Using Pipe as a shaft?

[ChristianHF]

Anyone have any experience using 6 to 8 inch schedule 40 pipe as shafting? I am working on designing a poor mans harley rake, given that the shafts typically run at only 250 rpm I am curious if this would be a suitable application for this? Would it be straight enough? I know its going to have a weld seam on the inside and balance may be compromised but I am thinking this would be minimal to non-existent at this low RPM. I have to imagine that manufacturers of these types of implements must use pipe or some kind of welded seem tube for their equipment? I have priced large diameter DOM tube and it is VERY expensive, a piece long enough for a 6 foot rake is nearly 1/3 the price of buying the rake new! Any help or experience you all could provide would be helpful. Thanks.

Chris.

 

[Tractor Seabee]

Looking at pictures on the net it does not appear that there is much center loading. Any idea what force develops in the center? I think you might get by with schedule 10 pipe if weight is a factor. Schedule 40, 6", 6' long weighs 120#, 8" is 180#. For this type rake does is its performance a function of its weight? It will take a lot of force to flex either 6 or 8" pipe. Is a factory unit cast with those teeth or or they welded on? I would run the shaft all the way through to make line up easier. It could be pipe with a solid piece of shaft welded in each end. Looks like a fun project.

Ron

 

[jenkinsph]

I suspect pipe with the proper wall thickness is what the manufacturers use to build their drums. I have looked for the carbide teeth before but never found where they would be available, curious what you plan to use for this.

 

[npalen]

kennametal weld on carbide teeth - Yahoo Search Results
Search based on Kennametal carbide....

Nominal Wall Thickness Pipe
Looks like 6" schedule 40 shows about 9/32" wall and the 8" is about 5/16" wall.

 

[BHD]

just did a picture search, as I did not know what a Harley rake was,

came across this web site Harley Rake, Tractor PTO, T-6 Series 6' Power Box Rake picture at bottom, of page, but one can see they used about 6 to 8 inch pipe about 1/4" wall had two donuts turned of steel and put a shaft in and welded it up,

I took a part a old sugar beet toper, basically a huge flail mower, and the main flail drum was a heavy pipe with ears welded on it for the flails (I took that part and planted it so the cows had a scratch post).

pipes are used in that manor a lot, a two end pieces and some times, a unit cut for the center support, if welded it is usually plug welded, and a shaft for bearings extended through the middle of the pipe, and welded to the supports

another site drawing is from is from one can see by the drawing it is a pipe

 

[BHD]

could not get a second picture to take

 

[npalen]

I've considered building a Harley type rake also due to the high prices. Not sure what makes them so expensive other than they probably have to be built heavy to be effective without self-destructing. The teeth need to be replaceable either by kwik-change or remove and weld new tooth to drum.
While realizing that the angle capability is important I have to wonder why a roto-tiller couldn't be converted to a Harley type rake. I suppose that high RPM (well beyond that of a tiller) is important to get the aggressive cutting action. The weight, RPM and resulting inertia of the drum rotation is probably paramount to the smoothness of operation.

 

[ChristianHF]

From all the literature that I have read the drum/shaft only turns at 250 rpm or less. My plan was to use a 1 to 1 right angle gear box and then use a toothed belt at an ~2 to 1 drive ratio to take the 540 RPM down to 220. I considered using the carbide teeth and I may eventually go that route but I think initially I am going to make the teeth out of AR400 and hard face the "cutting" edge.

 

[npalen]

Good idea on the AR400. Lot less cost up front and you could always switch to carbide later. I agree that the RPM is relatively low, just faster than a rototiller I would guess.
You might check on the availability of "oil field reject pipe". We used to buy it in quantity and a much reduced price. The quality was normally acceptable but had to occasionally reject a stick of it. Defects were normally cosmetic which wouldn't be an issue for a shop built unit. I would think that the difference in rotor diameter could make a big difference in horsepower requirement. Looks like a larger rotor would tend to be more stable when running deep. Not sure what all dynamics come into play though. The amount of dirt that is thrown back over and out of the way would be a factor.

 

[ishiboo]

I've considered this as well. I have NO IDEA why harley rakes are priced as crazy as they are.

One option for the teeth I considered were grade 8 hardened bolts. I don't have a HUGE volume to do like a landscaper, and I think they'd hold up fairly well double-nutted and Loctited (auto-correct turns this to lactated!) to nuts welded to the cylinder, and they'd be easy and inexpensive to replace. If that didn't work, you could then weld carbide teeth to them.

I don't think carbide teeth are necessary.

As for balance, I don't think the weld matters much... you'll need to balance it when you're done anyway for smooth running unless you got the teeth perfect. And since it's contacting the ground, maybe it doesn't matter?