Hi I have just obtained a MHB90 Type 4 Belt Sander and the motor seems to be seized. I took the main drive belt off and the rollers are quite free. I would like to dismantle the motor to see if there is anything jammed in it. I am uncertain as to how to remove the small drive belt pulley to allow me to split the casing. Any help would be appreciated. The handbook does not show this level of maintenance. Thanks Ivor
Not familiar with that bit of kit, but with many motors you can dismantle from the non-drive end even if it leaves you with the rotor trapped in the drive end bearing housing by the pulley. At least that lets you look at the insides.
Here's a link to a blow-up drawing of the MHB90 from the Miles website
Miles carry spares for most of the later Elu power tools among others
michael adams
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me to split the casing.
Hi Thanks to those who replied.
Michael, thanks for your suggestions. I had actually downloaded the information from the site you mentioned to ge t a spares listing; the Plate at '105' is in need of replacement. It would seem that the motor housing has to be dismantled from the gear/out put end of the shaft. Item '60' would have to be unscrewed from the shaft using some sort of spec ial spanner that fits on its toothed belt splines. The motor shaft has a sl ot in the end to allow you to hold the shaft, with a screwdriver I presume, whilst you screw the splined item off using the special spanner. Nut '159' is encased in the splined area so there is no way of getting a gr ip on it. At least that is how I read it; I could be wrong, but I don't think that us ing a puller to remove item '43' would be a good idea, as this part with co oling fins is made of soft plastic and anyhow there is no clearance for the puller fingers in at the centre.
Yes Newshound if I was able to dismantle from the non-drive end, I could se e just what is causing the seizure; it is locked totally solid. I removed the brushes and there is no evidence on anything amiss in there.
I'll keep the thread open, in case someone has been there and got the t-shi rt. Thanks again Ivor
Sorry if I was stating the obvious.
If nut 159 is encased by the fan / belt pulley 60 that suggests that the two parts must screw off together. If that is the case, I would be inclined to wrap the "splines" in a reasonably number of turns of PVC tape to protect them, then grip them firmly with a mole wrench and try to unscrew it. If motor turns clockwise when viewing the nut it is likely to be a left hand thread.
w me to split the casing.
o get a spares listing; the Plate at '105' is in need of replacement.
/output end of the shaft.
special spanner that fits on its toothed belt splines. The motor shaft has a slot in the end to allow you to hold the shaft, with a screwdriver I pres ume, whilst you screw the splined item off using the special spanner.
a grip on it.
t using a puller to remove item '43' would be a good idea, as this part wit h cooling fins is made of soft plastic and anyhow there is no clearance for the puller fingers in at the centre.
d see just what is causing the seizure; it is locked totally solid.
I would like to do that but the spline material looks to be an alloy and no t steel and I would be concerned about splines breaking off. Item 60 is not listed as a spare, so cannot be replaced if damaged. The alloy part/splined drive part of 60 shown next to nut 159, looks to be separate from the actual larger black plastic part which contains the cooli ng fins. The 2 parts of 60 could of course be molded together. I cannot apply any form of heat because of the soft plastic. I'll have another look at it and maybe try your method. There might even be splined spanners for the job; I'll ask some of my engin eering friends.
Don't worry about stating the obvious, I can look at something and still no t see the obvious. Anyhow thanks for the prompt response. Regards Ivor
I think you are being a bit "nervous" (given that it is currently "dead"). Whilst factories *might* have special spanners for assembling these pulleys I have never seen one. With about ten turns of PVC tape on the pulley and a mole wrench with curved jaws the load should be distributed over several splines on each side, and will be limited by the yield strength of PVC and I would expect it to unscrew without any trouble. There is a certain "feel" in using a mole wrench in this way, It wants to be tight enough but not too tight. Alternatively you could drill a suitable piece of wood or plywood to close to the pulley OD (ideally a bit below) then cut it in half, remove a bit more material, and use this as "soft jaws" in a vice (or a big mole wrench) to clamp the pulley.
Another thing you might consider is to use the old drive belt as a "strap wrench", that way you can put a significant torque on the pulley while spreading the load over a good number of "splines". Again, a mole wrench is one easy way of doing this.
to be seized.
low me to split the casing.
to get a spares listing; the Plate at '105' is in need of replacement.
ar/output end of the shaft.
f special spanner that fits on its toothed belt splines. The motor shaft ha s a slot in the end to allow you to hold the shaft, with a screwdriver I pr esume, whilst you screw the splined item off using the special spanner.
g a grip on it.
hat using a puller to remove item '43' would be a good idea, as this part w ith cooling fins is made of soft plastic and anyhow there is no clearance f or the puller fingers in at the centre.
uld see just what is causing the seizure; it is locked totally solid.
d not steel and I would be concerned about splines breaking off.
be separate from the actual larger black plastic part which contains the c ooling fins. The 2 parts of 60 could of course be molded together.
ngineering friends.
l not see the obvious.
I wouldn't say I was nervous, I was just being cautious and wanted to give it a little more thought before jumping in and perhaps damaging the splines . In the end, I decided to use 5mm hard pins, and placed them in the 16 groov es of the splines and THEN taped the whole lot up using 15-20 turns of PVC tape as you suggested. This meant that the pins fitted snugly in the groove s and using water pump pliers, I was able to grip the pins not the cast all oy splines and remove the assembly from the motor shaft. It turned out that foreign plastic material had somehow entered the motor a ssembly and with friction/heat had attached itself to the plastic impeller and the bearing thus causing a complete seizure. All is now running free; I just have to clean the complete unit, replace Pl ate '105' and Cork Pad '103', both on order and finally reassemble the sand er. Thanks for all help offered. Regards Ivor
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