# PM 1236/1340-T OEM Drive Belt Fragments



## gman10259 (Feb 26, 2018)

Anybody out there with the 1236/1340-T have any issues with the OEM Drive Belt? I have consistent small fragments coming off the belt when it runs. Has proper belt tension. I'm leaning more to a poor quality V-Belt as the culprit. What have you guys used as a replacement belt?


----------



## mksj (Feb 26, 2018)

Yep, stock belts stink. First thing one needs to do is replace them. I have been using the Gates Tri-Power belt, still on the same belt for 4 years with no discernible wear, belt imbalance or rubber bits flying all over the place. Since they are notched they tend to not take a set and handle the smaller low speed pulley better. You need to purchase both a BX-24 and a BX-25 (at least on the 1340GT), since the stock belt in somewhere in between the two sizes.  If you go to a VFD drive you can use a single pulley size/belt. Something in the 2.7-3.0" size and overspeed the stock motor to 90-100Hz.  I use an inverter/vector motor so rum my 1340GT to 1800 RPM using a 2.5" pulley with the motor at 125Hz.






Original motor





Inverter motor


----------



## Ray C (Feb 26, 2018)

Seems about normal.   Lot's of dust and clumped-up rubber in the first few months as best I can remember.  Power off, engage safties and check for alignment or possibly a burr somewhere.   If it all checks-out, tighten them up and check the next time you do a gear change.

As I recall, mine wore out after about 4 years and replaced it with an equivalent sized automotive belt.

Ray


----------



## SSage (Feb 26, 2018)

I have a PM1236 and it has dual belts, seems to be running fine. Belt dust looks normal to me after a few months of regular use. I'm glad it came with dual v-belts. I changed to the high range position and the belts felt good, not too hard. Maybe they will last a long time.


----------



## gman10259 (Feb 26, 2018)

Thanks for the feedback gentlemen.


----------



## gman10259 (Mar 10, 2018)

Well I tried Gates HiPower II B25 V belt (Made in Mexico) and had the same shaving issues. Then went with the Gates BX25 (Made in USA) and have had no belt shavings. Thanks for the advice *mksj. *I have the BX24 on order. *mksj* in the future I will also be putting a VFD and 3 phase motor on my 1236-T. What brand/size drive did you go with and what brand / spec motor did you use?

Thanks


----------



## mksj (Mar 10, 2018)

You will need to check the frame motor size dimensions, but I would replace the stock single phase motor with the Marathon 2Hp E467. The motor space is very small, so standard 145 frame TEFC motors will not fit, you need a TENV. Alternate 2 Hp motor is the the Marathon BlackMax and BlueMax Inverter motors, they have a small encoder shaft on the rear of the motor that needs to be cut off.  The pulley size depends on a number of different factors, the E467 has a usable speed range of approximately  20-90 Hz, maybe 100, so for a single speed you need something like a 3.0-3.2" pulley going to the larger headstock pulley.  The Y526 and Y551 I usually use 20-125 Hz running a 2.4-2.7" pulley going to the larger headstock pulley. You can measure the pulleys and do the calculations, but I usually work it out so at your maximum Hz, your spindle speed in high gear is ~1800 RPM.  The sock motor has a 3/4" shaft, the Marathon motors listed have a 7/8" shaft.

The Gates Tri-Power belts seem to work quite well, I have had no detectable belt debris spinning off since I installed them a few years ago. The notched belts work well around smaller pulleys.

I would buy a decent VFD for the lathe and run it in sensorless vector motor control, you will need a braking resistor.


----------



## gman10259 (Mar 10, 2018)

Thanks for the motor data. Are you saying I would need a braking resistor due to the regenerative energy being fed back into the drive bus or for assisting in stopping the spindle?

Thanks again for the advice on the gates BX belts. Hated the mess the regular v belts were making.


----------



## Bamban (Mar 10, 2018)

Gman,

Here is one of the earlier VFD conversions with Mark's control system. Did this on my Taiwanese 1236, could very well be from the same factory as yours. I used a Marathon motor, but very tight install, it has been trouble free though and I've used the lathe quite a bit.

https://www.hobby-machinist.com/threads/acer-trump-1236-vfd-conversion.32910/


----------



## gman10259 (Mar 10, 2018)

*mksj* did you put a speed pot onto your lathe's control panel or just running the vfd off its HMI?


----------



## gman10259 (Mar 10, 2018)

Thanks* Bamban*


----------



## mksj (Mar 10, 2018)

There is significant momentum in the lathe that will result in too much regenerative energy if stopped too quickly (like under 3 seconds but depends on the chuck and speed), the VFD will then freewheel to a stop. I use remote switches to control the lathe functions, along with custom panels for the control systems I build. Depending on the machine I will put the speed pot in the front control panel or in a small enclosure along with the RPM display. The VFD is usually in a separate enclosure that is sealed to keep out swarf, etc.


----------



## gman10259 (Mar 10, 2018)

*mksj *Thanks a bunch for the info, greatly appreciated.


----------



## gman10259 (Mar 10, 2018)

*mksj *like your control panel layout you do nice work.


----------



## wrmiller (Mar 11, 2018)

I still want one of those panels like Mark has. Maybe someday.


----------

