3mm or 1/8th inch – frame thickness

[Phil CatchesidesParticipant @philcatchesides15448]

Frames for Boxhill; not having the energy to saw out the frames I have bought some wonderfully accurate laser cut parts which are 3mm thick, the drawing shows 1/8th inch. Should I maintain the interior dimension or the exterior or split the difference ? Only 7 thou so no big deal – thoughts??

Phil

[Phil CatchesidesParticipant @philcatchesides15448]

[Bob Brown 1Participant @bobbrown1]

It is nearer 0.014" or almost 1/64" on the overall width, probably not enough to worry about externally and as the Boxhill has internal cylinders to save confusion I would maintain internal dimensions.

Bob

[Paul LousickParticipant @paullousick59116]

Hi Phil,

I am not familiar with the Boxhill but the choice of using the interior or exterior dimensions should depend on which is the best fit with the mating parts.

Paul.

[SteambuffParticipant @steambuff]

Hi,

I agree with Paul, it does not really matter.

One thing to be aware of when making the axles/fitting the wheels is the clearance between the side of the wheels and the frames. (You may need to adjust some of the dimensions on the axle to give the same clearance.

Dave

[Bob Brown 1Participant @bobbrown1]

Thinking about it IMHO it does matter as there are more parts fixed on the inside of the frame than the outside that also hold the two frames in position.

If you were attempting to work to an external dimensions then all the parts, buffer beams, stretchers, saddle and cylinders etc will be short or you will need to add 0.014" which is likely to get confusing. e.g. Cylinders are 4.250 wide so that dimension would need to be 4.264"

Bob

[julian atkinsParticipant @julianatkins58923]

hi phil,

as a builder of a 5"g terrier i would advise you to reduce the width of frame stays and cylinder block.

there is precious little room for the wheels to tilt with the 4.250" frame spacing, and such a wide spacing is totally unnecessary. alter the axleboxes accordingly and beware that the martin evans crank axle has excessive side play unless the axleboxes are not altered, plus the excessive eccentic throw causes problems in the valve gear department.

the buffer beams are also far too wide and deep when compared to fullsize.

cheers,

julian

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