The slots do the daily work
On a belt drive, the motor base gets adjusted every time the belt is replaced or retensioned. So the slots are the feature that decides whether the base is good or just present. Slots are machined, deburred and lined with stainless shims on request.
We build bases for IEC and NEMA motor frames. Give us the frame size and we know the bolt pattern without asking.
The slot length sets the belt tensioning range. Too short and the fitter runs out of adjustment before the belt is tight. Too long and the motor overhangs the base and looks wrong. We size the slot to the belt spec, not to a standard.
Anti-vibration and alignment
Where the base sits on anti-vibration mounts we weld in the pad plates and check their height relative to each other, because a motor base with uneven pads gives the fitter a soft-foot problem that never really goes away.
Dowel holes for final positioning, jacking screw bosses for motor alignment, and lifting eyes on units above 100 kg all go in as standard practice.
On bases for motors above 75 kW the base is ribbed underneath the motor pad to stop the pad from flexing under the motor weight and torque. A flexing pad is another cause of soft foot that is hard to diagnose.
Special motor base designs
Some bases are not flat. A vertical motor base has the motor face down, and the base is a disc or a flange with a machined spigot. We build these too, with the spigot machined after welding to the motor fit tolerance.
For servo motors the base sometimes has a machined keyway or a pilot ring instead of slots, because servo alignment is tighter than a standard motor. The pilot ring is bored and fitted to the motor pilot dimension.
For motors in hazardous areas the base is built to the Ex requirements, which usually means no through-holes that could let gas into the junction box area, and the surface finish meets the temperature class requirement.
Product attributes
| Material | Q235B / Q345B carbon steel |
|---|---|
| Motor frames | IEC and NEMA bolt patterns |
| Slots | Machined and deburred, stainless shim strips optional, length to belt spec |
| Pad plates | Welded in, height-checked, ribbed under motors above 75 kW |
| Extras | Dowel holes, jacking bosses, lifting eyes above 100 kg |
| Special designs | Vertical motor flange, servo pilot ring, Ex-compliant construction |
| Finish | Shot blasted Sa2.5, anti-rust primer |
| Certificates | ISO 9001, ISO 3834, AWS D1.1 |
| Lead time | Samples 12 to 18 days, batch 25 to 40 days |
Frequently asked questions
Do you know the bolt pattern for my motor frame size?
For IEC and NEMA frame sizes, yes. Give us the frame size, for example IEC 132M or NEMA 256T, and we pull the foot bolt centers and hole diameter from the standard. For non-standard or custom motors, send the outline drawing or the foot dimensions.
How long should the tensioning slots be?
The slot length depends on the belt type and the center distance. A V-belt drive needs enough travel to slip the belt over the pulley plus tension it. A synchronous belt needs less because it does not stretch. We size the slot to your belt spec so you have enough adjustment without the motor overhanging the base.
What is soft foot and how do you prevent it?
Soft foot is when the motor feet are not coplanar with the base pads. When you bolt the motor down it twists, and the coupling goes out of alignment. We prevent it by machining the pad plates to the same height and checking coplanarity before the base ships. We also rib the pad under heavy motors so it does not flex under the motor weight.
Can you build a base for a servo motor?
Yes. Servo bases often use a pilot ring instead of slots, because the alignment tolerance is tighter. The pilot ring is bored to the motor pilot dimension after welding. Send the motor outline drawing and we will build to the pilot fit.
What about Ex-rated motors?
We build to the Ex requirements on the motor nameplate. That usually means no through-holes in the base under the junction box area, and the surface finish meets the temperature class. We are not an Ex-certified shop, so the certification stays with the motor, not the base.
Working with us
We are a 7,000 square meter fabrication shop in Qingdao with 20 years of export experience, mostly to Australia. Welding runs under ISO 3834 with welders qualified to AWS D1.1, and quality is documented to ISO 9001 from material certificate to final dimensional report. Drawings and specifications stay confidential. Frame size and drive type is all we need to start.
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