Help, the vent hole on my GoldenBee plastic backplate opened up.

Marleysky wrote:What was used to plug them up before?  

I don't know, I trew away the little bits I found in the fuel tank. And the engine is almost new (my plane flew around 40 times) so I suppose the backplate plastic is the kind that cannot be glued easily.

The toothpick idea looks interesting. Maybe some U shaped wire (there are two holes) with a blob of epoxy to hold it in place.

If you're using a stunt tank, you'll need to be sure these are completely sealed from air leaks. That's probably a backplate from Cox International and they sealed them I think with JB Weld. Just make sure you get it completely clean and use regular slow setting JB weld again. Make sure it's not JB Quick. I've had bad luck with that stuff.
Rusty

If it were me I would use this stuff Look better and fuel resistance .... https://www.permatex.com/products/gasketing/ultra-series-gasket-makers/permatex-ultra-black-maximum-oil-resistance-rtv-silicone-gasket-maker-4/

I would thread some #0 screws into the holes. But I have extra of those from a different project...

Phil

pkrankow wrote:I would thread some #0 screws into the holes.  But I have extra of those from a different project...

Phil

That's a good idea, and use the oil proof Permatex Eric suggested too. If you have #0 machine screws I'd say tap the holes for a better seal. Or buy another backplate.

Thanks guys.

I'm not sure to find permatex in France. Anyway I will try tp repair the backplate one way or another but will make sure to buy a used GoldenBee/BlackWidow on eBay to salvage the original metal backplate.

I think just about any decent thread sealant or thread lock chemical would work with a screw. I use Loctite products.

Has anyone tried to melt this "backplate type" of plastic with a soldering iron or such? I have two damaged plastic backplates, one beyond repair (busted lugs) and another with an extra hole drilled on it (why? I have no idea), so I may try to make some plugs and "melt" them in the holes. But as usual, this may take a while

The "extra hole" might be for an external fuel tank.  Drilling the back plate is a solution that is easier to undo than drilling the side of the tank.  

I have been temped to try hot glue as it seems fuel resistant.  However the "dual temp" hot glue I have gets soft in direct sunlight and I don't have any true "high temp" hot glue.  I have been using "all purpose" or "craft" type hot glue.

Permatex is a brand of engine sealants. I am sure there is a comparable product available in France or anywhere else in the world as everybody has cars. Key points are "aluminum safe" if it is being used on the metal since regular RTV silicone has acetic acid (vinegar) as part of the curing process which will erode the aluminum, but on the plastic this is not important.

Phil

Thanks Kari and Phil.

Today I glued a U shaped wire into the two holes. The wire fits tightly into the two holes. I have sanded thoroughly and carefully the surface of the plastic backplate to ensure a good 24hr epoxy bond.

If this does not work I will try the "Permatex method".

Sorry to hear of your misfortune Paul.

The engine was purchased over two years ago and, because we do not have access to the mould for a stunt tank backplate, we cut the fuel nipple off the regular version and plug the two holes with the use of a glue-gun. We are unsure as to what the material is but the backplates were moulded with "Delrin 500" and it is quite difficult to get anything to stick to them. We found the glue we use to be OK but it cannot be ruled out that, over time, the glue becomes brittle; especially if left in contact with Nitro for a long time.

On your next order with us, please mention this post and we will include, pro-bono, a new backplate with your order.

Our apologies for the inconvenience.

Paul_BB wrote:Thanks Kari and Phil.

Today I glued a U shaped wire into the two holes. The wire fits tightly into the two holes. I have sanded thoroughly and carefully the surface of the plastic backplate to ensure a good 24hr epoxy bond.

If this does work I will try the "Permatex method".

That should do the job, but in the pic it looks like some glue might be on the sealing rim. If not, I apologize, but if there is you may want to get a paper towel, toothpick, and some acetone and make sure, so you don't have it cause another air leak.

Cox International wrote:Sorry to hear of your misfortune Paul....

On your next order with us, please mention this post and we will include, pro-bono, a new backplate with your order.

Our apologies for the inconvenience.

Customer service excellence. Thanks Bernie.

Hi Bernie,

Thanks for your help. I don't trust these plastic backplates so anyway I am in the process of buying an old metal backplate on eBay.

I am very happy with your company. I love it!

Rusty thanks for the observation. I had wiped out the excess epoxy. The shine comes from the residue.

This reminds me of my control line Cox PT-19 when I was a teen: the plastic firewall used to crack and break.

pkrankow wrote:I would thread some #0 screws into the holes.  But I have extra of those from a different project...

Phil

I don't have any of these plastic backplates.. but small screws similar to what Phil mentions above.. can be found in "eyeglass repair" kits. They might even self-tap their way in. The head design would bury itself flush. Don't know if the thread-length is long enough though?? (They're usually only threaded on the ends)

roddie wrote:

pkrankow wrote:I would thread some #0 screws into the holes.  But I have extra of those from a different project...

Phil

I don't have any of these plastic backplates.. but small screws similar to what Phil mentions above.. can be found in "eyeglass repair" kits. They might even self-tap their way in. The head design would bury itself flush. Don't know if the thread-length is long enough though?? (They're usually only threaded on the ends)

Good call on the eyeglass screws, everybody can get those for a buck or two in those little kits. As long as it is in 4-5 turns it shouldn't matter if the head is buried or the shaft is fully threaded.

Phil

I bet those are even smaller than #0. Is there such thing as #00?... Doublenaught screws lol.

pkrankow wrote:

roddie wrote:

pkrankow wrote:I would thread some #0 screws into the holes.  But I have extra of those from a different project...

Phil

I don't have any of these plastic backplates.. but small screws similar to what Phil mentions above.. can be found in "eyeglass repair" kits. They might even self-tap their way in. The head design would bury itself flush. Don't know if the thread-length is long enough though?? (They're usually only threaded on the ends)

Good call on the eyeglass screws, everybody can get those for a buck or two in those little kits.  As long as it is in 4-5 turns it shouldn't matter if the head is buried or the shaft is fully threaded.

Phil

Yea.. if you do a search for "eyeglass screws" (like I did.. ) there are more variants than there are Cox engine variations.. What concerned me is whether the "garden-variety" eyeglass-screw has an unthreaded-section of the shank below the head, which allows for squeezing the flange that tightens the frame and ear-pieces. The wall-thickness of the backplate is minimal in the area of concern.

Paul's fix looks like it should hold up.. but I don't blame him for wanting to find an original Mazak/Zamak (white-metal) backplate for his engine. The Delrin replacement backplate's weakness is said to be in it's 4 ears for mounting to a firewall. One hard nose-in crash will likely separate the engine from the airplane. It's questionable; whether using wood-screws having a snug fit inside the ears.. and using flat-washers under the screw-heads might help prevent this. I always use flat washers for more support in this area.. regardless.

If your removing/replacing your Bee (radial-mount) engine on a model for any reason.. (rebuild/hop-up/cleaning).. you might find that your mounting-screws won't tighten in the firewall after a few times. This can be fixed a few different ways. You can squirt some thin CA glue inside the firewall holes.. or (if the threads are really stripped-out..) cut the "thin-ends" off of some flat wooden toothpicks.. and drop them into the firewall-holes "flush".. along with a few drops of thin CA glue. This will allow your screw to thread back in to a smaller void which is also strengthened by the wicking of the CA into the surrounding firewall material.

Okay here is an update after two flying days:

The engine works OK.
But the epoxy on the inside of the backplate is already gone. The epoxy on the outside still holds on. I use 12% nitro fuel.
Note: after a day of flying I always remove, disassemble and clean the engine and reassemble it with a few drops of after oil.

Way to Go Paul what are you flying I didn't see were you said ? Any of that epoxy in the engine when cleaning ?

I personally think a small dab of JB weld on outside would be sufficient for the life of the back plate

That said, I absolutely hate the plastic BPs and go out of my way to buy lots of used and mostly junk cox engines JUST for the metal back plates...

Nothing wrong with a "day" of flying!! The epoxy that's actually "in the hole" might stay there for a good long time. I wouldn't worry about it unless it starts to leak. Congrats on the flights!!!

I think if it starts leaking air again, I'd melt that sucker shut with a soldering iron.

getback wrote:Way to Go Paul what are you flying I didn't see were you said ? Any of that epoxy in the engine when cleaning ?

I fly a Little Mediator (1977) from Bob Wallace. In fact the epoxy fell apart when I cleaned the inside of the backplate.

fredvon4 wrote:I personally think a small dab of JB weld on outside would be sufficient for the life of the back plate

That said, I absolutely hate the plastic BPs and go out of my way to buy lots of used and mostly junk cox engines JUST for the metal back plates...

I just bought a NIB Black Widow from the 80' from eBay (with a metal backplate). But I also ordered a plastic backplate. I will mount the BW on the Little Mediator and reserve the GB for the Junior Falcon I am building. I'll add a dab of JB weld (or whatever I will find here that is equivalent) on the outside of the new plastic blackplate that I just bought for the GB.

roddie wrote:Nothing wrong with a "day" of flying!! The epoxy that's actually "in the hole" might stay there for a good long time. I wouldn't worry about it unless it starts to leak. Congrats on the flights!!!

Thanks roddie.

RknRusty wrote:I think if it starts leaking air again, I'd melt that sucker shut with a soldering iron.

That's an interesting idea to be considered, thanks.

roddie wrote:

pkrankow wrote:

roddie wrote:

pkrankow wrote:I would thread some #0 screws into the holes.  But I have extra of those from a different project...

Phil

I don't have any of these plastic backplates.. but small screws similar to what Phil mentions above.. can be found in "eyeglass repair" kits. They might even self-tap their way in. The head design would bury itself flush. Don't know if the thread-length is long enough though?? (They're usually only threaded on the ends)

Good call on the eyeglass screws, everybody can get those for a buck or two in those little kits.  As long as it is in 4-5 turns it shouldn't matter if the head is buried or the shaft is fully threaded.

Phil

Yea.. if you do a search for "eyeglass screws" (like I did.. ) there are more variants than there are Cox engine variations.. What concerned me is whether the "garden-variety" eyeglass-screw has an unthreaded-section of the shank below the head, which allows for squeezing the flange that tightens the frame and ear-pieces. The wall-thickness of the backplate is minimal in the area of concern.

Paul's fix looks like it should hold up.. but I don't blame him for wanting to find an original Mazak/Zamak (white-metal) backplate for his engine. The Delrin replacement backplate's weakness is said to be in it's 4 ears for mounting to a firewall. One hard nose-in crash will likely separate the engine from the airplane. It's questionable; whether using wood-screws having a snug fit inside the ears.. and using flat-washers under the screw-heads might help prevent this. I always use flat washers for more support in this area.. regardless.

If your removing/replacing your Bee (radial-mount) engine on a model for any reason.. (rebuild/hop-up/cleaning).. you might find that your mounting-screws won't tighten in the firewall after a few times. This can be fixed a few different ways. You can squirt some thin CA glue inside the firewall holes.. or (if the threads are really stripped-out..) cut the "thin-ends" off of some flat wooden toothpicks.. and drop them into the firewall-holes "flush".. along with a few drops of thin CA glue. This will allow your screw to thread back in to a smaller void which is also strengthened by the wicking of the CA into the surrounding firewall material.



 

Yes, many, many most from China (Hong Kong etc.) Cheap to buy and ship. I have bought several different types.

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2060353.m570.l1311.R1.TR6.TRC2.A0.H1.Xeyeglass+screw.TRS0&_nkw=eyeglass+screws&_sacat=0