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Saving my Elu Belt Sander from the Grim Reaper

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Yojevol

Wooden tit be nice... ♪♪♪♪♪♪
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This is a metalworking project on a woodworking tool, so I hope it's posted in a suitable forum

My old Elu MHB90 Belt Sander is a bit of a beast to use and after 15mins or so sanding down an old oak dining table (more of that in a later post), my arms were in need of a rest and my head a coffee. On switching off the machine I noticed a wisp of smoke emerging. So after downing the coffee I decided it would be wise to discontinue the sanding and have a look inside. I stripped the whole machine down as far as I could:-
IMG_0022.jpg


I concluded it was just bunged up with years of accumulated dust and had overheated due to lack of airflow. So, clean it up and reassemble. All went well until refitting the drive belt.......SNAP. Oh dear – or words to that effect.
Abandon workshop. Get on the Net and find a replacement.
Problem – this sander came in 5 versions and toothed belts are only available for marks 4 & 5. There is no telling on the machine's label which mark mine is. Anyway, a spares supplier agreed to send me a belt, returnable if not correct. It came and went straight back! Tried a few other suppliers – same story.
Back on the Net. Could I find a generic belt that would do the job? No, the tooth form is obsolete.
Any other possibilities? I found that I could get a Poly-V Belt that would do but that would mean modifying the pulleys. In fact I would have to make them larger as the chosen belt was a bit longer than the original.
A quick chat with my mate Bill who just happens to own a very nice Myford 7. Yes – Game on. Ordered the belt and a lump of 3” dia ali. Opened up my TurboCad software and designed the pulleys to give the same ratio as the original:-
pullies.JPG


Not an easy matter as all the parameters are fixed apart from the pulley sizes. However after several iterations and a lot of design info from [url=http://www.powerparts.it/contitech_pdf/CONTITECH_multirib.pdf]this document[/url] I was ready to start cutting metal.
Stage 1, cut away the teeth:-
IMG_0032.jpg

to leave clean surfaces to take new sleeves (sorry about the focus):-
IMG_0034.jpg


Stage 2, Machine sleeves:-
IMG_0035.jpg


Ready for assembly using Loctite:-
IMG_0036.jpg


Stage 3 Machining 8 grooves
Some very accurate tool positioning required. The grooves are on a 2.34mm pitch. There was a complication here in that the design was metric but the Myford is imperial. What's more , the travel leadscrew has a 0.125" pitch and its position indicator is divided into 100, ie, 1.25 thou. so I had to convert all my dimensions accordingly. It was very easy once I got it sorted in my head:-
IMG_0037.jpg

IMG_0038.jpg


Stage 4 Reassembly:-
IMG_0039.jpg

I'd been apprehensive about putting it back together. Had my calcs been correct? Was my machining accurate? Would I be able apply enough force to stretch the belt by 1mm and at the same time get the pulleys on to there respective shafts? In fact it was very easy as the shafts had been cleverly designed such that the small pulley could be partially assembled prior to the large pulley being located. Both were then seated down by inserting their retaining screws.

Stage 5 Power up.
Yes it runs beautifully

Stage 6 Modify the plastic cover
IMG_0041.jpg

Unfortunately the belt now fouls the inside of the plastic cover. I'm planning to chop off the pulley/belt section and replace it with a brass fabrication. Materials ordered. Watch this space.....................

Brian
 

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Inspector

Nyuck, Nyuck, Nyuck!
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Nice repair that most would never bother with. If you could find a friend with a 3D printer a new guard would be relatively easy but polished brass would be eye candy.

Pete
 

Lons

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Great save! =D>

I'm ashamed to say that I binned my old Elu MHB 157E only a few months ago and I think it used the same toothed belt as yours, sods law if it did.

The motor had died and I held on to it for years wanting to fix it but just wasn't economical when I could buy a big new Makita for about the same cost.

We sold loads of Elu Swiss made power tools to industry and they're well worth hanging on to as the quality was superb, only went down hill when B&D eventually owned them and cheapened the manufacturing process and materials.

I still have a rather tattered instruction manual and a sanding plate attachment for the MHB 157, why I kept them is anyone's guess. :oops:
 

Yojevol

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Unfortunately the belt now fouls the inside of the plastic cover. I'm planning to chop off the pulley/belt section and replace it with a brass fabrication. Materials ordered. Watch this space.....................
Well time has moved on and 20 months later I find I actually have a need to use the sander. So to complete the job I needed to cut the plastic cover into its 2 components:-
20200906_163420.jpg

I then fabricated a new pulley/belt cover out of 2mm and 0.5mm brass sheet. Ordinary solder used:-
20200906_163442.jpg

Joined to the plastic fan cover with 5 self-tappers:-
20200906_163934.jpg

All tidied up, painted and fitted to the machine and ready to use:-
20200910_163505.jpg

Job done (at last)
Brian
 

Phill05

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Well done, pleased to see you have made a brilliant job of repairing it, I have the Elu little brother 3" wide and dropped it broke the tension bracket I made a new one rather than throw it away lasted me 25+ years now.

Phill
 

Cabinetman

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That was quite a bit of work to fix that, but a good machine is worth saving. I’m still using my shuffle Elu for decorating and polishing, hell its 40 years old!
 

Yojevol

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Having used it for the first time a few days ago, I'm finding that the new belt is getting very hot even without the cover on. I need to talk to the supplier or manufacturer (Dunlop)to see if this is normal. It may be that it needs to loose its stiffness. Also the small pulley diameter is on the acceptable limit for this belt so it's on its maximum flex.
Brian
 

Eric The Viking

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Do you have a really soft pencil (4B or softer). I would try lubricating the pressure plate. I do this with mine (smaller, modern Makita) and it seems to help. I have spare plates for it, and new ones start off all silvery & shiny, but actually get blueing and scorchmarks after a while, never mind grooves in them. They must get pretty warm.
 

Yojevol

Wooden tit be nice... ♪♪♪♪♪♪
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Do you have a really soft pencil (4B or softer). I would try lubricating the pressure plate. I do this with mine (smaller, modern Makita) and it seems to help. I have spare plates for it, and new ones start off all silvery & shiny, but actually get blueing and scorchmarks after a while, never mind grooves in them. They must get pretty warm.
Sorry I'm referring to the new drive belt
 

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