Parts list for feedback

wall e

Well-Known Member
Man this is making me rethink my 2x72 build list. Avcounting dept still wont bite on the 650 figure but 200 for motor and pulleys is possible. Again I love this forum and all the sets of eyes and ears to help us beginners and advanced builders alike
 

KenH

Well-Known Member
Walt - for $250 shipped or so you can have motor and VFD. Of course, you'll need to protect the VFD with an enclosure, mount VFD away from grinding area, or use filters to protect VFD from the metal grinding dust.

Use skateboard wheels for platen, purchase the drive wheel and tension wheel, buy aluminum cut to length..... you'll still have less than $600 or so in a direct drive 2X72 grinder with VFD control total cost. The only tools you need to build with are a drill press and a metal cutting saw..... Wait, I forgot the 56C motor mount. That would need a lathe for that single piece. I expect that wouldn't be "too" expensive to have that one bit of work done at machine shop, unless you know somebody with lathe.

Ken H>
 
Last edited:

Self Made Knives

Well-Known Member
may as well keep going with this. here is basic wheel set, 4"drive,3"idle,2ea 2"contact($120 delivered) http://www.ebay.com/itm/Belt-Grinde...208?pt=LH_DefaultDomain_0&hash=item3aa2c15078
i would source 1 1/2" square tube or square stock and aluminum plate local as shipping costs as much as the material. you can get a 240vac VFD for the same price as the 110vac one, just need to have access to either dryer or range outlet.
eBay is where I got my wheel set, don't think it was this guy, but there are 3 or 4 guys on there making these wheel sets for about the same price. Actually, I built grinder off of Wayne's Moe's Grinder plans and I only needed one 2" wheel. I emailed the guy on ebay and he priced me a set a little cheaper without the extra 2" wheel. I got my 10" contact wheel from Grizzly for like $80, maybe $90 can't remember for sure. Only thing with the Grizzly wheel, I had to put on a lathe and machine bearing pockets in it.
 

craigbladeworks

Well-Known Member
I'm going to pull the trigger today on polar bear forges GIB. Yes I can probably do a NWG myself for less but I feel like my time to source the materials locally and fabricate would exceed the cost of buying from Jamie.

I will go through eBay for my wheel set. That seems like a great price. Instead of a large contact wheel I'm going to get a small wheel holder and a set of wheels. So those will most likely be ordered by the end of the day.

I'm still undecided on the motor and VFD. I like the options everyone has listed. Just not sure which one yet.
 

craigbladeworks

Well-Known Member
Importance of motor speed? 1725 or 3450? If I get 1725 would a larger drive wheel be necessary to maximize the potential sfpm?

Inverter duty vs general duty vs continuous duty?
 

KenH

Well-Known Member
Well, it depends on which you want, and how much money you're prepared to spend. I went with 3450 RPM motor due to cost restraints. Either one will work just fine.

The 1725 RPM will require a larger drive wheel, OR - pushing the motor to 100% overspeed to get required SFPM. One thing about 1725, you can do the 100% overspeed and still only be at 3450 RPM. "IF" I had both sitting there at same price - I'd go with 1725 RPM motor with maybe a 5" drive wheel.

Ken
 

craigbladeworks

Well-Known Member
Well, it depends on which you want, and how much money you're prepared to spend. I went with 3450 RPM motor due to cost restraints. Either one will work just fine.

The 1725 RPM will require a larger drive wheel, OR - pushing the motor to 100% overspeed to get required SFPM. One thing about 1725, you can do the 100% overspeed and still only be at 3450 RPM. "IF" I had both sitting there at same price - I'd go with 1725 RPM motor with maybe a 5" drive wheel.

Ken
I can across a 1725 1.5hp 3ph for half the motor I was looking at. With a 2year warranty too. But not sure what the overall benefit is of the lower rpm?
 

Self Made Knives

Well-Known Member
If you're using a VFD, you want the 1725 motor. You will still be able to go from 0 to 3600 rpm with that motor, this is the right motor. There's no reason in the world you would ever go faster than that. All the VFD's I've used over the years will run the motor at twice it's rated speed. The motor doesn't care. Don't by a 3600 rpm motor if you're using a VFD!
 

Justin Presson

Well-Known Member
I have been wanting to upgrade to a vfd and have wondered about going with a 1 hp motor to save some money on the vfd, but everyone seems to tell you, you can't make knives with less hp you will stall it. I must be doing something wrong because I can't imagine stalling my 1.5hp now and I rarely stalled out my 1x42 with a .5hp motor on it.
I don't know just food for though especially since I do it part time.
 

craigbladeworks

Well-Known Member
If you're using a VFD, you want the 1725 motor. You will still be able to go from 0 to 3600 rpm with that motor, this is the right motor. There's no reason in the world you would ever go faster than that. All the VFD's I've used over the years will run the motor at twice it's rated speed. The motor doesn't care. Don't by a 3600 rpm motor if you're using a VFD!
What's the reasoning for choosing a 1725 over a 3450? I don't doubt your right just wasn't sure what the reasoning is
 

KenH

Well-Known Member
The idea of using the 1725 rpm motor is the vfd will run up to 120hz. At 60 hz, (line freq) the motor will run at name tag RPM, say 1725 rpm. By overspeeding the motor to 120 hz you 1725 motor will be spinning at 3450 RPM. The advantage of using the 1725 rpm motor, the torque at 60 hz is at a max say at 1800 SFPM belt speed. A 3450 rpm motor running at 50% hz speed 1800 SFPM will be at reduced torque. Of course, at slower belt speeds a lot of torque is not normally required while max torque is more desired at full belt speed of 4000 SFPM - boy you can throw some sparks there.

Got to go - more later unless someone else chimes in to finish.

Ken H>
 

craigbladeworks

Well-Known Member
The idea of using the 1725 rpm motor is the vfd will run up to 120hz. At 60 hz, (line freq) the motor will run at name tag RPM, say 1725 rpm. By overspeeding the motor to 120 hz you 1725 motor will be spinning at 3450 RPM. The advantage of using the 1725 rpm motor, the torque at 60 hz is at a max say at 1800 SFPM belt speed. A 3450 rpm motor running at 50% hz speed 1800 SFPM will be at reduced torque. Of course, at slower belt speeds a lot of torque is not normally required while max torque is more desired at full belt speed of 4000 SFPM - boy you can throw some sparks there.

Got to go - more later unless someone else chimes in to finish.

Ken H>
So I'd be looking at greater low speed torque? That sounds great.
 

KenH

Well-Known Member
I'm now back - had to take wife out to dinner tonight.... small price to pay for clean socks.

Yes, the 1725 rpm motor will give more low speed torque than would a 3450 rpm motor. Remember, for 1800 SFPM (with 4" drive wheel) belt speed, the 1725 rpm motor will be running about 100%, while a 3450 rpm motor would be only 50%, and torque will be similar. BUT - here is the real kicker, at that low speed, you really don't need much torque. You need the torque at high speed where you're doing real hogging of metal. I have a 3450 RPM motor, it was about $50 less expensive than a 1725 rpm motor.

Some folks talk about running at 6,000 SFPM for hogging - hard for me to imagine running that speed. 4K SFPM is pretty fast for me, and that cuts pretty fast.

My thinking (at the time) was the 3450 rpm motor with a 4" drive wheel would give me belt speeds from 4,000 SFPM on high at only a very slight overspeed of motor. At the lower end the 3450 RPM motor will give 800 SFPM belt speed at 25% of motor, and there is still plenty of torque for low speed grinding - a delicate touch is normally used at such low speeds. At times when grinding mammoth ivory I've even slowed down to 500 SFPM speed for "touching" the scale.

When I wish to go hog metal, crank it up to max at 70 hz to give the 4,000 SFPM belt speed.

Again, at same price (maybe even a sight extra) I would go with 1725 rpm.... I think {grinning}

Ken H<>
 

craigbladeworks

Well-Known Member
I'm now back - had to take wife out to dinner tonight.... small price to pay for clean socks.

Yes, the 1725 rpm motor will give more low speed torque than would a 3450 rpm motor. Remember, for 1800 SFPM (with 4" drive wheel) belt speed, the 1725 rpm motor will be running about 100%, while a 3450 rpm motor would be only 50%, and torque will be similar. BUT - here is the real kicker, at that low speed, you really don't need much torque. You need the torque at high speed where you're doing real hogging of metal. I have a 3450 RPM motor, it was about $50 less expensive than a 1725 rpm motor.

Some folks talk about running at 6,000 SFPM for hogging - hard for me to imagine running that speed. 4K SFPM is pretty fast for me, and that cuts pretty fast.

My thinking (at the time) was the 3450 rpm motor with a 4" drive wheel would give me belt speeds from 4,000 SFPM on high at only a very slight overspeed of motor. At the lower end the 3450 RPM motor will give 800 SFPM belt speed at 25% of motor, and there is still plenty of torque for low speed grinding - a delicate touch is normally used at such low speeds. At times when grinding mammoth ivory I've even slowed down to 500 SFPM speed for "touching" the scale.

When I wish to go hog metal, crank it up to max at 70 hz to give the 4,000 SFPM belt speed.

Again, at same price (maybe even a sight extra) I would go with 1725 rpm.... I think {grinning}

Ken H<>
So if I get a 5 inch wheel @ 60hz spinning 1725 I'd be getting 2258 sfm. So I'd have to run my motor at 100% over just to reach 4500 sfm.

Thats my next question what does that mean for the longevity of my motor and would I experience loss of torque? Just trying to get a full picture of everything
 

KenH

Well-Known Member
Yep Craig - you've got the idea. With a 5" drive wheel, at 100% overspeed you'd have 4500 SFPM. With a 3450 RPM motor running at 60 hz, you would have a small amount of extra torque than a 1725 RPM spinning at 3450 RPM. I suspect you'd still have sufficient torque for hogging. Longevity of motor? Well, consider the motor is spinning at the same 3450 RPM (120 Hz) as the 3450 RPM motor is turning at 60 hz. You'll certainly have more torque at 60 hz with the 1725 RPM motor at 2250 SFPM than would the 3450 RPM motor running at 30 hz (50%). BUT - remember, normally at 2200 SFPM you're not hogging to need a lot of torque.

Also, consider what percentage of time the motor will be running at max speed of 200% for 4500 SFPM vs the use at lower speeds.

I suspect either motor will last a LONG time. As I said, I opted for 3450 based solely on cost of $127 shipped vs $166 shipped for 1725 RPM TEFC 2 hp motor.

Ken H>
 

Self Made Knives

Well-Known Member
I've seen those youtube videos of guys running a crazy fast belt speed throwing 4 foot showers of sparks everywhere. Looks impressive for a video, but knife making is more about finesse, IMO. Of course I'm still a new knife maker, but Ican't imagine needing that kind of speed or torque making knives. You put a 36 grit belt on a 1725 rpm 1hp motor only running at 1725 and you are removing plenty of metal. I rarely/never feel the need to go above 2400 rpm on mine. If you look at combo vfd/motor setups, they come with the 1725 motor. I don't think you need to get too wrapped up in how much torque at what speed. You'll never notice the loss of torque over the 1725 motor rating.
 

craigbladeworks

Well-Known Member
Quick update.

I spent the extra cash and got the kbac-27d for my VFD. The motor is a 1.5hp hallmark industries. Both of which I've received. I got my wheels from a company called pfunder fab. Received those as well. Got my GIB in and went and bought the necessary hardware for assembly. I just ordered my gas spring and a couple taps that I needed. Hoping to get assembled this weekend.

Missing a platen though :/ not sure what to order honestly. I was perusing Beaumont metal works site and they sell a platen assembly with bracket and platen but not sure if the standard platen from polar bear forge will have the sane bolt pattern.

Also a little iffy on wiring the VFD and motor.
 
Top