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3 Attachment(s)
Home made propeller
Hi all,
I am giving making a tubed cleaver for a 8hp Tohatsu a go.
Chopped blades of one of my Johnson 25hp stainless props and re-shaped, still a bit of fine tuning on blade shape to go.
Will make a jig and pitch block to weld blades on at 13 pitch and low rake.
Will keep pictures comming.
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3 Attachment(s)
Home made propeller
Hi all,
I Have added a trailing lip to the blades, they all still need to be sharpened and polished.
I have also started on a pitch block (I decided it does not need to be that pretty as I will only be making one of these props)
I have weighed each blade and they are within 1gram (I will also ballance the prop once it is all together somehow)
I am gauging my pitch block off 3 props I have here which are all 13 pitch.
Although I have played, re shaped, modified heaps of props I have never made one from scratch so I am no expert at this, I know full well this could fail but would love any information or help from anyone who has done this before.
Just something I am enjoying playing with.
Cheers,
Glenno
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Another nut like me! (Made several that way.) Be sure to leave LOTS of fillet where the blades are welded to the hub. (I didn't once and--whamo!--the blades broke off.)
Jeff
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Quite a nice project. Do those blades have progressive pitch from leading to trailing edge at any given radius or a constant pitch at any given radius? If progressive pitch how will you get your desired 13" pitch?
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Hi mate,
Yep the blades are progressive pitch the whole way up the blades.
It will be 13 in the centre. I have three props here that are 13 pitch which I am modeling my pitch off, two of those props are progressive pitch.
If I get the pitch a bit wrong hopefully I go down not up, 12.5 would be fine but I am not sure how above 13 would go without modifying the little motor a bit.
If this prop is a failure, hopefully it looks cool and I will put it in my wife's display cabinet to man it up a bit!
Cheers,
Glenno
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2 Attachment(s)
Home made propeller
Hi all,
Just finished the jig for holding the blades as I weld. We will see if it works, I know as soon as you tack weld stainless it moves, I am hoping to get this thing really accurate but at the end of the day if I fail at least I have learned a few more things.
I am wondering if I should polish the hub and blades before I weld it all together so I only have to clean up the welds and splatter. It would be easier while it's apart as it is only a small prop at just under 9 inch diamiter.
Thanks for the input so far.
Any input would be appreciated
Will keep you posted
Cheers,
Glenno
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You'll have a tough time getting a grinding wheel in there no matter how you do it. Be sure to leave at least a 1/4 inch radius fillet weld AFTER grinding or the blades could snap off. (In other words, avoid excessive grinding.) A 1/2 inch fillet would be even safer.
Jeff
PS: Nice fitting of the blades to the hub! You might want to bevel that straight edge on both sides of the blade to improve weld penetration.
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1 Attachment(s)
Home made propeller
Hi,
I will make sure to leave a good amount of weld on for sure, good info Jeff, last thing I want is for it to tear apart.
Just gave all members a quick buff to make final finish easier.
Cheers,
Glenn
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One more thing I forgot to mention: I weigh each blade on a digital scale before welding. The heavy one(s) are ground (over a large area) on the back side to lighten them.
On angular positioning (since we don't own a machine shop!) you can use a large hex nut tack welded to the hub. A pointer aimed at every other flat (where they peak) will give you accurate results.
Good luck!
Jeff
PS: No one is gonna put Ron Hill out of business this way, but it sure is an interesting project. I've built five to date, two of which are successful.