Basic or am I Deluded ? 220-240V 2A DC motor speed control with no loss of torque

hi all, I'm new here and newish to electronics but its something i have been meaning to train in for some time, but now i have been forced in to getting with it a bit
I have a metal lathe good motor good working parts fried circuit board
replacement is about 300$Aus I am thinking of making my own circuit board to do the following tasks

Convert 240 AC (50-60Hz) to 220-240V
wire through to emergency stop and forward reverse (easy tasks the existing switches are working fine)
and the tricky bit (I think) having a speed control on the motor that does not loose torque as it spins slower

first glance at the current circuit board to my novice eyes looks way to complex for the task needed but what do i know maybe all the extra stuff is for the torque control

any input would be greatly appreciated

my other option is to replace all the faulty components but from the reading i have been doing its not an uncommon thing with this machine so i would rather bypass any future issues and change it now if its going to be possible and worth while

thanks in advance for any pointers

If you just reduce the motor voltage to reduce the speed, then you will also reduce the torque. To maintain torque you would need some method to control the voltage with a feedback loop from the spindle or motor speed that would control the voltage based upon the speed (to maintain constant speed).

Alternately if the DC motor has separate field windings, then you can control motor speed by changing the winding current (voltage). This will maintain the torque fairly well.

Do you know how the old board controlled the speed? How many leads does the motor have?

When the DC motor on my 1340 Smithy lathe/mill/drill went out it took the speed controller with it so I just refitted it with a used VFD unit and three phase motor and got rid of the DC motor and control system all together.

I think the used VFD and motor set me back less than $100 and are way better speed regulation than the DC system ever was.

Its just one option to consider.

Silicon chip did a good motor speed controller project last year, you can buy the kit from Jaycar. It is meant for AC motors but you can put a bridge rectifier on the output to feed the motor with DC.

Silicon chip magazine have a good website, you can ask them for details. I'm pretty sure I saw someone using the speed controller with a DC motor somewhere, maybe in their "circuit notebook" section.

awesome thanks guys

Crutschow - there are only 2 leads running from the motor a + and - oh and the earth lead to the case

Tcmtech - that was my other back up idea there is a good electric motor rewind place around the corner from work that i stopped in to today that seemed to have a nice large selection of refurbished motors so i may go back and price up what they could do for me to , they gave me the name of a place im going to visit in my lunch break tomorrow hopefully they can do what i want reasonably cheap

Mr RB - thanks i will check out their site tonight when i have a bit more time

ill let ya's know how i go tomorrow i basicly paid 60 for the lathe and just spent 40 on tools and a belt today at a cost price near on 800 i still ahve a bit to play with to get it for less than 1/2 price