Clever Ideas?

Empire_2

A shaft sleeve would be the easiest way out. As long as you have about 8-10" on each side of the failed bearing this may make your life easier. As far as torque, I have seen quite a few on 15HP blower set ups before and the seem to work great.

Mike T.

Darrell

I've got a large F/A unit in a Mall...the 1-7/16 shaft is eight feet long with two cages on it supported by two midshaft bearings, one trailing end bearing and one driven end bearing. No maintenance and the driven bearing failed cutting the shaft beyond salvage. The unit is up in a scuttle with about three feet on either end of the shaft to work in. Obviously, I'm gonna have to take it out through one wall or the other but it's been in there about 25 years...any clever ideas about how to break it loose and drift it out? The last one I did like this we drilled the shaft end and put in a screw eye so we could put traction on the shaft with a come-a-long! I work alone...my 15 year old daughter is a good hand...but maybe I should pass this one on to somebody else. Oh yeah..the inside of the unit is completely covered in old grease and dust.

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Unknown

Is there,,,

any way you can move the shaft a few inches either direction just to get a good piece where the bearing wants to go? I've done that a few times. As long as the shaft isn't gouged TOO deep it should be ok. As for breaking the fans loose. Pull the setscrews, soak it all with penetrant (the longer the better) then find a way to hold the shaft while you spin the cages. That'll usually break them loose. I've used pipe wrenches in the past but only on sections of the shaft that can be damaged without causing other problems. Either way a mill file followed by some emory cloth will smooth out any marks if they are a problem. It's a good idea to polish up the shaft in all locations where you want it to slide that few inches, oil it all up so it all slides real smoooth...

Good luck!

Brad White

The Gordian Knot...

Darrell, mind if I take a broader view?

After 25 years there is a lot of other things that can go wrong on such a unit. If caked with grease as you say there are health issues. Coil impaction -how would that be cleaned? 25 years ago if a unit had insulation it was typically an inch and exposed to the airstream, something we would not do these days. What would the next thing be to go? Coil or heat exchanger? Dampers? Small things you can replace, the big ones, not so much...

I would offer your customer a price to replace the unit with one of modern construction, cleanable and with a VFD for energy savings while you are at it. Maybe it can go on the roof and intercept the ductwork bypassing the unit entirely?

With multiple wheels on a common shaft, I see a sawzall in your future...
Sure, if you can get the old shaft out, getting the new one in will be a greater challenge.

Maybe that is too simplistic but I think it is an option worth evaluating.

Darrell

Yes, a whole new unit would be nice, but I don't see it happening. That would be well outside the scope of my licensing, not to mention my want to, but, I'll mention it to the owner and can certainly make a referral for him if he decides to go that route...and then I can maintain something nice and new...wouldn't that be a novelty! Currently the owner has disconnected all of the drive motors for the dampers and sets them manually every morning when he comes in based on how much heat he thinks they need in a given zone.

I'm gonna have to clean it all up and slide it out, I guess. The smell of Kroil in the morning just gets me going! I'll climb back in there and see if I can drift the shaft a few inches...I didn't have my noodle head attachement with me yesterday so I could see around all the structure and housing. Somebody suggested sleeving the chewed up portion of the shaft and using an oversized bearing. That would be a seriously cool fix in this case if I could trust it. Anybody ever hear of such a thing?

For you designers that check in here...plan for this kind of thing when you draw up the blue prints! Just a few feet of space would make ever so much difference.

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Mark_7

Your other choice to do on a replacement would be to sub the job to a larger contractor. I have done this when we are too busy to do the work ourself. If you know a good commercial contractor in your area give him a call. We all need to work together.

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Unknown

sleeving...

I BELIEVE you'd have to pull the shaft to sleeve it. I've done this for worn journals on rollers. I'd turn the shaft down to a good surface then machine a sleeve whose ID was .003" smaller than the shaft, heat it up cherry red and then slide it on. Once it cooled there was no getting it back off without cutting or peeling it off in a lathe. There may be other methods of sleeving, this is the only one I happen to know.

Unknown

Safety!

I'm not sure how familiar you are with big belt driven stuff like that but for my own peace of mind I want to tell you that those assemblies carry so much weight that even if they are spinning ONLY SLIGHTLY there can be enough inertia to drag a finger right through the pulley. Just because something is spinning slowly doesn't mean it isn't capable of causing injury. I have the tweaked left index finger to prove it.

Unknown

Could you explain the process?

How does this work?

Rich Kontny_4

Options

I am with Brad on this one, I have the same situation at our church, with an air handler with a hot water coil. I donated time and used the band aid approach on the classroom fan coil units and they nickeled and dimed us to death. After 37 years I told them to replace them. They bit the bullet and do not regret it.

We still have a large air handler w/coil in the gym and it has been there for 40 years now,has one foot of clearance on each side and will be replaced when the shaft, bearings or coil gives us trouble.All mechanical equipment reaches it's life cycle sooner or later!

You need to give a worse case scenario price including wall repair and possible coil damamge if you just replace the shaft. You also can only warranty the replacement not the entire unit. However if they have additional problems after the shaft replacement you are going to be questioned about all future problems. Owners tend own you after you have done service work.

Even if you don't have the license to replace this unit, you will be better off passing up on the repair and suggesting they replace this entire unit. This will make you look extremely honest and acting in the best interest of the owner. You may lose this particular job but you have a chance to gain many points with the owner.

The new unit will come with a fresh warranty and you won't get beat up by a repair gone bad!

Act in the best interest of the owner and you will get a return in future work.

Rich K.

Empire_2

Yes Replace is the best option, BUT

To answer your question, The sleeve type couplings are made of a very hard rubber material backed by a metal , round backing which supports the coupling. The sprocket like appearance interlocks with a mate and allows the shaft to be reconnected or joined to drive as usual. You will need space to do this, but only you can see if you have enough or not. Let me find a web site so you can look at it.... Look at motionindustries.com to take a look. You would use 2 S-Flange's and 1- Sleeve insert....The one on the right is what we use....

Mike T.

Unknown

Thank you!

I call that a "flexible coupling", now I see what you're up to. I had a whole different thing in mind which was just a metal sleeve as I've described above that slides over and then somehow locks onto the shaft. I was thinking it should bey keyed but cutting a keyway in the shaft would be tricky. THEN I remembered you can just grind a flat on the shaftand that will act as a keyway.

I agree replacement is the best option but sometimes getting that to happen is near impossible. Whenever I try to salvage an old piece 'o crap for someone I ALWAYS make sure they understand the realizations of trying to bandaid an old unit and it ain't my fault it's old. There ARE no warrantees other than my work alone and I certainly don't own it once I've touched it. As far as I'm concerned, if he's got so much as 6 extra inches sticking out on either end of that shaft he SHOULD be able to move it enough to put a good surface where he needs it. I can't say it will be easy.

Unknown

I was thinking,,,

I hope the blades aren't keyed to the shaft. If they are and the keys want to be stubborn to get out or can't be reached it could all turn into a big can of worms very quickly. I'd look it all over very carefully before I picked up a wrench. If they are keyed, is the keyway long enought to allow you to shift the shaft over a few inches? If not, can you get a grinder in there to grind that flat I was talking about? How easy is it tto access the other bearing? Is there a bearing between the blades you don't know about yet? Stuff like that.

Brad White

Not Cherry Red...

No doubt that a thermal fit is nearly impossible to loosen at normal operating temperatures.

I respectfully suggest that the shaft not be heated to cherry red which is beyond it's first critical temperature. To do so without proper quenching -impractical I would say- will anneal (soften) the steel and give it a place for torsion shear.

Wayne_16

sleeve the shaft

> How does this work?

Wayne_16

sleeve the shaft

Last year I worked with a service tech that had the same problem. Long shaft, worn at the bearing, age, no room etc.

The solution was to sleeve the shaft where the bearing rides. His sleeve was approximately 8" long, machined to fit the shaft snug, then welded in place by a certified welder. the outside shaft diameter was determined by the replacement bearing. In this case the mounting bracket had to be changed to accomadate the new bearing. The shaft was never moved and the opposed bearing is still in place.

While working on the project, I thought of the dead men that once installed the blower assemby. The fan wheel was approximately 7' wide and over 8' tall.

Good luck, Wayne

Darrell

I have a plan!

D2, (my second daughter, 15 and a good hand), and I climbed inside the beast and looked it over. The first order of business will be to install some industrial weight rubber floor mats over the fiberglass, and then clean up the grease boogers flung all over the inside of the box. There is a mid-shaft horizontal pillow block bearing. Both cages are fixed on flats with set screws instead of keyways. The trailing bearing is also a horizontal pillow block bearing. The driven bearing, the one that failed, is a vertical pillow block mounted through the sheetmetal box, (poor design...too much flex), and destroyed 1-1/2 inches of shaft. The driven shiv is keyed, and the keyway is quite long. I have exactly 2-1/2 inches of tail shaft, and I need to drift the shaft 2-1/4 inches. On paper all the right spots will line up just right. I will open up the box on the trailing end and use a hydraulic bottle jack for force.

We talked with the owner...He is trying to sell the mall and replacement equipment is included in the deal...but, he would really like for me to make the existing equipment work for the near term. He is a general contractor and fully understands that I may not be succesful...he offered to advance my labor in good faith. I have worked for him alot over the last twenty years, and have an agreement from him for PHVAC maintenance in the mall and his other various properties.

And, yes, I've run my pinky through several shivs...you'd think once would be enough!

Just for my information, how come nobody puts idler wheels on these units with long belts? This once has a pair of 81 inch belts, and the belt whip is transmitted to the whole unit. Looks to me like an idler would save alot of wear and tear.

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Unknown

Good LUCK!

I was thinking a pneumatic hammer might help move it along if you have trouble otherwise.

I'm, always impressed with a kid that can hold their own. Your 15 yo is cool BUT I watched an 8 yo boy run a bobcat like an old pro a couple weekends ago. He was like a tiny little man. LOL...

I mentioned the safety becasue my Chinese resturant owner friend ran HIS pinky though the pulley on his exhaust fan. The motor pulley was loose on the shaft and it was causing the blower to hang up on start up. His solution? Grab the belts and give it a push. When it finally got him it took off the finger up to the first joint.

zeke

He's heating the sleeve, not the shaft.

Unknown

Right,,,

In my case we were reparing end shafts (or journals) on big rollers for a sheetmetal web. They were special in the way that the entire roller was submerged in caustic solution so any kind of roller bearing was out. We used a plastic compound for friction bearings and stainless journals on the rollers. The bearing and journal would wear simultaneously so we'd put about a 1/2 sleeve on the journals and machine a bearing to fit. When too much slack developed we'd skin the journal sleeve off to true it up(if there was enough meat left) and machine another bearing to fit. Once the sleeve got close to being worn through we'd cut it lengthwise with a die grinder, peel it off and start all over again. The real trick was dialing it all in to a couple thousandths on a nine foot lathe. I put the rollers in with a crane.

What I loved was I would build this little "oven" out of fire bricks and use a big rosebud to heat the sleeve in there. When it was nearly white hot I'd pick it up with a big pair of channel locks and slide it right on the journal. Once it cooled, it wasn't going anywhere.