battery in, charge and store them in the tank. Not something recommend for Lipo or Li-Ion batteries.

Run time will vary based on how hard I am driving the tank but averages. 30-45 minutes.

Well didn't know that the 7.0 MFU would handle that extra voltage thrown at it or even the speakers not blowing out. I'm not going as far as your method for powering the tank by modifying the lower case to except a larger permanently installed battery.
Did you ever run the red motors in your T90 with the Li-Ion 3.5A battery and if so how much run time did you get?

[keilau]

What mAh size battery are you using to compensate for the extra draw from the red motors and how much run time are you getting?

The HL grey 380, blue 380 and red 390 are basically the same in wiring, but different in finish quality and cooling fan. The grey 380 draws the most current due to the higher bearing friction. The blue 380 and red 390 are about the same and draw less current than the HL grey motor. The main difference between the blue and red is their rpm. The red offers more realistic scale speed for the T-72/90 For any HL configuration, a bonafile 3000 mAh or higher will offer decent performance and run time. You can check my posts on battery for more details.

[Rubicon99]

Well didn't know that the 7.0 MFU would handle that extra voltage thrown at it or even the speakers not blowing out. I'm not going as far as your method for powering the tank by modifying the lower case to except a larger permanently installed battery.
Did you ever run the red motors in your T90 with the Li-Ion 3.5A battery and if so how much run time did you get?

The 7.0 MFU is rated for 12.6 volts and well over a 20 amp draw. So you are even safe running 11.1v Lipos on the High Power setting. Although this will heat up the motors really fast.

I have not run my T72/90s or other tanks extensively on Li-Ion batteries, just have had no reason to. I usually stick to NiMH or LiPo batteries for tanks.

[tank_me]

[QUOTE=Rubicon99;n366234]

The 7.0 MFU is rated for 12.6 volts and well over a 20 amp draw. /QUOTE]

I'm curious if the amp draw is posted somewhere or where you got that info? I'm asking because I know the 160A for the 6.1 and the 180A printed on the 7.1 is a BS number. Supporting that many amps at 12.6V means it could support a 2000W motor and we all know that isn't the case.

[keilau]

The 7.0 MFU is rated for 12.6 volts and well over a 20 amp draw.

I'm curious if the amp draw is posted somewhere or where you got that info? I'm asking because I know the 160A for the 6.1 and the 180A printed on the 7.1 is a BS number. Supporting that many amps at 12.6V means it could support a 2000W motor and we all know that isn't the case.

The Mabuchi 380 series motor draws 2.28 amperes at maximum output and 14 amp at stall. A short duration (fraction of a second) 20A capability followed by a rapid shutdown will be a good design approach for Heng Long. Yes, the 160A for the 6.1 and the 180A printed on the 7.1 are BS numbers. In realistic operation, the plastic based, metal drive HL draws only a fraction of an ampere per motor.

[Rubicon99]

[QUOTE=tank_me;n366387]

The 7.0 MFU is rated for 12.6 volts and well over a 20 amp draw. /QUOTE]

I'm curious if the amp draw is posted somewhere or where you got that info? I'm asking because I know the 160A for the 6.1 and the 180A printed on the 7.1 is a BS number. Supporting that many amps at 12.6V means it could support a 2000W motor and we all know that isn't the case.

It’s been posted a few time since 2019 on this forum. Unfortunately I never kept track of which threads. Alpha when he was still active here posted the ratings. Alpha works or did work closely with HL on Motion RC behalf. Sadly I don’t think he is still with Motion RC, but he is one of the people largely responsible for the improvements we have seen in HL tanks since late 2018.

[SoCalBobS]

I'm ready to install some red motors in my Abrams and Challenger. Motion is OOS. Can anyone recommend a reliable seller of real 390's? TIA.