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Building Tips and technical articles. => Building techniques => Topic started by: Chuck_Smith on November 07, 2018, 10:37:56 AM

Title: J B Weld Question Again
Post by: Chuck_Smith on November 07, 2018, 10:37:56 AM
Looking for some info. My ships are .60 powered and up. I'm currently using piped K .77's. I have moved to a new pushrod system with molded nylon inserts for the ends. I've always soldered and the only issue I've ever run into there is corrosion after 10 to 20 years due to the flux never being completely gone. With the new pushrod ends I'm concerned that I'll be able to get the pushrod hot enough for a reliable joint without melting the insert. I use PSP welded and bushed control horns - got quite a stash of them - and my system is to use a ball link on the "driving" end and a 90 bend with a soldered washer on the other. Has worked well for me, and helps with the space restrictions encountered in the elevator horn area of the fuselage.

I see posts about using JB Weld on the retainers in lieu of solder with some techniques to give the surfaces some "tooth". Since the ends of my pushrods are already glued in with JB Weld and then wrapped with CF, I'm thinking the JB Weld retainers on the 90's would solve the melting problem.

Does anyone have any direct experience with using JB Weld instead of solder on larger ships and would you say yes or no to continuing the practice?

Thanks in advance,

Chuck

 
Title: Re: J B Weld Question Again
Post by: bill bischoff on November 07, 2018, 11:17:31 AM
I had some plastic hub wheels that prevented me from using soldered washers on the landing gear. Instead, I cut a groove around the end of each axle, and secured the wheel with a flat washer and an RC car e-clip. They have different sizes, including 3/32" and 1/8". Then I applied a blob of JB weld over the e-clip, warmed it with a heat gun to get it to flow in and around the joint, and left it to harden. Worked great! To cut the groove in the right place, simply put a wheel collar on the wire and cut up against the collar with a cutoff wheel in your Dremel tool.  H^^
Title: Re: J B Weld Question Again
Post by: Brett Buck on November 07, 2018, 11:23:41 AM
I had some plastic hub wheels that prevented me from using soldered washers on the landing gear. Instead, I cut a groove around the end of each axle, and secured the wheel with a flat washer and an RC car e-clip. They have different sizes, including 3/32" and 1/8". Then I applied a blob of JB weld over the e-clip, warmed it with a heat gun to get it to flow in and around the joint, and left it to harden. Worked great! To cut the groove in the right place, simply put a wheel collar on the wire and cut up against the collar with a cutoff wheel in your Dremel tool.  H^^

   I do something similar when attaching pushrods permanently, cut grooves, wire wrap, and then solder. The key is to use a non-corroding flux and don't count on taking much load. NEVER USE STA-BRITE flux! it cannot be effectively removed. JB-Weld or JB-Kwik is probably in the ballpark with soft solder for the sorts of conditions we are talking about.

       The usual ball-link connections, where were warned against by all the experts back in the day, have proven much more reliable than soldered or JB-Welded washers. Some types get draggy, so people are back to looking for alternatives.

    Brett

   
Title: Re: J B Weld Question Again
Post by: john e. holliday on November 07, 2018, 11:52:10 AM
I have used J-B Weld for a long time on pushrods and wheel retainers.  Only failure I had was on the bell crank post in one of my planes.  Didn't cut a notch for the J_B Weld to bite into.    D>K
Title: Re: J B Weld Question Again
Post by: Paul Wood on November 07, 2018, 03:45:13 PM
I have used J B Weld in a lot of applications including mufflers. I've never had a failure. I scuff the surface with something more robust than sandpaper, usually a file or a Dremel grinding stone. Then I clean the area carefully using acetone and a Q-tip to remove the microscopic particles and any remaining oils. (Do not handle the surface with bare fingers after cleaning).

But having said all that, I would suggest you make a few sample parts and test them to destruction to satisfy yourself of the strength. If in doubt, don't do it. Not worth a plane wreck!

Paul
Title: Re: J B Weld Question Again
Post by: Chuck_Smith on November 07, 2018, 04:17:27 PM

But having said all that, I would suggest you make a few sample parts and test them to destruction to satisfy yourself of the strength. If in doubt, don't do it. Not worth a plane wreck!

Paul

Thanks and good advice. Drilling one of these long-cranked engines into the pavement ain't my idea of fun.

Chuck
Title: Re: J B Weld Question Again
Post by: Motorman on November 07, 2018, 05:37:33 PM
Securing control system with JB weld is not something you see on real airplanes = fail. Just use 2 ball links.


Motorman 8)
Title: Re: J B Weld Question Again
Post by: FLOYD CARTER on November 09, 2018, 12:07:34 PM
Notching the wire and then putting on a flat washer with  JB Weld doesn't take advantage of the notch(s) you have put in.  Instead, wrap with small wire (tin coated) so that the wire will sort of fall into the notch(s) and make a mechanical connection first.  The JB Weld then isn't required to bear all the loads.
Title: Re: J B Weld Question Again
Post by: Chuck_Smith on November 14, 2018, 04:42:37 PM
Did some experimentation and the results weren't great.

First, JBWeld doesn't bond to Nylon or flexible plastics worth a hoot. First indication was that after it set up for 24 hours I went to clean up the mixing cup and when I lifted it by the mixing stick there was zero bond. Next, I had a nylon pushrod end that I had roughed up and the JBWeld didn't bond to it at all. If falls off.

Best result I had was to use thick CA and then wrap the ends in CF veil with 30 minute epoxy. Bomb-proof. 

Put a ring around a piece of wire with a Dremel and cutoff, let the JBWeld cure overnight. Meh. I guess in a pinch but it didn't take much to remove it.

Out came the soldering iron for the retainers and now I'll sleep well know my controls are going to last.

Chuck

Title: Re: J B Weld Question Again
Post by: Dave Hull on January 01, 2019, 03:05:35 PM
Bonding to plastics can be especially challenging. And nylon(s) are not easy. I believe that the only bonding material I have seen much success there is EC-2216. Better to use a mechanical system or soldering, but if you need to distribute loads by bonding, check out this material:

     https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-Scotch-Weld-Epoxy-Adhesive-EC-2216-B-A-Gray/?N=5002385+3292667630&rt=rud

It is not the highest strength of the aerospace adhesives, but it is one of the most forgiving, and is used in a lot of applications.

One method in full-scale practice is to cross-drill and rivet the end fitting (plug) into the tube. This might work fine with a carbon tube as well if there is enough bearing area to avoid spitting the tube. If you wrapped the end with Spectra and coat with epoxy, there is little chance of splitting leading to it all coming apart.

Dave McSlow