Search found 88 matches

by davebradwell
Tue Nov 12, 2019 6:00 pm
Forum: Baseboards and Carpentry
Topic: Plywood disaster
Replies: 34
Views: 1921

Re: Plywood disaster

To pass by the original thread briefly, isn't it good practice to stack the wood for a job in the room it's to be used for a few days before starting? I'm no joiner but I seem to have this in my head from somewhere way back. Perhaps it was just a strategy my Father used to delay a job. If you're goi...
by davebradwell
Mon Nov 11, 2019 4:50 pm
Forum: Coaches and NPCS
Topic: Thompson BZ 6 wheel van
Replies: 7
Views: 829

Re: Thompson BZ 6 wheel van

I just copied the prototype on my BZ - sprung the axleboxes at the ends normally and used swing links to suspend the ends of the centre springs to give an almost friction-free slide using plain bearings made from 2/1mm tube. Centre spring positioned above floor to give reasonable length links. It ca...
by davebradwell
Sun Oct 27, 2019 12:59 pm
Forum: Vehicle dynamics and trackholding
Topic: Better Running
Replies: 16
Views: 1160

Re: Better Running

A very good question and logical responses which have already split between numbers of derailments and smoothness of ride - might there be a link between the two? What type of suspension do you fail most often, Jim? Suggest that you would need to push sufficient vehicles to compress the buffers a li...
by davebradwell
Sun Oct 27, 2019 12:44 pm
Forum: Product Information
Topic: Masokits
Replies: 6
Views: 720

Re: Masokits

Well he's still alive - I had a long chat with him at Scaleforum.

DaveB
by davebradwell
Sun Oct 13, 2019 9:42 am
Forum: Track and Turnouts
Topic: Buffer Stops
Replies: 7
Views: 674

Re: Buffer Stops

I suspect you're on a loser trying to put tight bends in drawn steel rail......unless you do it at red heat which could be fun. Depends on the steel, of course and I'll bow out there quickly and hope someone will take this over. Why not just use N/S as it will be painted all over? Wasn't there a Pro...
by davebradwell
Sun Oct 13, 2019 9:04 am
Forum: Steam Locomotives
Topic: P4 steam loco driving wheels centre outside boss
Replies: 24
Views: 1569

Re: P4 steam loco driving wheels centre outside boss

Yes, certainly on classes of my acquaintance, mainly ex-NE, wheels for inside and outside cyl engines were quite different. The crank webs inside the frames displaced the axleboxes outwards as locos grew larger and the backs of the wheels were usually recessed to accommodate them. This in turn pushe...
by davebradwell
Wed Oct 09, 2019 8:29 am
Forum: Steam Locomotives
Topic: P4 steam loco driving wheels centre outside boss
Replies: 24
Views: 1569

Re: P4 steam loco driving wheels centre outside boss

I dug out sample LNER Pacific wheel drgs, Dave, and was surprised to find the face perfectly flush with the tyre - I expected a tiny boss like you suggest. Perhaps on lesser classes? I noticed that the crankpins have a 1/2" thick base which compares to our 0.3 flange or washer here so with thic...
by davebradwell
Tue Oct 08, 2019 10:18 am
Forum: Starting in P4
Topic: Making a Start - The Peak District Midland / Monsal Dale pre 1903
Replies: 1049
Views: 137251

Re: Making a Start - The Peak District Midland / Monsal Dale pre 1903

I can't help with lubricants as we avoided them at work - there was a danger that any vapour could be detected by the instrument itself. I acquired a tube of MTS2000 graphited grease (direct equivalent not now available in sensible quantities) which is good for crankpins and motion and I have some m...
by davebradwell
Tue Oct 08, 2019 8:32 am
Forum: Starting in P4
Topic: Making a Start - The Peak District Midland / Monsal Dale pre 1903
Replies: 1049
Views: 137251

Re: Making a Start - The Peak District Midland / Monsal Dale pre 1903

You might end up putting the ends of the cradle - or bridge - inside the frames, especially if you've arranged the platform to sit on top of them for support. Neater, too. You don't want much slop in the slot but you can tweak that anytime. Is it worth tackling the ashpan to confirm motor hidden? Ta...
by davebradwell
Mon Oct 07, 2019 7:09 pm
Forum: Starting in P4
Topic: Making a Start - The Peak District Midland / Monsal Dale pre 1903
Replies: 1049
Views: 137251

Re: Making a Start - The Peak District Midland / Monsal Dale pre 1903

I'm confusing the issue by my own attempts to generalise and of course there are extremes where side effects creep in. The general principle being used is as shown in the sketch below and I introduced the concept of inclined tabs to tackle the question of how far away from the axle it is possible to...
by davebradwell
Mon Oct 07, 2019 11:53 am
Forum: Steam Locomotives
Topic: P4 steam loco driving wheels centre outside boss
Replies: 24
Views: 1569

Re: P4 steam loco driving wheels centre outside boss

Might I suggest a different approach, Julian and do a sketch, not to scale, with the dimensions on. Do a section, or plan, of one side - put in the centreline and the tyre outer face with a dimension (10.85ish). Work back the other way with cylinder centre distance from CL, width of crosshead on whe...
by davebradwell
Mon Oct 07, 2019 11:34 am
Forum: Starting in P4
Topic: Making a Start - The Peak District Midland / Monsal Dale pre 1903
Replies: 1049
Views: 137251

Re: Making a Start - The Peak District Midland / Monsal Dale pre 1903

Ah, I can't have read things properly as I thought you were driving the rear axle to give maximum space in boiler. I would suggest that your tab could be further from the axle (that is higher) as you've got the cantilever situation here - if it works, however just leave it alone - I've seen tabs as ...
by davebradwell
Sat Oct 05, 2019 8:08 pm
Forum: Starting in P4
Topic: Making a Start - The Peak District Midland / Monsal Dale pre 1903
Replies: 1049
Views: 137251

Re: Making a Start - The Peak District Midland / Monsal Dale pre 1903

You'll have to solder the bits of the gearbox frame together - once you're sure the angles are correct - or it will jump about. Just put a little tack of solder on one side until you are certain the fit is correct. As for a tab, why not take advantage of Allan Goodwillie's timely appearance and put ...
by davebradwell
Sat Oct 05, 2019 1:04 pm
Forum: Starting in P4
Topic: Making a Start - The Peak District Midland / Monsal Dale pre 1903
Replies: 1049
Views: 137251

Re: Making a Start - The Peak District Midland / Monsal Dale pre 1903

Yes, Tim, the springs are holding it all together and must do so against the force of the torque re-action. This isn't very large, however, especially with the overhanging motor helping the springs. I detect a hint of wariness but I feel it would be safe enough here as the spring force is contained ...
by davebradwell
Fri Oct 04, 2019 8:56 pm
Forum: Starting in P4
Topic: Making a Start - The Peak District Midland / Monsal Dale pre 1903
Replies: 1049
Views: 137251

Re: Making a Start - The Peak District Midland / Monsal Dale pre 1903

Returning briefly to gearbox restraints, I feel that I swept away the torque link rather unfairly and am including here a concept for a rattle-free design. Scangear018.jpg The pin-point axle serves as a staybar and can rock freely in the locating holes. Such a bar is traditionally called a pitman in...
by davebradwell
Thu Oct 03, 2019 6:06 pm
Forum: Starting in P4
Topic: Making a Start - The Peak District Midland / Monsal Dale pre 1903
Replies: 1049
Views: 137251

Re: Making a Start - The Peak District Midland / Monsal Dale pre 1903

I have settled on the above tab system for locating gearboxes as it ticks all the boxes and doesn't introduce any compromises. Frame and tab are rigid structures - this is one of the advantages. Yes, ideally the tab should be directly above the axle but I have used the system on many Roadrunner+ gea...
by davebradwell
Wed Oct 02, 2019 2:19 pm
Forum: Starting in P4
Topic: Making a Start - The Peak District Midland / Monsal Dale pre 1903
Replies: 1049
Views: 137251

Re: Making a Start - The Peak District Midland / Monsal Dale pre 1903

The motor and gearbox go up and down with the axle which passes through the rigid gearbox frame. The tab is a close fit in the slot but can slide (fit on tab can be adjusted with soldering iron) so gearbox goes up and down and can rotate sideways as springs require but cannot rock fore and aft about...
by davebradwell
Wed Oct 02, 2019 9:28 am
Forum: Starting in P4
Topic: Making a Start - The Peak District Midland / Monsal Dale pre 1903
Replies: 1049
Views: 137251

Re: Making a Start - The Peak District Midland / Monsal Dale pre 1903

While we're wading in here's the method I recommend for restraining the gearbox. The axle must be able to rock so the top of the motor will move sideways. The transverse slot is the obvious way of allowing this while taking the torque reaction. In practice I line the slot with slit ptfe tubing to av...
by davebradwell
Sat Sep 21, 2019 1:40 pm
Forum: Starting in P4
Topic: Making a Start - The Peak District Midland / Monsal Dale pre 1903
Replies: 1049
Views: 137251

Re: Making a Start - The Peak District Midland / Monsal Dale pre 1903

Did I see you were at Scaleforum Tim, if so it's easier for you to come over for a chat.

DaveB
by davebradwell
Sat Sep 21, 2019 8:57 am
Forum: Starting in P4
Topic: Making a Start - The Peak District Midland / Monsal Dale pre 1903
Replies: 1049
Views: 137251

Re: Making a Start - The Peak District Midland / Monsal Dale pre 1903

You're making a nice job of it and I noticed your attempts to introduce a bit of precision. Surely it deserves a cylinder front and rear - the rear is visible as a continuation of the smokebox and the front can be seen under the buffer beam. There's always a very prominent motion bracket to support ...
by davebradwell
Fri Sep 20, 2019 10:29 am
Forum: Guest Book
Topic: Extracting coach wheels from Hornby Gresley suburbans
Replies: 13
Views: 1008

Re: Extracting coach wheels from Hornby Gresley suburbans

It's the great depth of the cones that makes removing the wheels so brutal. Axles are standard. Once they're out it's easy to carve away some plastic and deepen the groove in the bottom that lets them back in. Even Bachmanns benefit from a little extra clearance for the wheel faces. Just go for it! ...
by davebradwell
Fri Sep 20, 2019 9:45 am
Forum: Guest Book
Topic: Extracting coach wheels from Hornby Gresley suburbans
Replies: 13
Views: 1008

Re: Extracting coach wheels from Hornby Gresley suburbans

Well, I got mine out but recall it took some force. I filed the groove a bit deeper before fitting new wheels.

DaveB
by davebradwell
Wed Sep 18, 2019 10:17 pm
Forum: Steam Locomotives
Topic: Crab Comet conversion
Replies: 291
Views: 43579

Re: Crab Comet conversion

I found a broadside photo and thought your combination lever about right - the bottom pin comes over the lower edge of the slidebar on front centre. There is no rule that places the expansion link pivot on the centreline of the valve but that does seem to be the case here and your GA should confirm ...
by davebradwell
Wed Sep 18, 2019 10:30 am
Forum: Steam Locomotives
Topic: Crab Comet conversion
Replies: 291
Views: 43579

Re: Crab Comet conversion

The wheel seat is 2.5 mm long at most and less if you file off the protruding front boss, as I do, on outside cylinder engines to allow the prototype valve gear alignment. This doesn't leave much space for even a single groove as you're relying on leaving some plastic to locate the wheel square to t...
by davebradwell
Sun Sep 15, 2019 5:05 pm
Forum: Steam Locomotives
Topic: Crab Comet conversion
Replies: 291
Views: 43579

Re: Crab Comet conversion

I could well award that an ok, Julian. Your shim washer saves it by spreading the force from the small diameter end of the tightened flangeless crankpin over a larger area so that it doesn't slowly sink into the plastic wheel boss with time and let the return crank loosen. A drop of shellac and it m...

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