Spinner Backing Plates

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Postby nightwave51 » Mon Apr 26, 2004 9:21 pm

Hi
Does anyone know where I can get new backing plates for the prop spinners? If not , does anyone know what grade of aluminum they're supposed to be made out of . I am a machinist so I can easily use the old ones as a template if I know what grade aluminum to use.
Thanks, Mark
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Postby b diedenhofen » Tue Apr 27, 2004 12:16 pm

You can get them from the Lazairforce website. I purchased a couple this winter, they look fine, bit of a process to install them properly, if they're not centered exactly, they'll likely crack again. I saw an installation instruction on one of the sites, but I can't remember which. It's either the Lazairforce site or the Lazair group on Yahoo. It won't take much of a search to find it though, and it was pretty straightforward.

Brian
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Postby b diedenhofen » Tue Apr 27, 2004 12:18 pm

Just a thought Mark, if you're a machinist, would you be interested in making up a few velocity stacks? I think there are a few of us who could use one or two.

Brian
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Postby rob kerr » Wed Apr 28, 2004 4:08 am

I've got to spin up some velocity stacks at some point this summer.Just have to pick up the right size aluminum and get to it.I figured someone would need some, so I plan a couple extra's.
Rob Kerr
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Postby b diedenhofen » Wed Apr 28, 2004 8:57 am

Fantastic!, put me down for two.

Thanks,
Brian
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Postby Shannon » Wed Apr 28, 2004 3:11 pm

The OEM Rotax 185 velocity stacks where made with a tube flaring machine. The nice outer flare on the end of the stack is the first phase in making the perfect 90 degree flat flange on the other side.

Before getting some heavier stacks "milled" I would do an intensive search for a machine shop with tube flaring capability. It is all together possible that some lightweight copies of the OEM's could be made. Cost would be the determining factor to have some made of course. Just my opinion but the threads in the carburetors may be a bit weak for heavy spun stacks.

There are quite a few machine shops that claim tube flaring capability on the internet. Type in "Tube Flaring" and see what comes up.
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Postby Chappy » Fri Apr 30, 2004 8:57 pm

Shannon,

If I had a larger Lathe, I think I could form the velocity stacks using a method similar to what they do at your link. Anyway, thanks for the link, it's got me thinking about possible ways to make them in my shop.

I could machine them from bar, but they would be awfully heavy, and I would be concerned too about overstressing the mounting screws. Machined velocity stacks seem to be a very popular accessory for all the new little 2 cycle scooters on the market, and they have little bitty carbs with small screws. It appears they are looking basically at smoothing the airflow into the carb with stubby stacks, were as we are also looking to protect the fuel standoff from the prop blast, etc. as much as possible using long stacks, therefore perserving the proper fuel mixture. Long machined stacks would be rather massive. Besides, bar stock is expensive!

Chappy
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Postby Guest » Sat May 01, 2004 12:02 pm

Hi
I guess you figure machined stacks would be to heavy.maybe so.It would be tricky to make them real thin.
I wonder if it might make more sense to make them out of fibreglass.It wouldn't be hard to make a 2 piece mold and wrap them.Certainly be cheaper and quicker for larger #'s
I'll give it some thought.

Rob
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Postby Shannon » Sun May 02, 2004 8:36 am

Stack pic
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Postby Chappy » Sun May 02, 2004 10:16 am

Shannon,

I would think that trying to make the stacks out of 6061 (-T6) would be almost impossible, as the aluminum will work harden very quickly anyway. IMHO, I would use a very soft tube like 5052-0. From looking at the one remaining velocity stack that I have in my possession, and considering it is twenty years old, I would think that the fact that it still has a nice shine to it would support that opinion. I would expect that if it was made from a high strength alloy like 6061, that it would not have retained the pretty finish without any care all these years.

Of course, I could be all wrong!

Chappy
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