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Hi; I have fitted my 36v forklift motor directly to the diff instead of through the gearbox as formerly. It works but does not have the same range or speed 4.2k @40kmh. I am using the same FLA junkyard batteries . The forward rotation is now opposite as to when in the forklift. Suggestions?(helpful and not crude, please)
 

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If it is a series motor it will/should have four connections to it. two of these will be to the field coils and two will be to the armature.

Normally you would connect one end of the field to the supply, the other end of the field to one end of the armature and then the other end of the armature to the supply.

The field and the armature are in series with each other, hence the name of the motor type.

To reverse the direction disconnect the field connections and swap them over with each other.


Coupling the motor to the diff instead of to the transmission will affect the performance of the car. This is because the gear ratios have changed and may not be suitable for the torque/power curve of the motor. It is one reason why most people keep the transmission intact even though only tow or three of the gears are used and infrequently at that.

The slow acceleration may be because the ratio is too high for the motor to be able to pull, it may not have the torque.
The lack of top speed may be because the ratio is too low, hence the need for a selection of speed.
Also it will depend on the voltage and controller set up too.

The loss of range may be because your motor is now pulling high amps at low rpm, where it is less efficient, when you are trying to move off. This is again down to not having gear ratios to allow the motor to spin faster when it is under load and to keep spinning at high speed as much as possible regardless of road speed.

Someone with more experience may come along and talk you through the rest.:)
 

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Thank you for your reply. This is the same motor that was in my hillman but without a gearbox. The diff ratio is very high; 3.7:1 and I agree with you that it does need to draw more amps. Do the brush settings affect it? If they were slightly advanced before now they would be slightly retarded; or is it unlikely that this would apply to an industrial motor? (St Marys Cray brand; series with the 4 leads as you described; C1970)
 

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So is the motor turning the other way to the Hillman installation or is it just turning the wrong way to what you need?

If it needs to still turn the same way as before then any advance will be as effective and you just need to rewire the connections.
If it turning the same way as before but needs to be reversed then the advance becomes retardation and that will need to be adjusted.


What voltage are you running at? If it is only 36v you don't really need to advance.
The loss in range could be very noticable if it is drawing high ams by running slowly most of the time and also if the timing is not neutral for slow speed and low voltage.
 

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Thank you for your reply. This is the same motor that was in my hillman but without a gearbox. The diff ratio is very high; 3.7:1 and I agree with you that it does need to draw more amps. Do the brush settings affect it? If they were slightly advanced before now they would be slightly retarded; or is it unlikely that this would apply to an industrial motor? (St Marys Cray brand; series with the 4 leads as you described; C1970)
yes, it needs to be advanced the other way now, if the "main" (forward) direction of rotation is now the other way. as posted above, the advance in the wrong direction slows it down a lot.
 
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