Stevesopwith's S7 Workbench

adrian

Flying Squad
Rob. On the Sentinel Loco 7109 site there is a side view drawing of the double-ended version.

I'll try the 'address'. It's:

http://sentinel7109.blogspot.co.uk/search/label/Other Sentinel Locos
Sorry I missed this thread, been off the grid for a couple of weeks.

Agreed a really interesting and informative site, the owner is most amenable to a questions as well. I contacted him about the Y10 drawing he had to see if he had a drawing number for the Sentinel Archives and he sent me a high resolution image, apparently scanned from 1920/30s Sentinel catalogues. It's 1.6Mb (7,000x4300 jpg)

If you want to download it then I've stuck it on dropbox, hopefully permissions are set so you can see it.
 

Stevesopwith

Western Thunderer
The Avon Valley Railway staff have also been very helpful; most welcoming in response to my request to visit to survey the Fry.

Here's the latest progress: the gearbox and motor mount.

The gearbox is a Romford based 80:1 from Branchlines. I've modified it slightly by separating one side from the fold-up, and re-attaching it with 12 BA screws and tube spacers. This means that clearances between the bushes and gear faces can be optimised, leading to a very smooth running box.

The mounting has to have a degree of flex to suit the suspension. This is acheived by sandwiching the frame bracket between two squares of 1.5mm foam rubber over a slack fitting tube and stud. The little tags just help to keep things in line.

On final assembly, all the fixings can be left slightly slack while the running motor finds it's own position. Then everything can be tightened up.

Sentinel Motor Mount 1.jpg
 

Dog Star

Western Thunderer
Hi Steve,
There are some neat ideas coming from your direction.... I wonder how much is due to Sopwith? In the photo of the motor and frame plate there looks to be more to the motor mount than a couple of pieces of foam. When convenient, how about an "exploded view" of the parts?

thanks and regards, Graham
 

Stevesopwith

Western Thunderer
Here you go.....

From the left:

Split brass tube, clamping bracket and captive nut at the top, base of 1/16th brass to reinforce the 10 BA CS screw, with a compression limiting tube. This fits through the first foam pad, into the bracket. (from below as we look at it )... followed by the next pad..... the square washer plate and the nut and washer. The captive screw on the bracket then bolts to the loco frame.

I rarely get accused of under engineering. :)


Sentinel Motor Mount b.jpg
 

Dog Star

Western Thunderer
I shall pinch this idea, often :thumbs: .

The mounting plate in the centre of the previous photo.... one bolt or two affendi for securing to the frame?

Thank you, Graham
 

Stevesopwith

Western Thunderer
One gives sufficiently positive fixing, while allowing rotational adjustment to the optimal postion relative to the axle, before being tightened. Because the clamp spigot is a slack fit in the bracket, the motor restraint comes from the sponge, so there's never any direct force on the bolt. Anyway the movement from the suspension is tiny.

Glad you like it.
 

mickoo

Western Thunderer
The kit has a rigid, fold-up chassis which is perfectly useable, especially if fitted with some form of compensation.
However, although the full size loco doesn't have any inside frames, I wanted to try 'proper' S7 width frames and sprung hornblocks, partly as preparation for the Wantage steam locos.
Also, while I have a general design idea, the details will evolve as work proceeds; and that's much easier if the frames are separate units till final assembly.

So... two frame blanks were soldered together and the outline and axle hole positions marked. At each end a further hole was added on the axle line.
Once clamped to a piece of 12 mm ply, the whole unit was clamped to the drill table, using a 4 mm pin point axle to locate in the hole marker of one of the end holes. Using successive drill sizes, this hole was opened up to 2 mm. With the ply still clamped, the metal was removed, and it's hole gently broached to a snug clearance fit on 2 mm steel rod. ( more 4 mm axle. ) Using the drill as a press another 2 mm rod was pushed into the ply, and the metal replaced over it. This process was repeated for the remaining three holes, the two axles opened to 1/8", the last to 2 mm.

I now have a jig that will locate the axleboxes relative to the frames once I have cut out the outline and hornguide slots.


View attachment 13110
Steve what pillar drill is that please? I'm looking at getting one for S7 modelling so looking for feedback on whats good or bad. Nice work BTW and like the idea of the sacrificial ply and clamping method.

Kindest
 

Steph Dale

Western Thunderer
Steve what pillar drill is that please? I'm looking at getting one for S7 modelling so looking for feedback on whats good or bad. Nice work BTW and like the idea of the sacrificial ply and clamping method.

Kindest

Mick,

I've got the Proxxon TBM 220 and can say it's far surpassed my expectations. Stick with the colletts if you can, but even the (Rohm-made) conventional chuck is very good.

Steph
 

Stevesopwith

Western Thunderer
Mick... the drill is a Manix MD1, bought from Rejon Tools...... about £220..... on the recommendation of the proprieter. I have no experience of other similar range bench drills, having used my aging Unimat SL until reaching the conclusion it wasn't sufficiently accurate any more.

The Manix's 3 jaw chuck will take a 0.4 mm. normal shank drill, with no visible runout, and I recently drilled 300+ 0.5 mm. fishplate holes in N/S rail web, using only one large shank 0.5 mm. drill from Expo.

It's very quiet, the travel is light but positive, I use one finger to pull the lever, and you get good feedback, allowing precise regulation of the pressure. I think it's well worth taking time to devise suitable clamps, even if they only get used for one job.

Note to Moderator: Although this is all S7, it's not really S7 Group material; might this thread be moved to Area 51? I've got a Fry progress report pending.

Steve.
 

Stevesopwith

Western Thunderer
No Mick, I didn't mean you..... I think I should have started the whole Fry S7 Workbench thing in Area 51.

What do the Moderators think?

Steve.
 

Stevesopwith

Western Thunderer
I can hardly believe that my last post on this little monkey was late August. :oops:

I kept thinking... just one more bit and then I'll post.....only there were lots of bits!

The completed frame sides were assembled on a simple block jig to ensure right-angles.

The Hi-Level CSB Axle-boxes work very well.... After trials I settled on 017" spring wire, for a projected all-up weight of about 250gms.
The Delrin sprockets were modified by drilling to accept 1/8" bore axle bushes, one of which was soldered to a Brachlines 1/8" grub- screwed boss...... making positioning easier.
The slack in the chain is taken up by a simple 'slipper' device, ( an idea taken from '50s motor-cycle primary chaincase design. ) It is adjusted by the simple expedient of a few extra spacer washers.
In practice I found it better to remove the lower foam pad and washer from the motor mount. The motor leads hold everything in place perfectly satisfactorily.
The pick-ups are made of 2mm x .005" phosphor bronze. I originally fitted wires bearing on the treads... it worked, but there was a gradual build-up of grot from the N/S rail; and so far the new versions have worked perfectly. They'll be hidden by the outside frames.
I've completed the detailing of the gear covers, and most of the lower boiler and ash-pan, which is currently only pushed in place.. ( which is why it's crooked! ) The boiler space will eventually house a 'stay-live' capacitor to keep the motor running over less than perfectly clean spots.



Frys Sentinel Chassis 3.jpg



Frys Sentinel Chassis 2.jpg
 

mickoo

Western Thunderer
Very neat and tidy work, do you by chance have a photo that shows the top of the axle-boxes and CSB arrangement, I'm going to show my ignorance here and ask what CSB means, I'm guessing some sort of spring beam?

Kindest
 

Stevesopwith

Western Thunderer
Thanks Mick,
CSB stands for ' Continous Springy Beam'; and although I don't have a photo, you'll find all about them at www.highlevelkits.co.uk ... click on 'gearboxes'.
It's actually a very simple concept which, with a bit of simple scratch-building or etching, could easily be applied to 3/16" axle bearings for larger locos.

Cheers.... Steve.
 
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