Steve’s UC

[David Merritt]

Hi Steve, I have had it running and it has no problems on a hard surface either on the flat or up a 10 deg slope. On grass it has no problems going forward or reverse but is a little down on power when making tight turns, when it is effectively being powered by only one motor. I am looking at a motor with twice the wattage rating at the same r.p.m. which I think I have found, it is a 29T motor. The gearbox should be able to cope with the increase in torque.

I have replaced the single race bearing in the hub with a twin race bearing to reduce the possibility that load from the drive shaft put on the bearing of the gearbox. The original bearing is 8mm wide and the twin race bearing is 12mm wide and fits into the bearing recess well, as if it was made for it.

I have also used the mounting brackets supplied by MFA for the motors to provide protection to the motors, they form a flat surface that is just above the bottom of the carrier to which I have fitted an L shape pice of aluminium which is level and abuts the bottom of the carrier and rises up behind the motors to reduce the risk of ingress of dirt and dust into the motors.

David

[Steve Norris]

Hi David
Your set up sounds very good, please keep us posted when you get your new motor and gearbox.
The twin race bearings sound like a sensible idea as the set up I have at the moment is not ideal, I will upgrade mine when I get the chance.
Regards
Steve

[David Merritt]

Hi Steve, I received the 3S LiPo battery today and have run the carrier with the 27:1 ratio gearbox and 19.8W motor units. The battery was fully charged and producing 12v. The speed on a hard surface was faster than with the 2S battery, as expected, but the performance on the grass was no better than the 2S battery when attempting to turn. This indicates that the two 19.8W motors are not providing enough power to make a turn on a grass surface. I have some 51:1 ratio gearboxes with the same motors and I will try them with the 3S battery some time next week and see how well they perform. Effectively this should almost double the power available to turn the carrier on grass, the results of this will indicate how far I will have to upgrade the motors on the 27:1 gearboxes. They should be able to take motors up to around 80W without problems.
We will see. Watch this space.

By the way, the 3S LiPo battery is only a little wider and a little longer than the 2S battery so it fits in the back compartment of the carrier as the 2S battery and has a capacity of 5200mAh. Battery technology is advancing every year.

Regards

David

[Dennis Jones]

Hi David,

I think you will find the 50:1 gearbox better on torque but it is very slow even on 12 volts as I have already fitted a pair.

Dennis.

[David Merritt]

Hi Steve, I have been running the carrier with the 51:1 gearbox and a 12v battery. Yes Dennis it is a bit slow but having run it at that speed I am of the opinion that it would be fast enough for my grandchildren to play with it, but that is beside the point. There was sufficient power from the motor to enable it to run and turn successfully on the grass which indicates that a motor of not less than 40W is required to power the carrier and with careful management of the supply of the power to the motor, a motor of around 80W could be used and the 27:1 gearbox should be able to handle that power, so my next step is to install a larger wattage motor on the 21:1 gearbox.

The aluminium cover plate fixed to the gearbox mounting brackets supplied with the motors is working well at preventing dust, mud, stones, grass etc getting into the motors.

Regards

David

[David Merritt]

Hi Steve, must apologise for the long delay between now and my last post but life became chaotic there last three months or so. I have fitted the new motors to the 27:1 ratio gearboxes and installed them into the carrier and test run it. It runs well on a hard surface and has no problems running ot turning on the grass which is a little long as it has yet to be cut. The only problem I had was the track coming off the front idler on the left side when turning on the grass but there was no problem with my right idler when turning on the grass.

I will finish reassembling the carrier and then post some photos, it may be some weeks away as things are only just getting back to normal.

Regards

David

[David Merritt]

Hi Steve, i have completed the installation of the twin motor drive and have attached some photos.
The motors installed are 80W each, where the originals supplied with the gearboxes we 20W each, which have sufficient power to drive the carrier over most surfaces. I have only tried it on level grass so far with no problems manoeuvring at any speed. I have sorted the problem of shedding the track off the front idler when reversing and turning by looking the track warping system.

Regards

David

[Steve Norris]

Hi David
Glad to hear you sorted the track shedding problem out, I have removed the track warping system from my UC and locked the shaft centrally. The 80 watt motors should give loads of power, just hope the gearbox can take it.
Regards
Steve

[David Merritt]

Hi Steve, the motors produce 80W at 8.4V but the ESC that i am using allow me to restrict their maximum voltage output, which I have set at 75% znd as wattage is proportional voltage, this reduces the power to a maximum of 60W. The speed of the motors at this voltage is around 13000 r.p.m. which gives the carrier a scale spread of about 30 m.p.h. which was around the maximum speed of the carrier. The motors will only produce this maximum output when the movement of the carrier requires it, which should not been very often. The ESC also allow me to control the rate of acceleration from a standing start which again reduces the risk of blowing the gearboxes when starting the carrier moving.

I have had no problems so for. Long may it last.

Regards

David

[David Merritt]

Hi Steve, I thought I would let you know that because the tracks have been on and off my carrier so many times I am using a 40mm brass panel pin in each track to enable quick removal of the track. I have had no problems so far with excessive wear to the pin or any problems with it working its way out whilst running the carrier, and as it is brass there are no corrosion problems.

Regards

David

[Dennis Jones]

Hi David,

Can you email me details of motor supplier etc please. djones4990@gmail.com

Dennis.

[David Merritt]

Hi Dennis,

I went to Hobbyking and found trackstar brushed motor 550/21T. As you have probably found it is almost impossible to find the motor power rating, they provide the r.p.m and voltage information in one form or other but very little else.

Regards

David

[Dennis Jones]

Thanks David.

[David Merritt]

Hi Steve,

Have been running the carrier over rough ground and up and down grassy hills to see how the motors and gearboxes will perform. I have increased the voltage to the full voltage of a fully charged 2S LiPo battery with initially no problems but making sharp manoeuvres the drive on one side failed. It would still run in a straight line but would not turn.

Upon investigation it was found that the 2mm roll pin that was transferring the power from the gearbox to the drive wheel had sheared causing the failure in drive, thus protecting the gearbox from damage. I am happy with this as it is easier and cheaper to replace a roll pin than a gearbox.

There is plenty of power and speed with the current setup, I just have to be careful when using full charged 2S LiPo batteries (8.4v) on rough surfaces as it is close to or beyond the sheer limit of the 2mm roll pins.

The other area of caution is in making tight turns where one track rotates forward and the other backwards, it is causing a rapid change in direction of one track which is imposing a heavy load on the 2mm roll pin as the track is moving one way and the motor has reversed trying to make it run the other way.

Regards

David


Regards

David

[Steve Norris]

A little update on my carrier,
I have decided to go with a twin motor set up driving through 90 degree gearboxes ( there is no gear reduction with these boxes).
Originally my intention was to use 2 of the Armortek motor/gearboxes running at 12 volts, unfortunately the motors didn’t like this and I managed to burn on out. Next option was 2 MFA motor/gearboxes pt no 942D271 running on 12 volts, these are 27 to 1 reduction motors and hopefully will give a reasonable amount of torque and speed.
I have so far bench tested them and all seems good, just need to get my radio set up so that there is no neutral steer and then try a run outdoors.
Will keep you posted on the outcome.

Everything fits neatly under the engine cover.

Regards
Steve