Author Topic: Building your own parts (Read 3474 times)

Randy Powell · « **on:** June 29, 2009, 10:12:16 PM »

Well, my new roll of carbon fiber fabric (5.5 oz structural stuff) came today. Finally found a supplier that doesn't wear a mask and hold a gun when selling it to you. I've been working on anew mold for a carbon fiber bellcrank and am pretty happy with it overall. It's based on Denny Adamisin's old self-neutralizing design. Sort of. Anyway, I laid up the first one tonight. We'll see what I have tomorrow.

One of the things I find fun with this stuff is making your own parts, like bellcranks and such. I take the same view I do when working on my car. A lot of stuff I do myself. some stuff in a pain in the backside and so I let a mechanic do it (I just paid a mechanic to install a gas gauge sender unit in my car - you have to drop the tank to do it and it just wasn't worth it to me. Hey, for a $100 (less the cost of the part - about $55) it was well worth it to let him install it instead of spending a pile of time and skinned knuckles on it)., I usually make my own bellcranks, mold various parts like cowlings and such, make my own fuel tanks and so forth. I buy control horns because, though I can make them, I don't enjoy it much. Sometimes is a matter of cost. It's not worth it to me to pay someone $30 or $40 bucks for a part that I can punch out in an evening. Other times it's a matter of effort or complication level. I'm not a good enough machinist, for instance, to build my own engine form scratch. I can follow directions, but my mill has too much runout to make it practical and I don't really have the needed skill level (though I think it would be a blast).

Some things you do at least once so you learn how, but it may not be worth it all the time. I have made my own venturis (venturii?). But it's kind of a pain and I'd rather pay someone else to do it. same with other stuff. If I ever get the tooling for my lathe, I'd like to try making my own spinner, but I already know it's not something I'd want to do all the time. Same with other stuff.

What standard parts do you like to make yourself?

sleepy gomez · « **Reply #1 on:** June 30, 2009, 10:39:48 AM »

Okay, I'm cheap. I make my own bell cranks and control horns. Bell cranks are made from .220" birch plywood from home depot. All are bushed with aluminum pop rivets. I test bell cranks by lifting 60 pounds of lead off the floor holding by a wire through the pivot. They are light but I don't have digital scales.

NOW I have discovered a new reinforcement material. At least I have never heard of any one using it. Dryer sheets such as Bounce make strong reinforcements. The appearance is that of a very loose weave silkspan. They are made of polyester. Epoxy in place. Some brands are a bit lumpy out of the box. Lay them down and iron them flat. Used ones out of the dryer are just as good as new ones. For a smoother surface epoxy them down and cover with wax paper. Then smooth out and let epoxy set. The ones I like best come from Dollar General. They are Suavitel brand. These are smoother and don't need ironing. I'm sure there are many brands that will work. At a dollar a box for 40 6" x 9" sheets one can afford a bit of experimenting.

Matt Colan · « **Reply #2 on:** June 30, 2009, 01:09:20 PM »

The only thing we make ourselves are fuel tanks, only if they need to be specially made for a plane. Other than that nothing.

Will Hinton · « **Reply #3 on:** June 30, 2009, 03:51:30 PM »

I like to build everything possible except for my bellcranks. I dunno why I don't do those, but I've been using the Sig four incher since it came out. I make my own horns - all types, love molding my landing gears with CF, and if the ship requires a small dimension metal tank I make those. I don't however, make my own tanks for the majority of my stunters - the Sullivan slant is my fav there.
Randy, which supplier did you find for your Cf? I use 1/8 X 1/4 rectangular rods as reinforcement rods in the necks of my custom guitars and they are really WOW in dollar amounts, plus I have to buy 48" rods and I don't need them that long except for the bass necks. Maybe your new supplier will help me out there.
Thanks for starting this thread, it's a subject close to my heart.
Will

Frank Sheridan · « **Reply #4 on:** June 30, 2009, 05:26:05 PM »

The trash can beside the CNC router at work yields raw materials for my projects from time to time. This is a scrap of 3/8" Delrin acetal plastic left after a parts run. When I saw it I thought "bellcranks galore". Only problem is, most plastic bellcranks that I have seen are molded from Nylon like this 3" Sig version. Has anyone ever tried to make one from Delrin? If I were to make a four inch bellcrank, how much tension would be needed to test its breaking strength?

jim gilmore · « **Reply #5 on:** June 30, 2009, 08:10:38 PM »

If I was going to build and stress test a belcrank I would think it need to mounted from whatever mounting point you would mount it. And then weight it to withstand whatever the highest loads it was going to take. Id sqay mount it to a 2x4 put a hook at the back end of the 2x4 to hung from a fish scale then connect extra heavy leadouts to both arms and use the leadouts to lift weights. I'd want to do a lift test and a drop test.
the drop test would be to make sure if it got slack on the lines it wouldn't just break when the plane finally go to the end of the lines again.

Randy Powell · « **Reply #6 on:** July 01, 2009, 11:53:51 AM »

When I designed my bellcrank, I went to my neighbor to stress test it. He's a diesel mechanic and log truck driver. We set it a jig and put it on his press. The first one broke with most of 200lbs of pressure on the pivot, so I think the design is OK. I have since re-designed it and it's got a bit more beef in it. His little press only goes to 350 and it didn't break at that. The jig doesn't work in the bigger one.

Will,

I bought my stuff from Soller Composites. Great services and good quality material.

http://www.solarcomposites.com/

Will Hinton · « **Reply #7 on:** July 01, 2009, 05:09:40 PM »

Thanks Randy, great site!! Now I'm seeing color match CF landing gears, etc. in my pointed little head!!!

Frank Sheridan · « **Reply #8 on:** July 11, 2009, 12:16:55 PM »

This is my finished bellcrank made from Delrin acetal plastic. It's my first attempt at a homemade unit. It started with a piece of 3/8 thick stock. I bandsawed the overall shape, then cut the lightening holes with rotabroach annular hole cutters. The upper and lower spacers are the plugs that came out of the hole cutters. The pivot shaft is the shank of a 1/8" cobalt drill bit. The finished bellcrank is 3/16" thick. The leadouts are an old sullivan C-D set. I'm stuck in the old school methods, so I crimped and soldered them. I was going to bush them with brass tubing but then I noticed the little red tube on a can of WD-40. The leadout wire is a tight fit in the red tubing so I figured what the heck. The action is silky smooth with no slop. That's a Du-Bro 4-40 ball link on the pushrod side. Haven't weighed or stress tested it yet.

Randy Powell · « **Reply #9 on:** July 11, 2009, 11:56:56 PM »

Very nice work!

I just laid up my first bellcrank in the new mold. I'll post a picture later.

jim gilmore · « **Reply #10 on:** July 12, 2009, 06:20:54 PM »

Ok, now we are waiting to see a picture of randys new molded bellcrank. 8-)

Randy Powell · « **Reply #11 on:** July 12, 2009, 07:59:38 PM »

Well, my first one out of the mold wasn't as pretty as I would have liked, but it's solid.

Will, yea, I noticed the various colored CF stuff. So that's how Randy Smith makes those red tuned pipes.

Opps, forgot the most important part: The whole thing, as it sits there, weighs about .60 ounces. Not bad overall.

Frank Sheridan · « **Reply #12 on:** July 12, 2009, 08:06:08 PM »

Sweet! Can we see a picture of your mold(s) - or is that classified info?

Randy Powell · « **Reply #13 on:** July 12, 2009, 08:21:29 PM »

I could probably take a picture. I really need to get some new molding material. The stuff I've been using (Tap Plastics Qwik-Cast) is suddenly having a tendency to bubble if you don't cap the fill holes. Didn't do that before and it could be that it's getting old. Took me two tries to get a usable mold.

jim gilmore · « **Reply #14 on:** July 12, 2009, 09:06:22 PM »

Looks real Nice to me 8->

Frank Sheridan · « **Reply #15 on:** July 12, 2009, 09:22:49 PM »

Just out of curiousity Randy, are you placing your casting material in a vacuum chamber before pouring your mold to remove excess air?

Randy Powell · « **Reply #16 on:** July 13, 2009, 09:08:04 AM »

Frank,

No. Just pouring the material in through vent holes. Point was, it worked fine previously. It's only been the last couple of molds that had problems. I suspect that the material has, uh, aged. I will probably just try out some new stuff and see how that goes. I've made a ton of molds over time. Landing gears (several of those), bellcranks, wheel pants, cowls and other stuff. This is the first time I've had problems.

Frank Sheridan · « **Reply #17 on:** July 13, 2009, 03:30:59 PM »

Randy
I agree with you on the aging chemicals. I've had that problem with epoxies in the past. All the composite stuff we use at work has expiration dates, and we adhere to them without exception. You would not believe some of the stuff I've seen go into the HAZMAT cans for disposal. I'm very interested in molding techniques. If anyone has any good links to some tutorials, I'd like to see them.

Randy Powell · « **Reply #18 on:** July 13, 2009, 04:04:33 PM »

Frank,

Well, I've sort of learned by trial and error. I've used hard molds, soft molds and lost molds at various points. I did a rather involved cowl that the only way to make it work was a partial silicon mold with a lost mold cast in the center. It worked great, but I'm still not sure it was the "right" way to do it. A lot of times, I just think about what I need to do and come up with a process that works out. Much like learning to run a mill (something else I am learning by trail and error and a lot of reading), a lot of stuff ends up in the can as an idea that just seemed like it should work didn't.

I usually do a mold when I want repeatability. Or when I'm just being clever.

Frank Sheridan · « **Reply #19 on:** July 13, 2009, 05:43:23 PM »

Your bellcrank looks good to me. Most of my experience with carbon fiber has been limited to autoclaved panels and prepregs. After years of working with epoxies, I have started to notice a mild skin irritation after exposure. I have seen severe reactions such as facial swelling and breathing problems on other employees. I cannot overstress the importance of personal protective equipment such as gloves, safety glasses and particle masks while working with composites. The best way to get something off your skin is to never get it on you in the first place.

Randy Powell · « **Reply #20 on:** July 13, 2009, 09:18:09 PM »

Frank,

Yea, I always use nitrile gloves. And I use a mask when sanding composite. I'm already sensitized to catalysed polyurethane, I don't need to develop another problem.

Jim Pollock · « **Reply #21 on:** September 23, 2009, 11:09:53 AM »

Hey Ty,

Would you happen to have any extra B'stormer canopies??

Jim Pollock

Jim Pollock · « **Reply #22 on:** September 24, 2009, 04:30:56 PM »

Ty,

You seem to have forgotten that I gave you an airplane when I moved to Virginia. I just need a canopy for the B'stormer I'm building. You also seem to be very defensive about your stuff where I'm concerned without reason.

Never mind, I'll just order one from John Brodak.

Jim