BX2750D Snowblower Wormgear repair Help

[Southernfarm]

The bronze ring gear must have been heated to expand then put on the hub and allowed to cool. Looking closely at the alternating dents/grooves on the hub that must have been the way it was made.

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[kupitz]

Messicks price for complete gearbox and shafts is $473 USD and will call dealer tomorrow for local. The may also have just the gears but no longer made.

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That would really tick me off, I paid just under $700 for the gearbox from Messicks in Feb. 2015!

 

[Southernfarm]

In Canada at my dealer, the gearbox is $693. Just the two gears are also available for $592. For that extra $100 you get fully assembled with new shafts and seals. I am going to see about getting a Machinist to make me a gear. Perhaps even a better made one.

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[Southernfarm]

That would really tick me off, I paid just under $700 for the gearbox from Messicks in Feb. 2015!

The $473 I got from Messicks website just yesterday.


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[Southernfarm]

Looked more closely and looks as though the worm gear was not engaging the ring gear in the center but off to one side. The worm gear is also ribbed on the inside to match up with the indents you see on the hub. No markings that I can find to show who made it for Kubota.

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[JeffL]

The hub on the gear looks like it was cast on the shaft and then machined. The gear and shaft were most likely machined together as one unit. This set up is probably beyond most machine shops. A complete redesign on the joint is possible. Then with all that the price from Messics doesn't sound to bad. Jeff

 

[kubotasam]

My thought (and I may be way off base here) is that the bronze gear is cast around the steel center section. then machined.

 

[JeffL]

I really can't tell just from the pictures if the gear was cast or PM. I see traits of both. Determining the actual process used really only satisfies our curiosity. The main point is the gear and shaft is a permanent unit not easily reproduced.

 

[Yooper]

I had been toying with the idea that the bronze gear could have been cast in my home foundry, I have a 15KVA induction furnace that would easily melt bronze and her many alloys.

I would have used a new gear to use as my pattern, RTV compound to make a mold that would have given me a negative impression to make wax positive copies. The positive copy would have been encased in plaster then burned out to be replaced with molten bronze.

This type of casting is called lost wax and you can make some very intricate pieces.

The internal dimples of the gear mating to the external ones on the shaft are giving me a problem getting my head bent around this as I do not think the manufacture would have been able to heat the gear enough to expand it enough to slip over and mate with the external dimples on the hub.

This needs more investigating, probably make a call to the dealers shop guys see if I can get a copy page from the shop manual regarding installation proceedure of the gear.

As I;m sure that bronze gear is also used in many different models of Kubota snow blowers.

Please take pictures and post if you do cast this gear! Would love to see the process!

 

[Tooljunkie]

"spring pin", is that a Kubota/oriential term? I always referred to THEM as a roll pin.

A spring pin is a roll pin,and a split pin.
A roll pin is a couple layers rolled up and a split pin is a single layer with the split.
Roll pin is tougher.
Southernfarm, looks like the weather did improve,now a little too warm. Good thing i brought back the nice weather i had while on vacation on a cruise ship.
In so happy i missed the nasty cold.

Having shaft machined/reworked is fine if making gear is viable. A coarse spline may be enough to lock gear on shaft. My guess shop rates would make this job worth more than replacement gearbox. Unless machinist already has tooling. Building a cutter for hobbing the gear would eat a fair amount of time.

 

[Dave_eng]

Many years ago as a second year engineering student, we studied casting.
What always has to be taken into account are the thermal effects.

You make an exact mold, i.e. one that is the same size as the original part.
Then you fill this mold with molten, i.e. very hot metal. You have designed the mold well and it tolerates the extreme temperatures and has vent holes in the right places to let all gases out and the molten metal fills the mold completely.

Everything cools and you take out the new part.
You measure it against the part used for the mold making and the new part is too small.

The change in dimensions of the part is significant when setting up clearances to parts that are going to mate with it as the case with the worm gear.

In some instances the answer to this problem is to make the mold with a special plaster which expands when it sets. This expansion makes a mold for the molten metal just a little bit bigger than the original part.

Now when filled with molten metal and allow to cool you end up with a part the same size as the original.

This involves a lot of trial and error before you get a perfect piece.

My project was to make a high performance manifold for a weber carb.

When the mold was l done I took it to a foundry to have it cast in an aluminum alloy. Unfortunately for me, the mold did not fill completely and one of the ears for mounting the carb to the engine was half there. It took a lot of work to reach the point of pouring the molten metal in and I ended up with a piece of junk and the mold was destroyed in the casting process.

If I was in your predicament, I would be looking for a more traditional farm tractor style gearbox and work to make the fan and auger work with the gear box. The worm gear style in my experience is more often found on walk behind snow blowers.

Dave M7040

 

[Dave_eng]

From what I can see many larger snow blowers use gearboxes made by COMER Industries. They also supply pto shafts to companies who make farm equipment.

They are an Italian company with distributors around the world but I suspect they don't deal with a guy who wants one of anything, they likely start at orders of 10,000.

I would start looking at new blowers in dealer lots paying attention to the gear boxes until I found a new model which I thought I could make my own look like. Then I would act like a customer who had one of those snow blowers and price a gear box.

Alternatively, look for a used blower that had a strong looking gearbox but is quite rusty and of little value to the dealer and buy it for parts.

My Smyth blower, a Canadian product has a T27D gearbox. Blower is 90" wide and my tractor has 75 HP. A T19-A Comer gearbox has the ability to handle 33 HP at 540 rpm so even it is a bit big for your machine but would be very durable.

Selecting the best gearbox is a job for an engineer who has made a career out of power transmission but copying someone else's work is much easier.

This is not something you are going to accomplish overnight so you have to decide if buying a new blower with a better designed gearbox is the quick but expensive fix or you can pay someone to do your place until you get your own fixed properly.

Dave M7040

 

[Rontay]

Would a damaged gear box cause my 2660 to shut off when PTO is engaged,

 

[Dave_eng]

It is far more likely that a safety switch is shutting down the engine when the pto is engaged.

A damaged gear box would break a shear bolt.

Disconnect the pto and try to engage the pto and see if the behavior remains the same thus confirming it is a safety switch issue.

Dave

 

[Rontay]

It is far more likely that a safety switch is shutting down the engine when the pto is engaged.

A damaged gear box would break a shear bolt.

Disconnect the pto and try to engage the pto and see if the behavior remains the same thus confirming it is a safety switch issue.

Dave

One of the auger shear bolts did break and I replaced it. The chain had some slack and I re tightened it, also when I take the drive shaft off the pto works fine and engine doesn't shut off. Very confused because as soon as the pto tries to engage the auger it shuts off.

 

[Dave_eng]

One of the auger shear bolts did break and I replaced it. The chain had some slack and I re tightened it, also when I take the drive shaft off the pto works fine and engine doesn't shut off. Very confused because as soon as the pto tries to engage the auger it shuts off.

See if you can turn the pto shaft manually when disconnected. Perhaps whatever caused the auger shear bolt to break is still jammed between the auger and the blower itself.

Dave

 

[Rontay]

See if you can turn the pto shaft manually when disconnected. Perhaps whatever caused the auger shear bolt to break is still jammed between the auger and the blower itself.

Dave

When disconnected it does turn with some resistance, I cleared the blower of snow and debris and I don't see anything that would hinder it's operation. Don't know if it matters but it's a bx2750d. Everything worked fine until I went a little deep with the snow on a very uneven driveway and broke the shear bolt.

 

[Dave_eng]

When disconnected it does turn with some resistance, I cleared the blower of snow and debris and I don't see anything that would hinder it's operation. Don't know if it matters but it's a bx2750d. Everything worked fine until I went a little deep with the snow on a very uneven driveway and broke the shear bolt.

If you can get the blower inside where it is warm that would be a first step. Let any ice/snow buildup melt.

If no warm location, make certain you have the correct shear bolt on the fan shaft then engage pto at a bit higher rpm.

Dave

 

[Rontay]

If you can get the blower inside where it is warm that would be a first step. Let any ice/snow buildup melt.

If no warm location, make certain you have the correct shear bolt on the fan shaft then engage pto at a bit higher rpm.

Dave

I found the problem, one of the ears on the fan was bent out and catching the housing. After a few bangs with the hammer it works now. Thank you for your help.

 

[Dave_eng]

I found the problem, one of the ears on the fan was bent out and catching the housing. After a few bangs with the hammer it works now. Thank you for your help.

Great news!!

Thanks for posting the solution as by doing so everyone learns. Too often once a solution is found the owner just disappears leaving us all to wonder,,,,,,,,,,

Dave