MemberOctober 9, 2020 at 1:24 pm
Howdy everyone, wanted to share a story and ask a question.
I have 3 KGL-100's in the kitchen I service and one of them was apparently not working and making “odd” sounds, so I took a look at it and it sounded like the combustion blower was turning on but having problems, so I pulled it and the wheel split apart and was grinding, so yeah, it was making odd noises.
It also ground through part of the case but we were able to fix that with some JB weld, looks good as new.
Then came the point of trying to get a new wheel, of course, I have to buy the entire fan assembly for almost $1K so I had the idea of trying to 3D print it, and lo and behold, it was the right size to fit on my printer so I drew it and then printed it.
Then I realized at some point that the fins were pointing the wrong way so I tried it anyways to see if it would work, it would light, but it was unstable and would die out pretty fast, so I flipped the fins back around and reprinted it.
I then measured the air speed leaving the blower just for curiosity, the fan wheel with the wrong fins was pushing air out at 18 MPH, the one with the correct orientation was pushing it out at 32.6 MPH.
Wow! what a difference that made.
I'm now going to install it and re-test but I thought it was cool so I wanted to share it with you guys.
Now the question I had was, what do you think happened to the wheel for it to split like that?
MemberOctober 9, 2020 at 2:59 pm
With my experience on my Hobart dishwasher, it could be as simple as the fan wheel is made of cheap metal and due to the humidity or moisture in the air caused it to rust and deform the fan blades, and the stress of the air resistance caused it to fail.
MemberOctober 9, 2020 at 3:52 pm
Yeah, that was my original assesment, but I wanted to ask around, see if there was any other cases.
This one is actually plastic, not even metal.
MemberOctober 9, 2020 at 5:43 pm
Ok, you say the wheel is made of plastic. Right? What is it's diameter and width?
Now being a combustion blower, It has a very specific volume and pressure curve to have the right fuel air mix. The question here is what degraded the wheel to the point of failure. Commonly with plastics, it's UV, heat, and a chemical incompatibility. How fat away from the burner? Direct UV from the flame? Heat saturation from the location? Any chemical exposure to the wheel? Like cleaners that are chlorinated or solvents?
MemberOctober 9, 2020 at 5:49 pm
Diameter if I remember is around 140MM at the center of it's circle, width is around 50MM if I Rememebr correctly.
It's not in direct contact with the flame or close to it, it does get hot where it is, so I think that didn't help either. Also, no UV, might be some limited amount of chemical but not much since it's enclosed in the unit.
I measured the output of this VS the output of the original, the original does 2.5 MPH flow at the outlet of the flue, mine does 3.0 MPH, which I think is just due to mine not having any dust on it to cause drag.
Burner lights just fine, flame looks good and stable and it stays lit till it turns off, so it seems to have worked.
Only thing I don't like is the vibration, my wheel is not nearly as balanced as it could be.
Single phase motor.
MemberOctober 9, 2020 at 5:44 pm
I forgot to ask, Is the motor single or 3 phase?
MemberOctober 9, 2020 at 8:46 pm
Vibration will kill a blower wheel. Especially metal ones. Is the motor a split phase? Wrong capacitor will make a vibration. But I suspect the printed wheel isn't balanced. You original may have gone out of balance from foreign material.
MemberOctober 10, 2020 at 8:41 am
Yeah, I figured it would, the original wheel is plastic though, so I suspect it has some give, the RPM's are 3400 so it's pretty quick for a little wheel like that.
I agree with you, I found no other signs of anything having gone amiss so it must've just been something inherent to that particular fan wheel.
I'll have to figure out how to make a balanced wheel though.
MemberOctober 10, 2020 at 12:28 pm
A crude way is to spin at high speed and use a marker to hit the high spot. Check the old one for the metal spring clip they used to balance it. Coarse that's the fin that usually fails first. By where you place it in relation to the hub side, you increase or decrease it's effect.
The problem with plastic ones is that they never maintain the same shape over time. Gravity and heat allow warpage and then the out of balance increases it. Fan plastic is normally quite a ridgid composite material with Nylon or deltrine and often fibers like fiberglass or graphite.
I once had to work with a pale green composite that was stronger than steel. It was near impossible to machine and would take the edge off a mill or drill in nothing flat. You also couldn't grind it as it filled the wheel up.
MemberOctober 10, 2020 at 5:53 pm
Not a bad way to do it, I have a wheel balancer though for this particular purpose, a very simply one, but it works.
That's a good point, I kind of wondered if their wheels would retain it's balance over time, figured between the dust buildup and whatever else happens, it would probably change over time.
MemberOctober 11, 2020 at 6:01 pm
Many years ago I had a strobe tach. For checking real speed. With one of them you could place numbers on the wheel and a static reference with distance measurements. By manipulating the speed knob you could bring up any number to the reference distance point and determine were the run out is.
MemberOctober 12, 2020 at 9:56 am
We had our electronics guy make one of those, put a piece of tape or something on the wheel and you could measure the RPM's of the wheel, added a speed knob to the motor and you could check the various sppeds, it's a very handy tool.
MemberOctober 14, 2020 at 6:29 am
Olivero, I can give you a simple static balance method. First you need a shaft the same diameter as the wheel. Drill rod works best for this as it is straight and polished. Now you need to mount 2 razor blades standing straight up, parallel, and level slightly wider than the wheel. The blades or knife edges as they are called in this application are to minimize friction. Now verify that the shaft is straight by placing one the edges. Rotate to all 4 quarters. Now mount your wheel and place on the edges. The heavy side will immediately go to bottom. You can now add weight to the top till it will stay at a horizontal plane. Best spot on a blower wheel to add weight is 1/4 to 1/3 away from the rigid/hub side.
Oh, don't get cut!
MemberOctober 14, 2020 at 6:41 am
I forgot to tell you a easy way to mount the blades.
Two pieces of 1 by 2 slightly longer than the wheel radius. Saw a groove 1/4 inch deep in the end. This is where you can slid in the razor blades. Mount vertical on a 1 by 6 piece that's slightly longer than the wheel width plus a inch. You now have a simple balancer.
Log in to reply.