BlueTR3A-5EKT Posted October 11, 2023 Report Share Posted October 11, 2023 (edited) 5 minutes ago, Charlie D said: I got the last message off as soon as I saw what you had put, hoping to reach you before you did it. I shall now eleborate a bit more. I once tried a PWM controller on an AC motor and it did not work properly. The speed of the sort of AC motor you probably have is controlled, as Bob said, by the frequency of the AC. I did get some speed change with the AC motor but there was no power with it and the motor stalled easily (and got hot.) Thank you for that. I shall not attempt it, I did worry that the starting current might exceed the controller’s power rating. It is Chinese made, so what is described on the data plate could be fiction. I will keep it for lowering the temperature of our wok and my soldering iron when it is used to solder white metal models. Edited October 11, 2023 by BlueTR3A-5EKT Quote Link to post Share on other sites
RobH Posted October 11, 2023 Report Share Posted October 11, 2023 (edited) The simple SCR controller works by cutting off the waveform either partway through the cycle or in bursts of cycles. That is fine for heating elements but ordinary induction motors don't like it much. The speed of an induction motor does not depend so much on the voltage of the supply but rather on the supply frequency and on the number of poles in the motor. It wants to rotate in step with the supply frequency - known as synchronous running. Although the mean voltage is reduced by this controller, so is the power so that even if it runs, the motor torque is low and speed will depend on the motor load. When speed is reduced this way the 'slip' (the difference between actual motor speed and synchronous speed) is large, and so current draw will be high - hence the overheating. The right way to do it, as Bob says, is with a variable- frequency inverter drive which will not reduce the motor torque. Edited October 11, 2023 by RobH Quote Link to post Share on other sites
BlueTR3A-5EKT Posted October 11, 2023 Report Share Posted October 11, 2023 (edited) 55 minutes ago, RobH said: The simple SCR controller works by cutting off the waveform either partway through the cycle or in bursts of cycles. That is fine for heating elements but ordinary induction motors don't like it much. The speed of an induction motor does not depend so much on the voltage of the supply but rather on the supply frequency and on the number of poles in the motor. It wants to rotate in step with the supply frequency - known as synchronous running. Although the mean voltage is reduced by this controller, so is the power so that even if it runs, the motor torque is low and speed will depend on the motor load. When speed is reduced this way the 'slip' (the difference between actual motor speed and synchronous speed) is large, and so current draw will be high - hence the overheating. The right way to do it, as Bob says, is with a variable- frequency inverter drive which will not reduce the motor torque. Thank you my research has found this article I am able to read it….. https://lancesworkbench.conryclan.com/2021/04/adding-variable-speed-control-to-my-lathe/ I have seen adverts from Newton Tesla for kits to convert the lathe/mill etc. https://www.newton-tesla.co.uk/product-category/lathe-speed-controls/inverter-motor-packages/ Edited October 11, 2023 by BlueTR3A-5EKT Quote Link to post Share on other sites
RobH Posted October 11, 2023 Report Share Posted October 11, 2023 (edited) 25 minutes ago, BlueTR3A-5EKT said: my research has found this article Yes - that is more on less what I have on my lathe. Easy to swap the motor for a 3-phase one if it is separate, as it is on my ancient flat-bed Drummond. If the motor is built-in and single-phase you would have to use a compatible single-phase output inverter like this. https://www.ebay.co.uk/itm/202961268563?hash=item2f416f2f53:g:bgEAAOSwB1Nfzu4R&amdata=enc%3AAQAIAAAA0FrIQUaQOU2%2FW0qCFxInxtATf5X3KtvVEl3FGOXX3zCPqWKCkECM4jd%2FsrNbhuB0p7RP2IUqamDllb7bAnLSblZGzCMl%2BTNulvKdsdYTK2J9L3ZgRPK05%2BKLmPRA%2BA%2BNiXM4ab2vvUHdfBVzTCSRU35jPiMYREAYJtNNb8yeiVgtLz%2FBx%2BLmYBiNKzHYUVoI8ypwO8scja7OsUpHxPvASpiNYmcbJUA%2B6sGuNSSVkZitcMQnJnl67o9I3ZGyARLKvbK4o%2BNxnCn4eKEmZ%2B2SFpw%3D|tkp%3ABk9SR4SE6O_jYg If you are looking at inverters don't confuse the input description (single phase ) and the output (single-phase or 3 -phase to match the motor). Sometimes the sellers descriptions are a bit confusing. Oddly, single-phase to 3-phase ones seem to be cheaper. Edited October 11, 2023 by RobH Quote Link to post Share on other sites
RobH Posted October 11, 2023 Report Share Posted October 11, 2023 The Newton-Tesla kits are good but a bit expensive. I bought an inverter and a new 1/2HP 3-phase motor for under £200 total, though of course I had to make up my own control box and wire the system. Quote Link to post Share on other sites
Charlie D Posted October 11, 2023 Report Share Posted October 11, 2023 I've noticed that second hand three phase motors seem to go for reasonable prices on eBay. I guess that there is less demand for them than single phase motors. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted October 11, 2023 Report Share Posted October 11, 2023 (edited) 2 hours ago, RobH said: Yes - that is more on less what I have on my lathe. Easy to swap the motor for a 3-phase one if it is separate, as it is on my ancient flat-bed Drummond. If the motor is built-in and single-phase you would have to use a compatible single-phase output inverter like this. https://www.ebay.co.uk/itm/202961268563?hash=item2f416f2f53:g:bgEAAOSwB1Nfzu4R&amdata=enc%3AAQAIAAAA0FrIQUaQOU2%2FW0qCFxInxtATf5X3KtvVEl3FGOXX3zCPqWKCkECM4jd%2FsrNbhuB0p7RP2IUqamDllb7bAnLSblZGzCMl%2BTNulvKdsdYTK2J9L3ZgRPK05%2BKLmPRA%2BA%2BNiXM4ab2vvUHdfBVzTCSRU35jPiMYREAYJtNNb8yeiVgtLz%2FBx%2BLmYBiNKzHYUVoI8ypwO8scja7OsUpHxPvASpiNYmcbJUA%2B6sGuNSSVkZitcMQnJnl67o9I3ZGyARLKvbK4o%2BNxnCn4eKEmZ%2B2SFpw%3D|tkp%3ABk9SR4SE6O_jYg If you are looking at inverters don't confuse the input description (single phase ) and the output (single-phase or 3 -phase to match the motor). Sometimes the sellers descriptions are a bit confusing. Oddly, single-phase to 3-phase ones seem to be cheaper. Which Drummond? We grew up with our father’s flat belt driven one that also had provision for treadle drive My brother has now sold that and got a v belt drive one which must be 50 years newer. http://www.lathes.co.uk/drummond/index.html Edited October 11, 2023 by BlueTR3A-5EKT Quote Link to post Share on other sites
RobH Posted October 11, 2023 Report Share Posted October 11, 2023 (edited) Yep that's the one - Drummond M, though mine is slightly later than that one I think, 1934, so has some minor 'refinements' ( plus some alterations over the last 89 years). That was the basis for the later Myford 7 I understand, and some of the Myford bits fit, though sadly not the leadscrew which on mine is now very worn. I think mine has an early Myford cross-slide. Edited October 11, 2023 by RobH Quote Link to post Share on other sites
BlueTR3A-5EKT Posted October 19, 2023 Report Share Posted October 19, 2023 (edited) This weeks game. To recreate the mad Marx real oil seal housing from the drawings Lebro posted. Started with an 1” of cds tube. From M Machine Metals http://www.m-machine-metals.co.uk/ The carriage equalled the metal cost. light internal skim to get a register. Face ends. Mount on my good 3 jaw chuck that is within a couple of thou concentric. Bore to a accept the alloy seal housing. Drill and tap some 5/16” square bar to M6 Get brother to weld the square bits to the periphery in the right locations. Face and test concentricity. Turn the seal housing to drawing. Relieve the oil spill hole to 5 mm with mill bit 8 mm deep. Deburr and away we go. Edited December 4, 2023 by BlueTR3A-5EKT Quote Link to post Share on other sites
RogerH Posted October 19, 2023 Report Share Posted October 19, 2023 This weeks game. To recreate the mad Marx real oil seal housing from the drawings Lebro posted. Started with an 1” of cds tube. From M Machine Metals http://www.m-machine-metals.co.uk/ Hi Pete, what was the 1" tube used for ??? Roger Quote Link to post Share on other sites
BlueTR3A-5EKT Posted October 19, 2023 Report Share Posted October 19, 2023 (edited) 7 minutes ago, RogerH said: This weeks game. To recreate the mad Marx real oil seal housing from the drawings Lebro posted. Started with an 1” of cds tube. From M Machine Metals http://www.m-machine-metals.co.uk/ Hi Pete, what was the 1" tube used for ??? Roger An inch length of 115mm od x 95 mm id. Stupid boy. Edited October 19, 2023 by BlueTR3A-5EKT Quote Link to post Share on other sites
Lebro Posted October 19, 2023 Report Share Posted October 19, 2023 That's a lot more TRouble than I went to ! Bob Quote Link to post Share on other sites
BlueTR3A-5EKT Posted October 19, 2023 Report Share Posted October 19, 2023 11 minutes ago, Lebro said: That's a lot more TRouble than I went to ! Bob You have a Chuck with deep enough jaws to grip the original alloy seal. Quote Link to post Share on other sites
Lebro Posted October 20, 2023 Report Share Posted October 20, 2023 Click on to enlarge. Found these photos just now on how I machined the scroll seal housing Bob Quote Link to post Share on other sites
BlueTR3A-5EKT Posted October 21, 2023 Report Share Posted October 21, 2023 10 hours ago, Lebro said: Click on to enlarge. Found these photos just now on how I machined the scroll seal housing Bob I have 4 jaw chuck envy. Mine is a 3” Burnard item Quote Link to post Share on other sites
Z320 Posted October 21, 2023 Report Share Posted October 21, 2023 +1 you found a suitable lip seal and cut it with a sharp knife yourself? Ciao, Marco Quote Link to post Share on other sites
Lebro Posted October 21, 2023 Report Share Posted October 21, 2023 Yes, I had forgotten that I had used the hose clip to clamp it together, & that I had used my 4 jaw chuck. Bob Quote Link to post Share on other sites
BlueTR3A-5EKT Posted October 21, 2023 Report Share Posted October 21, 2023 2 hours ago, Z320 said: +1 you found a suitable lip seal and cut it with a sharp knife yourself? Ciao, Marco It is an available spare part from Bastuck We can buy in UK from TR shop. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted October 21, 2023 Report Share Posted October 21, 2023 2 hours ago, Lebro said: Yes, I had forgotten that I had used the hose clip to clamp it together, & that I had used my 4 jaw chuck. Bob I tried that but my dinky little 4 jaw would not go big enough safely. I tried the hose clamp around the housing trick you used and attempted to grip it internally on fibre pads. That way the boring tool struck the tip of the inner unused jaws step. Have subsequently found my brother has a 6” 4 jaw for his Drummond Myford Now, All I would need to do to use it is make a nose spindle adapter plate to fit that chuck with the Boxford 1 1/2” diameter thread. Challenge with big 4 jaw or any large chuck is the clearance over the bed when the jaws are opened out. The Boxford having only 4 1/2” bed clearance ( 9” swing) at the headstock is an issue, it is course even less over the cross slide.. Not so on the Drummond Myford with its gap bed. You can get a flock of sheep under the chuck at the headstock on that, even though the bed clearance is 3 1/2” over the ways. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 2, 2023 Report Share Posted November 2, 2023 (edited) Brother came over today and we set about making overider stays for the front of a TR3A in stainless steel. The stainless steel tube per metre cost more than a pair of finished chrome stays…. We managed to flatten one tube incorrectly, but that is all part of getting near lunch. Here we go. We need to get the bolts sorted and do some minor blacksmith type hammer work to get the things to fit. Polishing will be after the welding. Certainly still cheaper than re chroming an original pair. First pic is the desired item. Edited November 2, 2023 by BlueTR3A-5EKT Quote Link to post Share on other sites
RogerH Posted November 2, 2023 Report Share Posted November 2, 2023 That looks like fun Roger Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 2, 2023 Report Share Posted November 2, 2023 26 minutes ago, RogerH said: That looks like fun Roger A boy’s day in the shed with a greasy breakfast lunch to fill in at half time. Quote Link to post Share on other sites
Z320 Posted November 2, 2023 Report Share Posted November 2, 2023 Good result! Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 2, 2023 Report Share Posted November 2, 2023 43 minutes ago, Z320 said: Good result! We Shall not be giving up our day jobs to become overider stay barons Quote Link to post Share on other sites
Lebro Posted November 2, 2023 Report Share Posted November 2, 2023 What better way to spend a rainy day. Bob Quote Link to post Share on other sites
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