Spindle belt conversion

[Cad cam man]

To all ,
I have a PM727V and I have converted everything to cnc and after running it a while the brushless dc motor has gone out. I am swapping it out with a dmm 1kw servo motor and taking the high mid and low gears out and going belt drive . I am stuck at the pulley size I want it to have a high and low on ( large and small) diameter on the pulley but I dont what a good size would be . Does anyone know or have a pm728vt or a pm30 and can give me the size to the pulley??? Any help would be appreciated

 

[Eddyde]

I would try to determine what speed ranges you are trying to achieve and then calculating the pulley sizes. This site may help:

Pulleys and Belts - Inch

Visually calculate pulley size rpm belt length and speed wwith animated scaled diagrams - Inch

www.blocklayer.com

 

[GB21]

On the 728VT stock gearing is
Low speed 46/92mm or 2:1 pulley ratio
High speed 80/60mm or 1:1.33 ratio
Belt is a 180J5

A lot of variables come into play but using the online calculator above ^ is the way to go.

 

[C-Bag]

I would try to determine what speed ranges you are trying to achieve and then calculating the pulley sizes. This site may help:

Pulleys and Belts - Inch

Visually calculate pulley size rpm belt length and speed wwith animated scaled diagrams - Inch

www.blocklayer.com

Thanks for posting that! I found that years ago when I was trying to figure out the double reduction on my 14” bandsaw and could never find it again. It’s now on my homepage.

 

[Cad cam man]

On the 728VT stock gearing is
Low speed 46/92mm or 2:1 pulley ratio
High speed 80/60mm or 1:1.33 ratio
Belt is a 180J5

A lot of variables come into play but using the online calculator above ^ is the way to go.


View attachment 440284View attachment 440285View attachment 440286View attachment 440287

Wow thanks this is exactly what I have been needing thank you so much

 

[Cad cam man]

On the 728VT stock gearing is
Low speed 46/92mm or 2:1 pulley ratio
High speed 80/60mm or 1:1.33 ratio
Belt is a 180J5

A lot of variables come into play but using the online calculator above ^ is the way to go.


View attachment 440284View attachment 440285View attachment 440286View attachment 440287

Is there any chance I could get you to measure the overall length of each and thickness of the 80 mm diameter and the 92 mm diameter ? I want to get as close as possible to prevent belt tracking from the length being too long or too short

 

[GB21]

Is there any chance I could get you to measure the overall length of each and thickness of the 80 mm diameter and the 92 mm diameter ? I want to get as close as possible to prevent belt tracking from the length being too long or too short

Sure thing. Each pulley is 14mm thick or 28mm for the stack. The spindle pulley has a 3 mm boss on the bottom but obviously your machine is completely different. Are you going with a J section belt?

 

[Cad cam man]

Yes I am only because thats what everyone else has ....I have my doubt using the j section belt only because I will b tapping and I dont want it to slip causing the encoder to lose orientation. Do you rigid tap with your machine

 

[GB21]

No I threadmill everything. If you look at my most recent thread I just swapped to a 3 hp/2.2kw motor. I am using a 8 rib j Belt and have taken some beastly cuts so I don't think tapping would be a problem. I believe tormach uses 6 rib j belts and they rigid tap just fine.