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Ron’s HeliProz South . Century Helicopter . MTA Hobbies

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Gasser Model RC Helicopters > Best tool for Zenoah crank taper
 
 
Fixit
Key Veteran
Location: UK

I would like to machine a fan to fit the Zenoah range of engines preferably in a lathe, I have heard of a tool being made using the crank itself but I'm not sure if it would work or last.

If you have any info on the method and tools in need please let me know.

Cheers
07-05-2008 05:08 PM
HOMEPAGE  
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

You need some type of machine tool to insure precision otherwise what you end up with would be useless. It would not run true. A lathe would be my first choice.

Ace
What could be more fun?
07-05-2008 09:41 PM
 
 
Fixit
Key Veteran
Location: UK

Thanks Ace, I have a lathe but I have no idea what tool to use.
07-05-2008 11:39 PM
HOMEPAGE  
 
 
pgkevet
Veteran
Location: surrey UK

...can't you just put a drill of the correct taper in the tailstock? Or drill a pilot hole then mount a cutting tool at the appropriate angle to form the taper afterwards?

pgk
07-06-2008 12:02 AM
 
 
Fixit
Key Veteran
Location: UK

Quote 
...can't you just put a drill of the correct taper in the tailstock? Or drill a pilot hole then mount a cutting tool at the appropriate angle to form the taper afterwards?

Well if I new how I could I don’t know the correct taper or the depth and setting up a cutting tool wouldn’t be very accurate if I did it I really need a taper tool to fit in the tail stock with some kind of stop on it.

An old crank with a slot cut in the taper end would be ideal if it’s possible to machine a cutting edge on the slot, it could also have a washer welded further down for the stop.
07-06-2008 01:44 AM
HOMEPAGE  
 
 
ka6fty
Senior Heliman
Location: Sacramento, Ca.

I think I would drill it slightly undersize, then use the appropriate reamer to machine it to the finish size.

Example of reamers: http://www.use-enco.com/CGI/INPDFF?...PMITEM=891-4729

"Don't put your fingers where you won't put your face"
07-06-2008 01:44 AM
 
 
shawmcky
Senior Heliman
Location: Isle of Wight,United Kingdom

Taper

Hi Fixit.if you measure the taper on your crank with calipers at the narrow end and then at the bottom wide point and the distance between the widest lower point and top narrow .You can put this diagram on paper and use a protractor to work out the angle in degrees.A local machine shop would probably tell you how to achieve this and what tool to use.
07-06-2008 08:27 AM
 
 
shawmcky
Senior Heliman
Location: Isle of Wight,United Kingdom

Run out

When you mount the tool and fan hub in your lathe you must check the run out of the tool or cutting bit in the chuck with a dial guage.If the lathe is old it might have some runout present in the chuck any way.
07-06-2008 08:43 AM
 
 
nitro fun
Senior Heliman
Location: wilmington ca

put the old pulley onto the lathe, then dial indicate the pulley, adjust the top part of the lathe to the angle of the pulley, then you can put a bit onto it, center the bit, then cut that same angle
07-06-2008 09:22 AM
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

Quote 
Well if I new how I could I don’t know the correct taper or the depth and setting up a cutting tool wouldn’t be very accurate if I did it I really need a taper tool to fit in the tail stock with some kind of stop on it.

I hate to tell you this but you are implying that you never used a lathe before and you picked a very critical part to start with.

PGK is correct it must be a single point tool mounted in a compound set at the right angle.

This is what I did: first you make a gage out of aluminum by cutting the taper in a shaft and then trial fitting it to the crank that you have. If the taper is wrong then it will either make black marks at the beginning of the hole or at the bottom of the hole and that will tell you if you need to increase or decrease the angle of the compound. You keep this process up until you can get nearly full contact with the taper on the crank. Now you have your compound accurately set so you can make the real part that you want. Be patient its a long process.



Ace
What could be more fun?
07-06-2008 03:22 PM
 
 
victor55ca
Senior Heliman
Location: Vancouver BC

When I ordered my engine from Hanson I think Al told me its a 1/5 taper. I am not sure though.

So the angle is arcTan(1/5) = 11.309933 degrees or 0.19739556 radians.
Does this sound about right?

Vince
07-06-2008 03:52 PM
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

Mine came out between 5 and 6 degrees. Eleven degrees sounds kinda much for a taper. I think a Morse taper is somewhere near 7 if I remember right.

Ace
What could be more fun?
07-06-2008 04:22 PM
 
 
victor55ca
Senior Heliman
Location: Vancouver BC

A direct measurement off a crank would be the best method to get a good starting point. Best to do what Ace says to get an exact match.

http://www.gizmology.net/tapers.htm

Vince
07-06-2008 05:09 PM
 
 
Fixit
Key Veteran
Location: UK

OK yes this is the first time I have used a Metal Lathe but I have owned and worked on a 6ft copy lathe for years so I do under stand about compound slides and so on,
It's an old lathe and there was a broken back gear and loads of play everywhere so I stripped it down and I’ve just finished rebuilding it, there’s still some slight play on the cross slide but its in the screw thread and not the dovetail guides so I should be able to shim that.

I have a small boring tool that will probably do the job but I was hoping to do away with setting up and doing test cuts every time I want to do a taper and that’s why I would rather go for a taper tool in the tail stock and offer it up too the fan in the chuck.

Ace, in your picture you have a length of alloy stock in the chuck without surport at the tail end, I’m finding it imposable to true anything up in the three jaw chuck does this mean its had its last day and need replacing? Also your jaws are the opposite way to mine is that what I’m doing wrong/

07-06-2008 06:32 PM
HOMEPAGE  
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

Quote 
Also your jaws are the opposite way to mine is that what I’m doing wrong/

No, no, no I knew I shouldn't have posted that pic. I was in a hurry and just mocked up the set up. Those jaws are wrong I was just trying to show a piece of stock and the compound. I was hoping you wouldn't look to close because the angle is wrong on the compound also.

You have an old lathe. That's like using my tinker toy chinese lathe. But your three jaw is probably large enough to pass the stock right through the center so you don't need to support the work end like I do. The point is don't even attempt the tapered reamer method. It will give you nothing but aggravation. Single point tool is the way to go. It doesn't matter if the screw is sloppy. You can get very accurate parts from that lathe but it will cost you time, that's all. Your finish cuts should be light and your tool should be sharp. I have to take three or four passes with out moving the cross slide because my chinese lathe is so cheesy. But in the end it all works.

Remember, patience. When you are done you will be recommended for sainthood. That's another reason why old timers were so good ... patience.

Ace
What could be more fun?
07-07-2008 02:13 AM
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

opps, I see your pic. What are you trying to do? the stock you have looks about a foot long and maybe 2 inches in diameter. The taper on the engine crank is less then three quarters so a 2-3in by 3/4 dia. is all you need for the gage. It also looks like plastic stock. Don't make the gage out of plastic.

Ace
What could be more fun?
07-07-2008 02:20 AM
 
 
golfietis
Heliman
Location: Kaunas, Lithuania

Quote 
AceBird
Mine came out between 5 and 6 degrees. Eleven degrees sounds kinda much for a taper. I think a Morse taper is somewhere near 7 if I remember right.

Divide 11.309933 degrees by 2, and you`ll get your "between 5 and 6 degrees"....
07-07-2008 06:22 AM
 
 
ozghost1952
Heliman
Location: Melbourne Australia

Best tool?

One of the guys I fly with is a precision machinist - and made me this tool for reaming out fans to suit the Zenoah taper.

Just "drill" a hole in the fan to the inner diameter - insert the tool to the depth of the taper - and the job is done.

I suppose he got tired of me asking him for a favour - so he made the tool to get me off his back!!!!

Jeff

07-07-2008 10:30 AM
 
 
Fixit
Key Veteran
Location: UK

Quote 
I suppose he got tired of me asking him for a favour - so he made the tool to get me off his back!!!!

Nice tool, Can you do me a favour
07-07-2008 11:22 AM
HOMEPAGE  
 
 
cfranks
Veteran
Location: Adelaide South Australia

I had an old engine and cut the crankshaft off. Mounted it in a collet chuck and set the lathe's cross-slide to it. Used it to make the double tapered brass collet in the Vario Benzine clutch.
07-07-2008 10:31 PM
 
 
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Gasser Model RC Helicopters > Best tool for Zenoah crank taper
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