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Why the taper shaft?


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#1 Boss 448 OFFLINE  

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Posted December 01, 2011 - 09:54 AM

OK, here's a question for you. Why do the engines intended for generator and refrigeration service have taper output shafts on them? See example http://www.ebay.com/...tem20bf1950b7 .

The engine shown at the link appears to be a great deal for someone that can use an engine of that size though it would require fabricating an adapter for the output shaft. My guess is that the reason for the taper shaft is that generator heads and refer compressors apparently have a critical alignment issue when attaching to the engine and are precisely machined to the taper shaft specs to assure proper clearance and fit when assembled. Does this sound right? I have searched for an adapter to convert the taper shaft to a straight shaft but have not found one. Since I see a lot of used air-cooled diesel engines for sale it would be nice to have a source for such a conversion adapter. I have found specs for the taper but I'm guessing that the cost of machining a one-off would be expensive.

JN

#2 JDBrian OFFLINE  

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Posted December 01, 2011 - 10:59 AM

With Generator sets it allows the use of a 1 bearing generator. In other words the generator shares the crankshaft bearing with the engine. The tapered shaft and socket make about the simplest possible coupling for this setup. I'm not sure about compressors. It is a major impediment to repurposing these engines.
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#3 olcowhand OFFLINE  

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Posted December 01, 2011 - 11:54 AM

Find a junk generator head with same internal taper. Cut off required amount of the generator shaft, then have machined down to fit the needed pulley. Then have a keyway machined into it. Slide this on, then get a high grade bolt of right length & thread to snug her up on the crank. Then you'll be ready to go for either pulley or drive shaft use. If the shaft isn't thick enough for full depth of keyway, you can cut a shallow keyway into it, then mill down a key to fit.
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#4 Boss 448 OFFLINE  

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Posted December 01, 2011 - 01:12 PM

Find a junk generator head with same internal taper.


That's always been my thought, though if someone took the time to design an adapter I wonder if they might find a market for them.

The shared bearing concept makes sense. It does make the engine rather application specific, but then the engine manufacturers are building their engines to the needs of the original buyer - not us looking to repurpose the engines later. I know some engine manufactures offer models with switchable output shaft stubs, but I don't think you will see many of them out there since it is an added cost option where again the original buyer would go the lower cost route with the engine spec'd to their own needs.

JN

#5 Guest_ACguy1994_*

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Posted December 01, 2011 - 06:39 PM

tapered shafts are just to p us repowerers off.

#6 Alc OFFLINE  

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Posted December 01, 2011 - 07:30 PM

Just a few questions on these taper shafts . What kind of adapter would need to go on the shaft ? Like a PTO flange ? How big around is the straight part of the shaft ? Thanks , Al

#7 Boss 448 OFFLINE  

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Posted December 02, 2011 - 10:10 AM

Here is a chart of different output shafts from a Hatz engine manual. As you can see there are a variety of different taper output shafts so this should be useful to people when they are shopping around for a used engine.

output shaft.jpg
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#8 JDBrian OFFLINE  

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Posted December 02, 2011 - 11:09 AM

Thanks for the chart Boss. There sure are a lot of sizes and tapers.

#9 Boss 448 OFFLINE  

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Posted December 02, 2011 - 01:10 PM

I think that the number 1 and number 3 taper shafts are the most common but you can see that it is something to take into consideration.

I think that it is possible to machine adapter sleeves or hubs for most of these though I'm guessing it would be a bit of a challenge. As suggested earlier the other alternative would be to obtain an old armature or hub and convert it.

I don't think that this is necessarily a deal killer on engines with that style of output shaft but I do think it is an important consideration. If a conversion is required (especially if you have to pay for it to be made) it becomes part of the overall cost of the conversion.

JN

#10 MH81 OFFLINE  

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Posted December 02, 2011 - 07:46 PM

Could the shaft be tuned down and a sleeve put on?

#11 Alc OFFLINE  

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Posted December 02, 2011 - 09:21 PM

This may not be the correct flange for what your looking for but could give you some ideas. It has a .750" bore to start but can be bored to 1.688" I don't believe a machine shop would have a hard time to bore a taper for you . Not sure if the bolt on the crankshaft alone would hold it tight enough from spinning or maybe even using the set screw hole with a dog point set screw could do the job .

Automotive Aftermarket Catalog - MyCarParts
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#12 skyrydr2 OFFLINE  

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Posted December 03, 2011 - 06:16 AM

Because it is a relatively short taper, you can do it easily with the compound on a lathe, easy peasy.

#13 Boss 448 OFFLINE  

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Posted December 03, 2011 - 08:19 AM

Fortunately the China 10 HP diesel I have acquired for my first project has a straight shaft so there will be no adapter challenges (I hope). Still, I keep the taper issue in mind in case I run into an irresistible deal on a used engine with a taper shaft. I have seen them out there so it is a very real possibility. I think the input everyone has contributed to the collective knowledge of the subject so I hope it has helped others also. Thanks guys!

JN

#14 Boss 448 OFFLINE  

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Posted January 02, 2012 - 01:40 PM

Perhaps this hub adapter for a Kubota engine might be helpful to someone.

Cub Cadet PTO Clutch Hub for 882 782D 1572 1512 1772 Kubota Diesel 703-0971 | eBay

JN

#15 TUDOR OFFLINE  

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Posted January 03, 2012 - 02:28 AM

Tapered shafts transmit torque without using keys. A drill press with a #3 morse taper will transmit enough torque to drill a 1" hole in heavy plate using nothing more than drill point pressure to jam the tapers together. I believe generators and reefer units are bolted to the engine block to accomplish the same task as well a to maintain alignment.

I noticed that all the cranks in the chart were tapped for retaining bolts for other applications. Heavy industry also uses tapered shaft motors with flanged couplings to mate to their load. The coupling half is retained by a nut on the ones that I saw. Can't remember off hand if they also had a key slot or not.




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