Fitting circular windows on Large Boilered Tich ??? Best Options ???

Hi ..

Has anybody had experience of fitting the circular windows on the large boilered Tich at all?

The information in the "Tich Book" is non-existent ((

I have spent hours trying to figure out the best way to do this and not really getting anywhere.

Mike

Which particular aspect is causing you problems?

If it's cutting large-diameter holes in thin sheet-metal I'd look at using a step-drill or cone-drill of nearest to drawing size. (Step-drills advance in 1 or 0.5mm steps - since 'Tich' is a freelance design not a fine-scale replica, the portholes a mm over or under won't spoil the appearance.)

Or if you have a milling-machine and boring-head, hole-saw or step-drill the bulk out and bore to finished size. Be aware that a hole-saw is likely to cut a rather ragged hole above its nominal diameter.

The window trim is best turned and you could try super-gluing the blank to a thick disc of some suitable backing material to hold in the 4-jaw chuck or screwed to the face-plate. Be thorough with the gluing and take only light cuts. Use heat to break the bond afterwards.

If you use glass there are ways to cut discs from it, usually based on what is effectively a tubular lap. I have not tried it so can't vouch for its ease or efficacy

Acrylic or polycarbonate sheet "glazing" might be best made by using double-sided tape to stick a blank sawn circular but slightly over-size to a disc and trimmed to diameter on the lathe, as with the bezels. I'm not sure what the best solvent for un-sticking them and removing the residue without attacking the plastic might be, though. Soaking in warm soapy water? Or a kitchen cleanser? (Test on a scrap of the material first.)

I seem to remember these were advertised once, but can't remember where.

If it helps you can get clear acrylic discs in various thickness and a range of diameters from a well know site. I am guessing the window trim will be turned to captivate the window but should you need to glue it then R/C Modellers Canopy Glue is ideal.

Ron

• Cut the window spaces in the cab front - I would clamp to the drill table and use a tank cutter very slowly.
• Remove the centre drill from the tank cutter and use it to cut two disks of plastic (you may need to change the setting depending upon the shape of the cutter).
• Chuck a large piece of metal in the lathe and hollow out the end about half an inch or so to leave a thick walled tube large enough in diameter to allow for a ring of 8 or 10 or 12ba bolts to hold it to the cab front outside the round window, but with a bore that is a bit smaller to hold the plastic in place.
• Drill holes for bolts in the frame - I would use a tool post drill, but in the past I have made a guide that I have held in the tool post and used a hand held drill.
• Part off two slices and you have your frames. Drill holes in the cab front and bolt frames in place with plastic in between.
• I would probably face out the metal enough for 2 and a bit frames at a time before drilling deeper and facing/boring deeper for the second pair taking the size from the 'bit' still there after parting the first set off.

Hi Guys ... many thanks for your thoughts and suggestions.

I definitely want to avoid gluing in the circular brass frames but it proving to be a challenging job as I don't want the frames to look too large and the actual "glass/polycarbonate" being too small.

The options that I can see is using 10BA screws to bolt front & back frames in position ( glass being trapped between them ) .... or ... maybe a "swivel" type frame with top & bottom pivots.

I suspect this is going to take some time to sort out ... but keep my brain cells from dying!

Mike

Yes - trapping the glass between screwed-together bezels is a typical practice.

Putting the screws through the spectacle-plate too, helps keep the bezel width down. The outer ring could be of T-ring form, its very thin up-stand slightly less high than the plate thickness, to locate it concentrically and to hold the glass. Spot-drill the spectacle-plate from one of the drilled bezels, being careful not to widen the holes in the bezel.

I wouldn't add the complexity of opening windows, unless perhaps you are fitting a full cab. As I recall the Tich "cab" as designed is no more than a spectacle-plate plus a couple of low side-sheets.