Advice on building a chassis using Alan Gibson Mainframes

[hayfield]

I am hoping someone will give me the heads up on sequence of constructing a chassis using a set of Gibson mainframes along with their hornblocks, the chassis is for a Beattie Well Tank, I do have some 2mm hornblocks fot the front wheels

 

 

I have built both Rigid chassis from both Comet and Perseverance and compensated from Perseverance, but these had tab slots and a different system. I have never built  one from Milled frames

 

Its getting the frame square that concerns me, I have some London Road hornblock guides, I am guessing I fit the frame spacers first then the hornblock guides, I have a set of instructions for fitting the hornblocks but would appreciate to find out what others have found out works

 

Thanks

 

 

 

I will try and get a set of 7' coupling rods tomorrow

[JeffP]

Yes, fit frame spacers to one side, ensuring they are at right angles to the frame and parallel to the top of the frames. then place second side, hold with rubber bands, tack solder and solder up, again, ensuring right angles, so that the frames sit parallel to one another and vertical on a flat sufrace. I'd suggest 180 deg solder, then the hornblocks can be fitted using 145 deg.

Best luck.

 

Edited to say: if there aren't fixed places for frame spacers, check on a drawing that they won't foul motor, gearbox, pickups etc. I used to use the Perseverance type that folded up into an open ended shallow box, t5hew fitted them open end down.

Edited March 23, 2019 by JeffP
Added something

[Brassey]

The MJT hornblocks include an etch for a fixed axle which is a useful option anway.  I have soldered these in place first to ensure at least one axle is square while soldering up, usually the driven one.  This can be removed and the moving hornblocks then soldered in using the rods for alignment.   If you haven't got any MJT hornblocks I guess a bit of scrap with 1/8" holes would work.

 

A chassis jig is also helpful in this situation.

[sej]

Hi John,

You could buy turned spacers from various places (Comet possibly?), usually in packs of three, three is best! Work out where you want to put them where they won't get in the way of stuff as mentioned in previous posts. Either tack solder the frames together or use double-sided tape and line them up accurately. Drill some appropriate sized holes, separate the frames again, and then screw everything together. You can then either keep them as they are, or use them temporarily while you solder in other forms of frame spacer.

 

Cheers

Simon

[Nick Holliday]

The Alan Gibson frames usually come with a number of holes pre-formed, I think for their pickups and for brake gear. I am not sure of the sizes they come in, but it might cut out a couple of the stages that Simon has suggested. Comet do a set of temporary spacers, but they are designed to suit axle sizes, which may be a bit large, but the ones you used to be able to get from Studiolith and Exactoscale might work, or a suitable size of rod might do the trick.

[Izzy]

 

It's a while since I built a chassis using these parts, but this is what I remember.

 

The frames are quite soft, using engraving brass, so care in handling is needed, it's all too easy to twist/distort them out of alignment until they are soldered up with frame spacers. This is especially so above the hornblock cut-outs, but I see that these have quite a bit of frame above them. The spot holes are for brake hangers, and Gibson sprung pickups. Having used the latter I would say that simple wire scraper pickups are easier/better/more reliable, especially if you are building to one of the narrower (OO/EM) gauges where space is tighter anyway.

 

The Gibson hornblocks benefit from being assembled and checked before fitting into the frames to ensure they fold up correctly, fit the frames nicely, and there isn't too much slop in the bearings while moving easily up and down in them. The etched fold-up lines are quite wide, so you have to watch they fold up squarely and at the correct size. I always fitted the tapped washer/nuts before folding them up, again easier on the flat. And they are best soldered into place before you assemble the frames with spacers, while they are also flat.

 

If you have drilled holes for the brake hanger wire - 0.45mm -  you can fit a few lengths through and solder these into place as a temporary measure to assist with fitting whatever spacers you want. I used to just cut these from flat brass sheet or such as K&S strip. Depends on how thick you feel you need them, 10-15thou is often quite enough and from 5mm wide. easier than trying to drill holes all over the place, and they can be moved/altered as found neccesary. I would not suggest trying to make L shaped fold up ones, but use two separate pieces. A few flat ones at different angles works just as well. A couple for body attachment etc and the rest to keep things square. Obviously it's best if you plan out the chassis before starting working on it, and check the frames don't need altering in shape to fit the particular body you are using. IIRC Alan made most of them to suit what somebody had asked for, a particular RTR body maybe, or another makers etched kit.

 

Izzy

 

[Jol Wilkinson]

John,

 

Izzy has some good ideas and you will get plenty of differing advice, so here is my bit.

 

Use fold up etched "L" or "U" spacers, solder one to the front of one frame, the other to the rear of the other frame. Put the two frames together with straight wire through the existing holes  in the frames to check alignment and solder one spacer to the opposite frame and then the other. This the Iain Rice technique and seemingly minimises heat distortion (it's how I do all my etched frame builds). Add any additional spacers.

 

Fold up and assemble the etched hornguides, take care not to get any solder "fillets" that will stop the bearing from sliding freely. Fit one centrally and vertically by eye, then its opposite mate using a LRM alignment jig, checking by eye and with a square that it correctly aligned. Then proceed to fit the other hornguide/bearings as usual with the jigs and rods.

 

Jol

Edited March 25, 2019 by Jol Wilkinson
Additional text

[hayfield]

Sorry for the late reply, but been at Ally Pally all weekend. Thanks for all the super suggestions, I have visitors this week so time will be limited, plus I will try and get some sprung steel wire for use in lining up the holes

 

Now I know its build the chassis first then fit the horn blocks

 

A big thanks to all