Outrunner fixing screws

[Glyn44]

I am building an electric model and I am unsure whether I should do the following.

I have come to the point where I need to bolt on the motor, before I fit on the final side of the fuse. This is to enable easy access to the four screws behind the firewall. I realise that once the build is complete I will be unable to get at the nuts of these bolts, if I should ever need to remove the motor. So my question is will it be ok to reverse them so that the bolt head is inside and the nuts are on the outside? If so I can hopefully undo the nuts. I was thinking of a blob of epoxy applied to the bolt heads to make this task easier.

I can't see any disadvantage myself, but what do I know!

[Keith Berriman]

Hi Glyn44 I have used your proposed method and used a large washer under the bolt head to spread the load

[Glyn44]

Ok, that won't be such a problem as the model is a pusher. Thanks

[Geoff Hoolahan]

Hi Glyn44, I think the usual method would be to use captive nuts e.g. **LINK**

of course, other brands are available

[Glyn44]

Yea I realise that but in this case there is just not room for them, as the holes are right in the corners.

[Geoff S]

You could use threaded insets from Modelfixings though the smallest is 4mm.

In the past I have made my own captive nuts by soldering ordinary nuts on to a piece of fibreglass PC board and glueing the PC board to the back of the firewall. To give lots of glueing area use one big piece for all the nuts with appropriate holes for the motor shaft and connections. No reason why you couldn't do the same with the bolts rather than the nuts.

Geoff

[john stones 1 - Moderator]

Grind some off the captives so they'll fit, then epoxy them to stay put.

John

[PatMc]

I'd do the same as Geoff, in fact I did just a few weeks ago, soldered nuts on a piece of scrap PCB then glued that to back of the firewall.

[Glyn44]

Ok I'll try ind find an old pcb,must be something electrical broken around somewhere, I guesse I can't pinch one out of the bosses washing machine, I'm reckon she'll notice.

I have rang a mate who has four 4mm captive nuts I can have. So I'll look at both methods. Sure I'll get around problem with one of them hopefully.

Thanks again guys. I'll post my solution soon as.

[Shaunie]

Hi Glyn,

I suspect PatMc might be talking about unetched PCB. You can buy it from RS Components, CPC Components or probably Maplins. You want fibreglass single sided copper board. With some nuts soldered on and set up so the load is trying to pull the nut through the board it is immensely strong.

Shaunie.

[Glyn44]

Yes Marlins sell it £1:99, but I'm not sure about soldering steel nuts onto it, brass ok, but of course I only have the steel variety.

[eflightray]

You don't say what motor you are using, as many come with, or there are available, 'X' mounts.

So that the fixing screws, (self-tapping etc), are fitted from the motor side, no internal fixings required.

Ray.

[Glyn44]

Indeed the motor will be attached using the supplied cross type mount. I had considered using using woos/self tappers directly into the 3mm ply, wasn't sure it would be good enough, but I suppose with a pot of CA on the thread, and it is a pusher model, it is the easiest solution for me, reckon I'll try it. Thanks.

[Geoff S]

Sorry, I should have said unetched PC board (I still have a stock of scrap from when I retired 20 years ago!). Drill the holes where you need the nuts (or bolts) to be and hold them in place with a bolt whilst you solder then in place. Works a treat.

Geoff

[Shaunie]

Don't worry about steel nuts, they'll be fine unless they turn out to be stainless! Buff the surface with some wet and dry or scotchbrite first if you want to really sure.

If it's a small medel then screws into the ply will be fine but anything sizeable do as you are intending.

Shaunie.

[Glyn44]

No it's a small girl, Nigel Hawes canard the Can Doo:

Borrowed image from the build blog, with thanks:

[PatMc]

Sometimes I have used a scrap of PCB that has enough copper still on but last one was from an unetched piece of old brown phenolic board.

Method I use is to hold the "X" mount in place on an oversize piece of board, drill the mounting holes & centre to clear any protruding shaft etc if necessary. Clean up the nuts with a quick rub on a file or emery cloth. Secure the "X" mount temporarily with the screws & nuts, solder the nuts, dis-assemble, trim the board to the required size. Finaly re-assemble on the firewall with a few drops of medium cyano holding the board to the firewall.

Easier to do than describe.

PS I use steel nuts.

Edited By PatMc on 27/11/2016 21:20:39

[Bob Cotsford]

When we used to use hardwood engine mounting beams we used to solder the bolt heads or nuts to a piece cut from a baked bean can, try that if you can't get the pcb easily.

[Geoff S]

Trouble is, baked bean cans are often aluminium these days rather than tin plated steel

Geoff

[Denis Watkins]

PCB board is very tough and useful, and available from Maplins or eBay, but if you are in dire need, as it is Christmas PM me and I will send you a bit

Edited By Denis Watkins on 28/11/2016 07:24:53

[cymaz]

Solder stout wire to the nuts to join them in pairs. Then ,when the pair of nuts are captured by the bolts, the nuts won't spin.

[Bob Cotsford]

Posted by Geoff Sleath on 28/11/2016 00:30:15:

Trouble is, baked bean cans are often aluminium these days rather than tin plated steel

Geoff

I guess that's progress for you , no consideration for minority interests. Colman's mustard tins - not them too?

[kc]

Take a magnet when you go shopping for tinned food! Some cans seem to be steel including Heinz & Colmans.according to a magnet tried in the larder today.

Actually it is possible to make hexagon nuts captive in wood simply by pulling the nuts into the ply ( without washers) with a bit of extra force.   Or by counterboring with a drill equal to the diameter across the flats of the nut.   Not necessarily recommended for motors but handy for making larger woodwork like jigs and benches.

Edited By kc on 28/11/2016 11:16:19

[Glyn44]

Ok brilliant tips as always, it's easy when you know the answers. Oh just checked and Branston baked beans and Ambrosia rice pud. steel tins.

[Bob Cotsford]

Yes, though these days they have some sort of inert coating that needs to be rubbed off with a bit of sandpaper. Something to do with preventing Botulism or the like.