Roxey Mouldings 7G40-18 gearbox

 

In the box with the Sentinel is this gearbox from Roxey Mouldings. Like most of these sort of things, it folds up from flat. One slight difference is that one side is seperate, and soldered on then ready. 

Everything lined up perfectly, and the tabs dropped into their slots with only a tiny bit of wiggling. The bearing holes had to be opened out with a tapered reamer, as I would expect, but the whole job only took a few minutes. There are slots for the screws in the motor, and these benfited from a few strokes of the file to open up. Some Blu-Tack in the screw heads was also helpful.

There are some really nice features such as access holes for the grub screw in the work gear. 

Turning the motor over by hand, everything is super smooth, and all feels solid. 

The only problem is that the sides are only a couple of mm smaller then the Sentinel wheels. That's not going to work. I'll have to find another home for it, and an alternative drive train for the loco. So, it's going back in the box for a while to let me figure it out...

Well, that's not going to fit.

 

Exactly how the Sentinet should be powered, has always been a mystery. The is a motor, and a gearbox, and a pair of motor supports in the chassis. The only support one end of the motor though. 

Anyway, I robbed the gears from the 'box and assembled them, and the motor, into the chassis as best I could. Initially, it looked promising, but sadly, the gear wheel is too large, and rubs on the motor support. A couple of mm and we'd be good to go!

OK, squeezing the Delrin gears would be "interesting", but I think they might just have cleared the motor.

Sorting out the bearings

 

Nice fat things O gauge bearings. Plenty of lovely brass. 

Pity most of it gets filed away. 

First, I reduce the thickness standing proud of the frame side, so the back of the wheel has a tiny amount of side slop. We don't want it running on the bearing, increasing friction. 

Them a reamer is used to open up the hole. I'm sure this sounds odd, but the holes are normally, slightly smaller then the axle diameter. This alloows them to be opened up so the wheels spin freely. An added advantage is that if the bearings aren't perfectly in line, the long broach will line the holes up. 

All that brass swarf, it does seem a bit of a waste, but I'll trade that for good running.

Axle worms

 

Finally, some spare time to have another tinker with the O gauge Sentinel shunter. First time since November last year!

All the wheels and axles were looking a bit rusty. I think I'd missed some flux cleaning on the chassis, and fumes in the closed box has affected the surface. A hour with mild abrasive, a fibre pen and even Brasso saw them restored to good condition, at which point I noticed something odd. 

Each axle has a worm on the end, for the wheel to screw on to. The other is plain for an insulating plastic bush to slide on. 

I've never seen this before, and can't think of any good reason for it. Surely, some of the time, the wheel is rotating in a way that will unscrew it from the axle? I suppose a shunter is likely to travel as far backward as forward, but I just see the wheel coming off at some point, or at least unscrewing enough to make trackholding tricky. 

Can anyone explain? I'm confused.

Cleaning up

 

In the last three weeks, progress on the Sentinel has amounted to an hour of cleaning up the soldered joint around the base of the body. 

While there wasn't much solder, a neat right-angle here will make the model look a lot better, so I set to with scrapers and fibreglass pens to remove any excess metal. A bit of care is required to avoid scratching the brass, but that's mainly angling the metal scrapers sensibly. Then letting the fibreglass do it's job. I'm always amazed how effective this is at burnishing away everything but the brass. 

If I ever get as far as priming the model, hopefully this effort will be worth it because you won't see anything!

First end on

 

Here we go. 90 minutes of tacking metal in place with the electric iron, followed by lots and lots of checking with a square to make sure everything was in the right place was followed by a quick blast with the gas torch to fix it down. 

Followed by more checking to make sure it really was where it was supposed to be. 

I usually say that I can probably build any kit, because I'm not afraid of bodging. Indeed, I'm quite adept at it. The side positioning problem is the sort of thing that would have scared off a beginner, but with care, I've sorted it out. It can be done. 

And it might explain why the kit was cheap in the first place!

The perils of old etched brass kits

 

Oh, you think this kit building lark is so easy. Heats some solder up, chuck it in the box, give it a shake, and voila! A working loco. 

Not a chance. In the "good old days", etched kits were designed with a pen and paper. The parts would be drawn out several times the size they were required, and the photographically reduced to make the tools for the etching process. 

Sometimes, this didn't mean they were very accurate. This kit includes lovely pre-formed sides, which should drop into a half-etch line on the footplate. Everything held in place, and easy to assemble. 

Except they don't. The sides need to be fixed in place the thickness of the metal outside the etched line. 

Wish me luck...

Solebars and buffer beams on

 

Time for the gas torch to earn its keep. The larger lumps of brass are coming together, acting as too big a heat sink, for even my 45w iron to handle. 

The solebars are about 2mm shorter than the floor, so a line was marked 1mm from each end to aid positioning. A couple of small bulldog clips hold each solebar in place. Then some blobs of solder are applied with the electric iron.

Lashings of PowerFlow flux are sloshed on to the join and then the gas torch used to melt the solder, blowing it along the join - exactly as I hoped it would do. The gas gets the solder hot faster than the brass can draw away the heat, or at least I think it does. 

Buffer beams are added by resting them on a lolly stick and standing the floor on top. Again, a tack with solder allows me to check all is well before final soldering. 

 

Two hours soldering

 

Two hours soldering while watching The Great British Bakeoff (sort of watching, paying more attention to the brass than the cakes). 

• Nuts attached to the footplate, in the right place (took two goes for one of them)
• Bufferbeams made from two layers of brass, sweated together. 
• Solebars bent up, and the overlays fitted in the channel. 
• The whole lor cleaned up with Hob Brite. 

I wonder if all the overlays tell me a bit about the era this kit was designed in? Would a more modern production require me to bomp out the rivets/bolts with a press? I'd prefer that to sweating layers of brass together if I'm honest. I even considered leaving the solebar overlays off for the moment and fixing them with superglue once all the hot work was complete. 

Still, the gas torch did the job, and I enjoyed blowing solder along the edges of the solebars.

Chassis build

 

Despite being without a gas torch, I decided to have a crack at the chassis anyway. My 45w Antex iron is pretty powerful, and I hoped to at least tack it together so I could make good the joins later. 

The basic lump is a simple fold up job. Making sure the sides are at right angles to the top takes a little care, bu not much. Running solder along the fold line, as the instructions instruct, isn't a bad ideas, although once the motor supports are in, a fiddly job as they are a tight fit even with the etching cusp cleaned away, shouldn't really be required. 

My only complaint, is that the holes for the axle bearings are slightly oversize. To ensure a square result, the wheels and axles were fitted, and the bearings tacked in place. The result is a chassis that appears to sit flat. 

I'm still pondering the drive. My instinct now is to go for Delrin chain, which I'll need to order as I can't remember where I put the stuff I bought "just in case" years ago. There's some extra detail to add, and paint before then though, as getting the wheels off the axle is harder than I expected, so I only want to do it once.

Sentinel

 

"+ wheels and motor" - music to the model railway kitbuilders ears. Everything being in the box means no extra cost, or rooting around trying to complete the kit. Maybe said mechanical bits are rubbish, but it's a start. 

I really don't need a brass kit for a Y1/Y3 shunter. If I need an O gauge version, there is the excellent Dapol RTR model available for two and a bit times the price I paid for this collection of brass and whitemetal bit. 

But, a bit of me has been thinking some soldering would be nice. I don't often get to do this for work for a start, and I've always (!) enjoyed building locomotive kits. And yes, I have lots in the stash awaiting my attention, but the instructions make this look like a pretty simple build. 

Opening the box, it looks like all the bits are in there. Along with a reciept for £163!

I like the pre-formed body parts. Putting the bends in the corners isn't easy, as I seem to recall from building a Crownline kit many years ago. I seem to remember something about using a bit of tube around a bolt in each corner. No need for that here. 

The biggest issue I can see is the that model is single-axle drive. Should I try to do something about this? If so, buy an extra gearbox, or Delrin chain? I've not got a layout to run the model on, so as long as it moves for the moment, I'll be happy. 

Anyway, I hope I'll crack on with this and blog it for you next week. Don't hold your breath though, as there are always surprises...