The purpose of this post is to tell a story which I hope will be of interest but also to ask for your help.
This is my Moretens H410 planer/thicknesser. I bought it new about 20 years ago. Made in Sweden, it was never a big seller in the UK and is no longer made following Moretens’ acquisition by WoodMizer. This is sad because it is a great machine with very good extraction, but no requirement for any conversion between planing and thicknessing – no tables to lift (and go out of adjustment) or extraction hood to move, all of which is a great timesaver.
But it isn't perfect. It has two related shortcomings:
View attachment Moretens PT-4.jpg
The root of the first is the long run of the poly-V belt which takes the drive from the main motor in the bottom of the cabinet to the cutter block at the top – there is a separate motor for the drive rollers. The distance between the pulley centres is 670 mm with no idler pulley to reduce the inevitable tendency for the belt to flap.
View attachment Moretens PT-6.jpg
The motor mounting doesn’t help. On the far side of the motor (as viewed in the photo) it is bolted at each end through a substantial stainless steel tube running from the front to the back of the cabinet. This tube can rotate sufficiently to allow the motor to drop down on the other side for belt tension adjustment. And that is the root of its other shortcoming; on this side, only one of the motor’s mounting holes is used via the green bracket which has a slotted hole where it mounts to the cabinet to provide belt tension adjustment.
Unlike traditional V belts, the poly-V variety are very intolerant of pulley misalignment. Pulleys must be accurately coplanar and similarly accurate in vertical alignment. If these requirements are not met, the belt will tend to jump grooves and may be thrown off altogether, and flapping will only increase the likelihood of this happening. On my machine, the “pull” of belt tension combined with the three point motor mounting had caused the bottom pulley to tilt so that it was no longer coplanar with the top pully causing the belt to jump grooves and foul the block mounting, Besides damaging the belt, the build-up of belt debris increased friction to the point where the induction motor’s 20+ years old capacitor struggled to start the motor.
View attachment Moretens PT-14.jpg
View attachment Moretens PT-15.jpg
My solution to these problems had three objectives. The first was to stop the belt flapping. A friend kindly donated these two 10mm wide sealed for life bearings; bolted to the cabinet side by side, they make a very satisfactory idler pulley. These are mounted on the outside of the belt run so as not to reduce the wraparound on the pulleys and on the return (non-drive) part of the belt run which is the most prone to flapping.
View attachment Moretens PT-17.jpg
The second objectives were to provide a rigid four point mounting for the motor to ensure accurate alignment of top and bottom pulleys. Finally, I wanted threaded adjustment for belt tension – almost any design that relies on a bolt sliding in a slotted hole will be difficult to adjust accurately. Where, as here, restricted access ensures that two hands are needed to apply downward pressure on the motor to achieve sufficient tension and another two are needed to lock off the nut and bolt there is plenty of scope for bad language and bleeding knuckles. A piece of 25mm square, 3mm wall thickness stainless steel tube bolted through the bottom flanges of the front and back cabinet panels proved to be plenty strong enough and extremely rigid. Bolting it rigidly in this way eliminated the original slotted hole tension adjustment, but long setscrews through the motor mountings and square tube provide fine screw adjustment via nuts above and below the square tube. Additional locking nuts underneath the motor mounting plate eliminate any possibility of motor “bounce”.
I am pleased to say that with everything bolted up tight the alignment errors had disappeared and the belt ran straight and smoothly when spun manually. When started, everything still ran straight and true, there was some flapping on the drive side of the belt, much reduced by increasing the tension a little.
However, a question still remains; how can I tell whether or not I have achieved optimum belt tension – clearly, I don’t want too much so that I compromise bearing life, but nor do I want too little. I have read that poly V belts require much more tension than old fashioned V belts and belt suppliers are only too willing to sell you an expensive tension measuring gadget. But I am reluctant to spend out on something I will probably only ever use two or three. I have searched the internet for a practical “rule of thumb” solution guide to this problem but without success. So, if any reader with practical experience setting poly V belt tension can offer guidance, I would be most grateful.
Jim
This is my Moretens H410 planer/thicknesser. I bought it new about 20 years ago. Made in Sweden, it was never a big seller in the UK and is no longer made following Moretens’ acquisition by WoodMizer. This is sad because it is a great machine with very good extraction, but no requirement for any conversion between planing and thicknessing – no tables to lift (and go out of adjustment) or extraction hood to move, all of which is a great timesaver.
But it isn't perfect. It has two related shortcomings:
View attachment Moretens PT-4.jpg
The root of the first is the long run of the poly-V belt which takes the drive from the main motor in the bottom of the cabinet to the cutter block at the top – there is a separate motor for the drive rollers. The distance between the pulley centres is 670 mm with no idler pulley to reduce the inevitable tendency for the belt to flap.
View attachment Moretens PT-6.jpg
The motor mounting doesn’t help. On the far side of the motor (as viewed in the photo) it is bolted at each end through a substantial stainless steel tube running from the front to the back of the cabinet. This tube can rotate sufficiently to allow the motor to drop down on the other side for belt tension adjustment. And that is the root of its other shortcoming; on this side, only one of the motor’s mounting holes is used via the green bracket which has a slotted hole where it mounts to the cabinet to provide belt tension adjustment.
Unlike traditional V belts, the poly-V variety are very intolerant of pulley misalignment. Pulleys must be accurately coplanar and similarly accurate in vertical alignment. If these requirements are not met, the belt will tend to jump grooves and may be thrown off altogether, and flapping will only increase the likelihood of this happening. On my machine, the “pull” of belt tension combined with the three point motor mounting had caused the bottom pulley to tilt so that it was no longer coplanar with the top pully causing the belt to jump grooves and foul the block mounting, Besides damaging the belt, the build-up of belt debris increased friction to the point where the induction motor’s 20+ years old capacitor struggled to start the motor.
View attachment Moretens PT-14.jpg
View attachment Moretens PT-15.jpg
My solution to these problems had three objectives. The first was to stop the belt flapping. A friend kindly donated these two 10mm wide sealed for life bearings; bolted to the cabinet side by side, they make a very satisfactory idler pulley. These are mounted on the outside of the belt run so as not to reduce the wraparound on the pulleys and on the return (non-drive) part of the belt run which is the most prone to flapping.
View attachment Moretens PT-17.jpg
The second objectives were to provide a rigid four point mounting for the motor to ensure accurate alignment of top and bottom pulleys. Finally, I wanted threaded adjustment for belt tension – almost any design that relies on a bolt sliding in a slotted hole will be difficult to adjust accurately. Where, as here, restricted access ensures that two hands are needed to apply downward pressure on the motor to achieve sufficient tension and another two are needed to lock off the nut and bolt there is plenty of scope for bad language and bleeding knuckles. A piece of 25mm square, 3mm wall thickness stainless steel tube bolted through the bottom flanges of the front and back cabinet panels proved to be plenty strong enough and extremely rigid. Bolting it rigidly in this way eliminated the original slotted hole tension adjustment, but long setscrews through the motor mountings and square tube provide fine screw adjustment via nuts above and below the square tube. Additional locking nuts underneath the motor mounting plate eliminate any possibility of motor “bounce”.
I am pleased to say that with everything bolted up tight the alignment errors had disappeared and the belt ran straight and smoothly when spun manually. When started, everything still ran straight and true, there was some flapping on the drive side of the belt, much reduced by increasing the tension a little.
However, a question still remains; how can I tell whether or not I have achieved optimum belt tension – clearly, I don’t want too much so that I compromise bearing life, but nor do I want too little. I have read that poly V belts require much more tension than old fashioned V belts and belt suppliers are only too willing to sell you an expensive tension measuring gadget. But I am reluctant to spend out on something I will probably only ever use two or three. I have searched the internet for a practical “rule of thumb” solution guide to this problem but without success. So, if any reader with practical experience setting poly V belt tension can offer guidance, I would be most grateful.
Jim
