advice required

[Henry Gelsthorpe]

My hobby is mainly in model aviation,recently i have become interested in autogyros.The problem with autogyros is that you have to make 3 rotor blades(accurately).Model autogyro blades can vary in width(chord) from 2" on a small machine to 3.5" on a larger machine.The blades are usually made from all balsa or balsa/ramin/spruce composite.The maximum depth of the blade would be 0.5".I have produced blades in the past by a combination of planning and sanding but it is very time intensive.My question is this, would it be possible to produce blades using a table mounted router? and could the router be used with a cutter up to 3.5" long and cutting depth of 0.5".If a router could be used do any companys out there produce custom router tooling given appropriate cad file data.

[ubeaut]

In my humble opinion it would be a foolhardy and extremely dangerous exercise.

Cheers - Neil http://ubb.ubeaut.com.au/ubb/smile.gif

[derekcohen]

Henry

Neil is correct - potentially VERY dangerous! Don't go there.

Derek

[Henry Gelsthorpe]

Thanks for the reply Neil and Dereck.However as I am new to routing could you spell out in more detail what is fundamentally wrong with the idea.Just in case I have not conveyed my intentions clearly I will elaborate.What Iwould like to do is pass a length of balsa wood past a table mounted router using fences and guides to produce an airfoil profile surely this is little different to say producing a wooden moulding?.Does a composite blank introduce problems with the cutting ?is a 3.5 " high cutter too large for the larger routers?
I appreciate all power tools are inherently dangerous if used incorrectly,that is why I have contacted this forum to get a knowlegable opinion.

[Eastie]

I’ve got a tad bit of an idea of what you’re up to – and without putting to much thought to it - it does sound dangerous.

For starters a 3.5” (vertical) cutter is longer than most if not all common router bits on the market – for good reason. If it is a 3.5” radius cutter similar applies. It really is the realm of purpose built spindle moulder cutter heads. If you are talking of a 3.5” long bit a significant problem is the stress the cutter would go through at such a distance from the collet, not to mention the forces required to accurately and safely introduce and guide the material past the cutter – something that can be overcome with an automated feed on spindle moulders.

With a lot of thought, caution and a fair investment in jig components you may be able to do it, but on face value it sounds dangerous.

[John Saxton]

Henry,whilst it has been declared a dangerous exercise it may not necessarily be so given an approach from a lateral aspect.
If you intend to produce these in number then may I Suggest you approach the idea from an engineering perspective.
Do some research on computer aided design for Jigs/profile cutting with the folk who in the wood industry use computer controlled routers.
They may be able to produce a jig for you to be able to safely produce the propeller blades you require.
Cheers http://ubb.ubeaut.com.au/ubb/smile.gif

------------------
Johnno

[mikmaz1]

hi henry,
these are just a few suggestions i thought of
1... cutting out the basic shape with a scrollsaw, and instead of planing and sanding how about using a bobbin sander to do final shaping. (leave on some extra wood at the ends for finger holds ,then cut of afterwards.)
2... this is a long shot , try and find somebody in your area who has cnc wood machines and see if you can make an arrangement with them!
a few ideas to play around with.
seeyasoon mik.

[derekcohen]

Henry

If I was to shape a prop, especially one from a soft wood such as Balsa, my tool of choice would be a SPOKESHAVE.

Derek (in Perth)

[Henry Gelsthorpe]

Thanks guys!
I now understand that a 3.5 " cutter would take me into the realms of spindle moulder
(shaper?).If the chord of rotor blade (not a
propeller since pitch of blade and section remains constant down length of blade) were to be reduced to say 2-2.75" would that put in the realms of router capacity?.
A spokeshave would be probably o/k for one off situations but i am contemplating a commercial situation.

[Eastie]

The longest straight bit produced by CMT is 2", both in straight and solid carbide spiral flute bits - gives a good indication of the maximum safe length they are willing to put on the market.
Researching cnc machining would be well worth you while.

[Doug Baird]

Hi Henry

Have you at any time given though to using ,fibre glass or carbon fibre ??I am into biulding radio controlled yachts and do a lot of vacuum work and get the hulls down to about .6mm thick if you have a prototype of the article you want, why not make a mould and use this type of medium ( glass/carbon ) and retain all fingers at the end of the day.
Regards Doug Baird

[soundman]

I think the problem is in the asumption that a large cutter is required.

Or for that matter a router is the appropriate tool.

If you are looking at serious production quantities some form of cnc is going to be the only way to go.

Most cnc machining uses a cmall cutter of some form to make multiple passes to achieve a continious form.

You are probably looking at some form of cnc lathe as to use a router plotter will require turning the blank over......

Either way what you are talking about is verrrry serious engineering.

there are probably specialialised machines in the full sized aviation industry to do this sort of work, maybee some investigation there is needed.

There have been mechanical marvels to turn strange shapes like klogs, saddle trees, and other "not realy round" items for many years have a look there.

Againg you are talking verrry advanced engineering here.

cheers.

[Wayne Davy]

Hi,

You could look at making your own small desktop CNC machine using a Dremel. There are quite a few pages on the web regarding making one. Here is one I found which looks interesting

http://www.crankorgan.com/morph.htm

Unfortunately, the guy will only sell the plans in US or Canada.

Cheers,

Wayne