Jet or Wivamac
- Thread starter themackay
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paulm
IG paulm_outdoors
I already chose the Wivamac :lol:
Both good machines though.
Cheers, Paul
Both good machines though.
Cheers, Paul
gregmcateer
Established Member
Oh to have the choice!!
bogmonster
Established Member
I think I would have the Jet but both out of my price range so not looked really close at either.
BM
BM
chipmunk
Established Member
For me it'd have to be the Jet for the outboard turning facility and the bed extension that can be lowered to provide increased capacity over the end of the bed.
IMO it's been designed by a serious bowl turner.
I could only afford the 1642 when I last changed my lathe and have tried to mimic the bowl turning feature with the AVSL 1200 outboard rest which is not as good.
HTH
Jon
IMO it's been designed by a serious bowl turner.
I could only afford the 1642 when I last changed my lathe and have tried to mimic the bowl turning feature with the AVSL 1200 outboard rest which is not as good.
HTH
Jon
jpt
Established Member
I looked into this question a while ago because I was changing my lathe and hoping to extend my workshop to accommodate one of these. The conclusion I came to was the Jet is the better lathe on a number of small areas plus one big item which made the decision for me.
Do you intend to move the headstock either to the end of the bed or to swivel it for bowl turning, if so go for the Jet even though the headstock doesnt swivel. To move the headstock on the jet you pull a lever and can then slide it up and down the bed and relock it in any position by just pushing the lever again. The Wivamacs are a different proposition this is a link to a copy of the manual, http://wivamac.com/sites/default/files/ ... k_2008.pdf have a look at the bottom of page 11.
john
Do you intend to move the headstock either to the end of the bed or to swivel it for bowl turning, if so go for the Jet even though the headstock doesnt swivel. To move the headstock on the jet you pull a lever and can then slide it up and down the bed and relock it in any position by just pushing the lever again. The Wivamacs are a different proposition this is a link to a copy of the manual, http://wivamac.com/sites/default/files/ ... k_2008.pdf have a look at the bottom of page 11.
john
paulm
IG paulm_outdoors
The wivamac headstock locking was an occasional minor annoyance for me, but only needed a spanner top and bottom. I superglued the top nut in place inside the headstock and added a hefty bristol lever underneath, works great, just turn the lever and slide the headstock and nip the lever up again. Don't know why the manufacturer didn't do something similar similar but easily resolved if it annoys in use 
The Jet only has two pulley wheels to try and maintain the torque when turning large pieces at low rpm, whereas the wivamac has five, which allows you to keep maximum torque at a range of speeds, especially useful for example when using a coring system which does involve heavy cuts at low speed.
Cheers, Paul
The Jet only has two pulley wheels to try and maintain the torque when turning large pieces at low rpm, whereas the wivamac has five, which allows you to keep maximum torque at a range of speeds, especially useful for example when using a coring system which does involve heavy cuts at low speed.
Cheers, Paul
Hi Paul thanks for information,I am leaning towards the Jet mainly due to the price difference would really like the Wivamac though As you say moving headstock is not an issue especially after your modification ,you would think the manufacturer would fit a lever.I see what you are saying about torque , I would imagine the Jet should handle anything I am liable to do.I will be using a woodcut bowlsaver though which I have not used yet.
bogmonster
Established Member
Not wanting to go too far off topic but the question of torque fall off at low RPM interests me. This is my understanding but I may be completely wrong so please don't shoot me down.
My understanding is that the torque does not fall off appreciably until the RPMs get very low. As the frequency decreases the resistance goes up and the inverter reduces the voltage to maintain an even torque (otherwise the power and torque would go up but also the motor may go up in smoke). The inventor does this usually with pulse width modulation (turns current on and off quickly) to get an approximation of the desired voltage. If anything it is when a motor is run faster than its designed frequency that torque needs to fall off as the voltage would need to increase beyond what was intended for the motor - result equals motor going up in smoke. Instead the voltage is kept the same and the torque decreases.
I think the issue comes at very low RPMs where the variable torque at different points in rotation creates a pulsating effect. At higher RPMs the pulsating effect is not very noticeable. This is why some variable speed systems are not intended to be run at less than a given RPM. E.g. my lathe starts at 50 RPM. Of course a lump of rotating wood acts as a flywheel that helps even out the torque pulses but only up to a point.
So I think if you want to turn at very low speeds < 50 RPM for example then having a low ratio pulley system will help avoid the pulsating. Personally I only run at 50RPM when sanding.
May have all that totally wrong.
Either way I know lots of people use bowl savers on the Jet (or the Powermatic or whatever the American version is, the mustard coloured thing) so I don,t think you will have a problem. In fact I was watching a video demo of the Kelton bowl savers on a Powermatic lathe the other day.
BM
My understanding is that the torque does not fall off appreciably until the RPMs get very low. As the frequency decreases the resistance goes up and the inverter reduces the voltage to maintain an even torque (otherwise the power and torque would go up but also the motor may go up in smoke). The inventor does this usually with pulse width modulation (turns current on and off quickly) to get an approximation of the desired voltage. If anything it is when a motor is run faster than its designed frequency that torque needs to fall off as the voltage would need to increase beyond what was intended for the motor - result equals motor going up in smoke. Instead the voltage is kept the same and the torque decreases.
I think the issue comes at very low RPMs where the variable torque at different points in rotation creates a pulsating effect. At higher RPMs the pulsating effect is not very noticeable. This is why some variable speed systems are not intended to be run at less than a given RPM. E.g. my lathe starts at 50 RPM. Of course a lump of rotating wood acts as a flywheel that helps even out the torque pulses but only up to a point.
So I think if you want to turn at very low speeds < 50 RPM for example then having a low ratio pulley system will help avoid the pulsating. Personally I only run at 50RPM when sanding.
May have all that totally wrong.
Either way I know lots of people use bowl savers on the Jet (or the Powermatic or whatever the American version is, the mustard coloured thing) so I don,t think you will have a problem. In fact I was watching a video demo of the Kelton bowl savers on a Powermatic lathe the other day.
BM
paulm
IG paulm_outdoors
The Jet seems to be a good machine too, and if the price difference is significant then it must be tempting, don't think you'll go far wrong with either
Cheers, Paul
Cheers, Paul
jpt
Established Member
themackay":34odsgxl said:
Unfortunately no, the plans to extend my workshop didn't happen so there wasn't room for it, instead I went for the Axminster AT1628VS which I could mount on my existing bench.
Like the Jet it only has 2 pulleys which was a bit of a worry for me as I turn some big burrs so need the power at slow speeds. I have just finished rough turning a 24" x 10" chestnut burr which I had to start turning at about 185 rpm and the only time I could slow the lathe down was when I tried to take a very deep cut which when I measured it was just under 1". Apart from that it has been perfect.
john
bogmonster
Established Member
Done a bit more reading - my son is interested as he is doing an engineering course. It seams that torque drop off starts at 8% of motor speed for simple v/hz inverters and improves down to 2% for open loop vector inverters and 0% for closed loop vector inverters. No idea what type of inverter is in my 1628VS but I expect an open loop vector (I think these tend to be used more where braking and reverse operations are needed). Taking worse case of a v/hz style it will deliver full torque at about 100 RPM and up on the lower belt setting. If it is the vector type it will deliver full torque at about 27 RPM. In either case I can't see additional belt ratios helping much? With the 6000/diameter rule you would need to be turning greater than a 60" bowl at this speed to start getting torque drop off with a v/hz inverter. Sure, many people start at slower speeds than that so lets say a 3000/diameter giving a 30" bowl.
EDIT: Sorry, I get question in my head and need to dig away at it. The drive is a simple V/hz (V/f) drive but with a torque compensation at start up delivering up to 150% additional torque for 60 seconds. So, the short answer is on the 1628VS under normal running conditions full torque is delivered at about 100 RPM. I suspect that is why the lathe is stated as starting at 50 RPM. Maybe lathes whose variable speed starts at near zero use the vector style inverters?
BM
EDIT: Sorry, I get question in my head and need to dig away at it. The drive is a simple V/hz (V/f) drive but with a torque compensation at start up delivering up to 150% additional torque for 60 seconds. So, the short answer is on the 1628VS under normal running conditions full torque is delivered at about 100 RPM. I suspect that is why the lathe is stated as starting at 50 RPM. Maybe lathes whose variable speed starts at near zero use the vector style inverters?
BM
bogmonster
Established Member
Of course if you want to turn really big things try this:
http://lumberjocks.com/topics/5901 - scroll down a bit....
BM
http://lumberjocks.com/topics/5901 - scroll down a bit....
BM
duncanh
Established Member
Last year I bought a Wivamac 6000. A Jet lathe wasn't even an option in my considerations as I don't have the space to take the headstock to the end and turn large stuff. The rotating head stock on the Wivamac is why I bought it. Having to use a spanner to move the headstock is a very minor inconvenience - it really doesn't take that long.
I also have the rotating extra bed for turning with the head rotated. It's very useful and fold away easily under the main bed when not in use.
I also have the rotating extra bed for turning with the head rotated. It's very useful and fold away easily under the main bed when not in use.
I think the conclusion is they are both excellent lathes ,one with swivelling headstock and one where headstock is slid along to end of bed achieving the same ability to turn very large diameters .I think the weight in the Jet is a plus factor although the Wivamac is said to be stable although it is much lighter.So really comes down to price in the end as either machine will do more than I am likely to ask of it.
duncanh
Established Member
I've remembered one annoyance with the Wivamac - the box with the inverter takes up a lot of space under the lathe where I previously had a waste bin. I guess it could be mounted somewhere else but I've just never got round to it
