Woody – Page 35 – Woody's Workshop

October 23, 2020

BK3 Burgess Bandsaw motor drive shaft pulley replacement

A Potential JSN Job with a Hidden Benefit

Since publishing details of the blade guide modifications on the Burgess BK3 bandsaw I have received a lot of interest and also a request for a replacement motor shaft pulley and a replacement blade drive pulley.

After dismantling my machine to check the dimensional details I discovered that the red plastic motor shaft drive pulley on my BK3 was severely worn to the extent of the teeth looking very distorted. (See image below). It would appear I need a new pulley also.

For those not familiar with the BK3 genre, the red drive wheel is a sliding fit on the motor shaft and has a helical slot in the end which locates into a cross pin through the motor shaft. The gear wheel is forced tight into the slot by virtue of the direction of rotation during cutting. Reading the handbook for the BK3 it seems that this pulley is designed to slide off to allow it to be swopped with an eccentric pulley mechanism when the BK3 is used as a fret saw.

The drive belt on the BK3 is 9mm wide and 5mm pitch (with 102 teeth). The red pulley has teeth extending axially over 25mm. This is to allow the one pulley on the motor shaft to drive two different pulley diameters on the blade drive pulley with only a change in belt length. This gives two blade speeds of 106m/min and 396m/min. My BK3 never had the second pulley combination when I bought it second hand. The BK3 is a well thought out machine and despite its vintage is very popular and commands relatively high prices on EBay etc.

Back to the plot.

My first instinct was to 3D print a replacement red pulley and this was successfully done using the Fusion 360 gear wheel design script. Rather than trying to model the helical slot I opted for a simpler solution of a pair of diametrically opposite ‘L’ slots. This worked well as a concept when trialled on the 3D printed version.

Rather than ship a PLA version to the client I opted to modify a standard off the shelf 14 tooth x 25mm wide x 5mm pitch pulley. These are available from Bearing Boys (14-5M-25). The one slight problem is that the boss on the pulley needs to be drilled out to 9.5mm to match the BK3 motor shaft. This does not leave a lot of meat on the boss. To get the best possible strength from such a modification I opted for a steel pulley rather than aluminium.

First operation is to drill out the centre bore of the pulley. The motor shaft appears to be 3/8″ (0.375″ or 9.5mm ish). I incrementally drilled the centre bore upwards from 5.5mm to 9.5mm but the pulley was still reluctant to slide onto the motor shaft. Not having an adjustable reamer I ended up using a letter ‘V’ drill to get a closer fit and then a light skim with a boring bar. After the shaft had been cleaned this combination gave a nice sliding fit

The red plastic pulley had a tooth width of 25mm. The teeth on the bought in steel pulley are wider (~28mm). The red pulley only has the single outside belt retaining collar. On this basis I gripped the boss end of the pulley in a collet and turned back the teeth width by 3mm. Note there is one slight problem. The belt retaining collars are not an integral part of the steel pulley casting but a thin dished additional fitment. The result is that at some point in the turning this fitment starts to rotate independently of the pulley body and I had to use the Dremel to cut this residual ring free before I could continue.

Having reduced the teeth width to 25mm, the ‘L’ slots need to be cut. I cross drilled the pulley boss with a 3.5mm hole. I then rotated the pulley in the mill jaws by a few degrees and then cut a diametric 3.5mm slot axially down to the same level as the 3.5mm hole and then hand filed the break through from the slot into the hole to create a retaining notch. The pulley bore was then cleared of any induced burrs.

The pulley now pushes onto the shaft and with a twist anticlockwise, the shaft cross pin locates into the ‘L’ slot notch.

BK3 motor drive pulley replacement — Top image is a dimensional sketch of modifications to the standard off the shelf pulley. Lower image shows the new black pulley with a ‘L’ locking slot and the original red pulley. Note the wear on the original pulley and the helical locking slot.

So far so good. Next job is to recreate the large drive wheel pulley.

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September 8, 2020April 16, 2021

Burgess BK3 Bandsaw Disaster and Repair

Some pieces of workshop equipment generate a sentimental attraction that is hard to break. One such piece of kit is my Burgess BK3 bandsaw which is ancient but has up to now worked reasonably well for my needs. I bought it on EBay from an owner in Lancashire and remember a nice day trip to collect it.

It is a very useful machine and gets pressed into use day in and day out. That is until the other day when the blade came off with a loud twang. On inspection the drive wheel had lost part of its blade outer retaining flange. It appeared to be very old brittle plastic and the damage was really to be expected given the vintage of the device.

After head scratching I designed a replacement edging strip in Fusion 360 which I 3D printed and glued in place. Fingers crossed that will give the machine a reprieve and extend its life.

In the course of looking for possible spares (no chance) I came across a reference to modifications to the BK3 in Model Engineer to improve the blade tracking and speed settings. Here is a link to the articles burgessbandsaw2. I am indebted to the members of my local model engineering club who came up trumps with copies of these articles for me.

The guide modification consisted of replacing the two stud guides with ball bearings. While the machine was in pieces it seemed like a good idea to implement this modification. The Fusion 360 3D model is shown below. The blade is sandwiched between the two ball races and these can be slid in and out and then be fixed in place with the cap head screws once the correct location is found to guide the blade.

I drew the replacement guide block assembly in Fusion 360 and milled it on the Tormach CNC from brass. The 1/2″ bearings came from BearingBoys.

All is now re-assembled and running really smoothly. The blade prefers to run in straight lines which is a revelation.

Update : Since this blog entry I have made other modifications to my BK3 and these are contained in this link BK3 Modifications v2.

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September 8, 2020January 21, 2022

Clough42 Electronic Leadscrew Project Implementation Notes

I have been avidly watching Clough42 on YouTube. James comes over as a really nice guy and his presentation of his projects is excellent.

My principle interest is the Electronic Leadscrew modification to lathes. When installed this removes all the hassle of gearboxes and look up tables to be able to cut both Imperial and Metric screw threads and to set X axis movement feed rates.

The concept is simple but his implementation is second to none. A rotary encoder is fitted to the spindle to count revolutions of the chuck and a stepper motor (or servo hybrid) controls the rotation of the leadscrew. The resulting feed speed is derived from look up tables. The whole installation is controlled by a Texas Instruments LaunchPad C2000 microcontroller development board.

I have documented how I implemented this on my Myford Super 7 Big Bore lathe and the pdf can be downloaded below. There is also a ZIP file of all the Fusion related models for either CNC or 3D printing.

Electronic Leadscrew on Myford Super 7

Minor edits added to v3 relating to programming the servo controller

Electronic Leadscrew on Myford Super 7 v3

Electronic Leadscrew Fusion 360 Files

Updates : –

Painted control panel for Clough42 Electronic Leadscrew — Finally got the Clough42 Electronic Leadscrew control panel box painted and rather pleased with the result.

Since installing the ELS I have incorporated thrust bearings on the leadscrew mounting. This impacts on the coupling to the stepper motor.

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August 23, 2020August 23, 2020

Windows 10 Upgrade and another day dribbled away through my fingers

We are sitting in quarantine and now on Day 5. Not really any different to how we were before we went to France and when we were in France – just different jobs around the house and workshop and zero outside contact other than food deliveries. (My wife gets very excited at the prospect of seeing the deliveries arrive).

I got fed up with the boot warnings on Fusion 360 that Win7 would not be supported so I decided that I would upgrade to Win10. My machine is fairly well spec’d so there was no great desire to upgrade to a new machine. It was i7 based and had 32MB of memory with a 250GB SSD and a 1TB secondary drive. Both drives were pretty full and into red warnings so I bit the bullet and opted for a clean load. I bought in a new 500GB for the operating system and app storage and a massive 2TB data storage secondary drive. Total cost under GBP100 which is staggeringly cheap.

Changing the hardware was simple. I bought in a SATA to USB dongle to allow the old drives to be available for data transfer and this made life a bit easier.

Loading Win10 and all my favourite apps took over a day. It is just never simple. Finding software keys is always a bit of a problem as some apps hide it away in Registry. Finding EXE loading files is another frustration. Why when you buy an app do some providers send you an email link to download direct with a licence key ? This results in nothing showing in ‘Downloads’ history to refer back to and reload the app. When you try to use the old email link it downloads the latest version and tells you that your licence key is no longer valid. When you go to their site the version that did everything you ever wanted has been upgraded and needs you to pay to now use the later version. ‘Hello .. I have paid for version X and I don’t want to pay for version Y thank you very much. Just give me a download link to restore what I know and love”. Rant over on that one.

Some weird effects on Outlook transpired. I have a GMail IMAP account and three POP accounts all loaded on Outlook. After loading I had an extra ‘Sent’ folder on the GMail folders tree which contained the Sent items from one of the POP accounts. Spent a lot of time on this and didn’t satisfactorily solve it other than deleting the contents from this duplicate folder. The messages are still there in the POP folder so not sure what that was all about.

My 3DConnexion Spacemouse loaded across fine onto Win10 but I still had a related exception error window coming up on booting the machine. This was the same as it had been on Win 7 so clearly something was common mode. I could click it and the message window would disappear but it was annoying. After some digging I traced it to Trend Antivirus. If I put the two 3dconnexions’ Windows folders into Trend as ‘Ignore’ items it all went away. Progress on that one.

So I think I now have a (mostly) stable Win 10 machine. I hate all the nanny state Windows ‘fluff’ that stops you getting quickly to things such as System\Hardware like it was in XP. In an attempt to ease this I have loaded Stardock’s ‘Start 10’ which mimics the old style Start menu and this makes me feel a bit more familiar.

Hopefully this was all worth doing and things will now go swimmingly along with no crashes and dramatic improvements in productivity …. gosh were those really pigs I saw flying past ?

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August 20, 2020

France visit with astro photography and Canon camera CHDK hack

Like all responsible citizens we have been in social distancing since March and throughout this time both my wife and I have been concerned about our house in France.

As infection rates seemed to be easing we decided to make a quick visit to the Dordogne to check all was well. Normally we take a ferry crossing but we really did not want to risk the exposure this would entail. Instead we opted to take the Channel Tunnel. For those not familiar with this route, you drive to the terminal, check in and then get loaded in your car onto a rail transport shuttle train. The journey through the Tunnel takes around 40 minutes and you off load near Calais in France and head south. This route offered minimal exposure to others as we were effectively in the car from door to door and not allowed to leave the vehicle on the shuttle train.

We live in the mid south of England so there was the discomfort of a 2 hour journey to the Folkestone to board the shuttle. Normally we have a 1 hour run to Portsmouth for the ferry. Once in France at Calais there was a 9+ hour run via Paris (not fun) down to the Dordogne. It was tiring but with the two of us taking shifts it eased the strain.

All was good at the house and we spent two weeks with minimal human contact and survived on the French ‘click and collect’ food supply services. We had some very high daily temperatures and some nice wine.

We have a very close friend called John living in France and he knows our house well and envies our Dark Sky location. He has similar interests in Fusion 360, horology, Arduino, mechanical design and relevant to this instance, astro-photography. August is the peak time for the Perseid meteor shower. We both own Canon Powershot SX50 HS zoom cameras and he made a comment that it was a shame that these did not have a Bulb setting for the shutter or the ability for us to do time lapse to take some shots of the meteor trails.

Investigating on the internet revealed that there is a group of enthusiasts that have hacked the operating system of the Canon range of cameras. This is known as CHDK (Canon Hack Development Kit). It allows you to load a firmware update into the camera to expand its capabilities but does not overwrite the default issued code. The CHDK code is wiped once you switch off and the camera reverts to normal.

CHDK provides facilities for long exposure times and for time lapse routines. This therefore addressed both the issues we had with the SX50. It took a while for us to share notes and to get our heads around how CHDK worked and how to set it up. I managed to get my camera hacked the day before it was time to journey home. I had one last night of hopefully cloud free viewing to get some images.

Those familiar with all things astro will know that a long exposure time image of the sky will be degraded by the movement of the Earth’s rotation. The result is ‘trails’ on the stars so they look elongated rather than single dots. John is developing an Arduino based star tracker but I did not have access to this but I did have my Celestron telescope. When the telescope is calibrated and locked it will keep track of the star movement and not leave trails.

I spent the day devising a mount for the Canon on the telescope and come 10 pm all was ready to run … except the cloud cover was really bad. I waited and waited and finally I got one run of 4 shots of 3 minutes each looking at the Milky Way. Given more time these could have been stacked in Registax or similar to enhance the images further.

Milky Way image taken with a Canon HS50 hacked with CHDK to give 3 minute exposures

I accept that the SX50 is far from ideal as an astro imaging camera. There is too much glass in the light path and the filtering and noise will be poor but this was a first step along the road. I was pretty pleased with the result. I now need to compare notes with John on his Arduino based star tracker. Another project to add to the ever increasing list …..

Next day we made the house secure and departed knowing that we now faced not just a 13 hour journey but also a 14 day quarantine period when we got home. But of course the upside is 14 days of uninterrupted workshop time.

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