rsieminski

Newflee,
I am building a similar sized plane. Wht are the dimensions of the gear you made? Width, height, stance, weight of cloth, etc. They sound strong enough, and stiff enough. Did you use a 2 piece compression mold like I use? The biggest I've ever done were 60-90 sized. This bird will have an MDS 2.18, and I'm making the mold for the props right now.
Thanks,
--Rick

scole

My Feedback: (5)

For a 35% plane i used 7 strips of 5.8oz cloth plain weave regualar cf, and 15 layers by 4 layers wide of 50k tow spread by 1.75". Aprrox. 3 layers of tow and the a layer of cloth. Turned out really strong. No colered kevlar though.

Newflee

Rick,
My gear is a little unconventional in that I adjusted it's construction as I went.
I made a mold from thin ply wrapped over a chunk of MDF shaped with the proper slight bow in the legs as scale on a Super Decathlon.
Then I layed up at least 15 layers of heavy weight hybrid cloth using west system.
After it had cured somewhat I realized that it would not be stiff enough, I layered on an additional 4-5 layers of heavy CF cloth to the open side. Since at this point the gear was rigid enough to remove from the mold I popped it off and layered another 4-5 layers of cf to the underside. This is not ideal but it worked. If I do it again I will do the opposite and sandwich the cf inside the hybrid.
It worked for me but you can do it right if you plan ahead. I would say the best would be 3 layers hybrid, 14 layers alternating cf and hybrid and then finally 3 layers hybrid.
Vac bagging would be ideal as well but I have no experience with that.


Lee

filtr-RCU

Hi David

I looked at your web page. Great info. I was wondering if the expoy you used was west system or another brand. Also is you are making landing gear what are you using for carbon fiber.

davidfee

Hi there,
Actually, the epoxy I've used most is from a company called Jeffco. I get it at a store (Diversified Materials) about 5 miles from my house, or direct from the company since they are also in town. http://www.diversifiedmaterialscompany.com/ http://www.jeffcoproducts.com/

The carbon gear I helped make was for a school engineering competition plane, so we used whatever was available. We had some heavy carbon fabric, either 6 or 8oz stuff. We used about 6 layers of that. We ended up adding some uni-carbon to the gear to stiffen them up since they were flexing a little bit too much with the plane fully loaded (~16 lbs).

-David

scole

My Feedback: (5)

rsieminski: Do you make smaller sized landing gear? If so, what do you use instead of formica for the face of the mold? I have had no luck with formica and smaller gear.

nucmann

What dimentions do you want to make them? What problems have you had with the formica?

scole

My Feedback: (5)

Formica snaps when bent to far, thats the problem. I just need something that bends furthur.

rsieminski

Heat it up with a heat gun and make it to shape before you apply the contact cement. (BTW)You can remove formica with a heat gun as well. The heat reactivates the cement. If you work it, you can bend it around a sm radius.

scole

My Feedback: (5)

Cool, i never thought of that, thanks.

3wExtra

Has anyone made a hollow landing gear?
If so how did you do it?

Jim J

Haven't done landing gear, but either of two ways might lend themselves, the foam core with exterior laid up layers then using appropriate vaccum forming techniques just as in
wing making, or possibly the use of two molds , an upper and a lower each former first ( using vaccum bagging if available, then joining after both molds are done. This joined
"biformed method' could then also be layered on the exterior and vaccum bagged with appropriate release layers (films). I am not sure where hollow would be applicable unless it was a very large structure.
Jim J

scole

My Feedback: (5)

I am going to try and make my LG like that. If i could just find a router bit that would give me a concave/ convex surface you can make hollow LG. It will be much stiffer and weigh less.

Newflee

Personally I would be shy about using a router or anything abrasive to cut a CG part. I am under the impression that disturbing the composite matrix will affect its strength.
Sounds like I'm talking about a movie plot.

I really don't see the purpose of making a hollow structure. I made mine solid with a final weight of 9 oz replacing what was a 18 oz 6061-T6 gear.


Lee

scole

My Feedback: (5)

I'm not cutting into the carbon gear, just the mold.

Basically, by making the carbon skins further apart you are increasing strength a lot. There was a thread a little while ago about that.

Newflee

OK sorry, I misunderstood.
Personally I will be spending my time getting high tech with more critical "in flight" components. I like the solid gear that I made and don't think I could improve it too much. What is your application for the hollow gear? Can't see it being a valuable factor unless you are talking about the ultra light electric stuff. If you are thinking that you can achieve more strength than solid, I don't think it's in the cards.
Share your project with us....don't be a tease.

Lee

3wExtra

you not only gain strength, but the delamination issue should be history.

davidfee

Careful... there's still the chance of delamination around the perimeter.

If you are delaminating a solid composite gear, then the epoxy (or whatever the resin was) is failing... not the fabric. So, my instinct is that more vacuum is needed to get the plies closer together... and possibly a different resin system. Another possibility is that too much vacuum is being used and the plies are resin-starved. It's hard to say without looking at the actual failed part.

-David

3wExtra

the problem with delatination on the gear I have is the it delaminates at the angle. all the stress gets directed to this little area. with a hollow LG you would have to make bigger radius angles which should help to distribute the load to a bigger area.

davidfee

I'd suggest that removing the sharp radius would solve your problems without going to a hollow gear... but experimentation is at least half the fun... so have at it.

-David

scole

My Feedback: (5)

When i finally find a bit i will let you guys know how it turns out.

Jim J

Custom bits are often available at a high end "sharpening" facility.
They can make them out of carbide. Depending on he size shaft, 1/4 or 1/2 inch, you maybe able to use a stock carbide bit and grind your own. Many are single bladed bits and they would lend themselves better to grinding. Use lower speed router rpms with a home ground bit, as balancing may be more critical.
Shops who do a lot of tool sharpening can usually custom grind a bit in most what ever shape you would like.
Jim J

scole

My Feedback: (5)

Thanks, i've been looking at Home Depot, Lowes, Sears....

Jim J

Hi Scole, you might check the list at http://www.wlfuller.com/NY.HTM to see if there is one close to you....the "grinder" ones might be the better options but a lot of the sharpening shops may be able to help you. Good luck. Jim J

Jim J

this one is in Rochester.....
Jackson Saw & Knife Co Inc
517 State St, Rochester, NY 14608
Phone: (585) 546-7485
jj