1.1/2″ Allchin

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1.1/2″ Allchin

This topic has 6 replies, 5 voices, and was last updated 31 March 2015 at 10:37 by Dave Halford.

Viewing 7 posts - 1 through 7 (of 7 total)

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31 August 2009 at 09:14 #43216
michael bird
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@michaelbird72946
Hi,

I am thinking to build the 1.1/2″ Allchin Royal Chester. I acquired a set of castings, drawings and the book on Ebay. I am at the stage of reading the book and the plans.

Can I ask someone who knows if there are any mistakes on these drawings that I should know about before I start the build? I have found that they show the second shaft with a dia. over the splines as 17/32″ and the main shaft as 7/16″. It then shows the right hand spigot for the brake drum turned down to also 7/16″ whilst the drawing for the brake drum shows the bore at 1/2″ dia. and the second shaft bearings are shown as 7/16″. I assume that this can be jiggled by reducing the bore in the brake drum, but other drawing mistakes, if any, could be a problem if not spotted before, rather than after machining.

I am a late onset Tyro so if I am reading these drawings wrongly, please be understanding.

Michael Bird.
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31 August 2009 at 09:14 #2670
michael bird
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@michaelbird72946
Royal Chester
31 August 2009 at 19:51 #43222
mgj
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@mgj
I wonder if you aren’t making the same mistake that I did when I kicked off with my first TE – getting mesmerised by the drawings.

Obviously everything in a sub assembly has to fit, together, but up to a point, if you use a bit of 1/2″ steel for part x, and the drawing says 9/16, it probably is not going to matter too much unless appearance and strength are greatly affected. And most drawings make no mention of tolerances or clearances!

So if as I did (and the Little Samson drawings are very good), you misread the hornplate fittings and omit a 3/8″ dimension – well Ok the crankshaft is 3/8 too far forwards on the model – so the cylinder assy will be moved forwards 3/8 inch, and the blastpipe will be 3/8 shorter, as will the LOA.

This is a tragedy I shall just have to live with, and while I do so I shall reflect on the fact that these things were assembled by blacksmiths, and the dimensions of the originals varied too. And on the fact that my LS is sitting on all 4 wheels, that everything goes round where it should, without binding (all home cut gears and blanks) , running in (apart from the cast gears in the compensating centre), or other fiddling.

So its going to work – soon.

With all due deference to the purists. If you have a 1/2″ shaft, right or wrong, then you will know you need to make a 1/2″ hole in whatever fits. Spacing of gears and things like piston/con rod lengths and crank throw are bit more critical, but if you have one bit, in the main you make the other to fit!

Thats not to say that getting it dead right isn’t best (Even allowing for those occasions where is says fix dimension from model!). Of course.

(Next is a 4″ Foster!!)

Edited By meyrick griffith-jones on 31/08/2009 19:56:06
31 August 2009 at 20:09 #43223
JasonB
Moderator
@jasonb
If you read the text where it describes the spline cutting then the spigot at the end of the shaft should be 3/8 so it would seem that the bore for the brake drum is not 7/16.

But then again the sentence before gives the shaft at 9/16″ dia

Jason

Edited By JasonB on 31/08/2009 20:09:40
31 August 2009 at 21:02 #43224
mgj
Participant
@mgj
What do they say – for the guidance of the wise and blind obedience of fools!!
30 March 2015 at 15:37 #184968
Gustavo Andreoni
Participant
@gustavoandreoni29605
Hi everyone!

I have one kit to sell:

Allchin Royal Chester Model full Set

Thanks!
31 March 2015 at 10:37 #185045
Dave Halford
Participant
@davehalford22513
It's fair to say that you can't make all the parts to drawing and then assemble at the end like a pre machined kit.

These drawing were done to meet magazine deadlines, pre PC, drawn on paper and thats it. Errors were sometimes corrected in the magazine and sometimes errors crept in.

In other words, it was all a bit rushed and too hard to fix later.

Everything will need checking
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