Stuart 10V

[Bob Unitt 1Participant @bobunitt1]

I've got a 10H on my to-do list (1950's kit, my son found it when clearing out very dusty attic). Will this have a similar problem, or did it just affect the 10V ?

[JasonBModerator @jasonb]

As the OP's problem was a difference between the Stuart drawings and the 10V book I assume you won't be using the book so no problem.

[Bob Unitt 1Participant @bobunitt1]

Posted by JasonB on 12/09/2023 10:04:17:

As the OP's problem was a difference between the Stuart drawings and the 10V book I assume you won't be using the book so no problem.

True, for some reason I thought they shared the same book.

[JasonBModerator @jasonb]

Old drawings certainly have all the options on the same sheet, I've not actually got the book but think it only covers the vertical 10 V though most parts are the same between the two engines including space between bearings and the bearings themselves.

[Scott Murray 1Participant @scottmurray1]

Hi,

I am ready to start machining the eccentric strap for the Stuart 10V. Is there anything in particular I should be aware of/watch out for? For example I notice the arm of the strap is cast slightly off centre to the main bearing end that locates the eccentric sheave.

Scott.

[DjangoParticipant @django]

Just be aware that the “Gun Metal” is very malleable and easily distorted, so clamping methods are critical. A good portion of the work is hand work, so just take your time. The part is more delicate than it appears, but not overly challenging.

The 10H has the same part, just longer.  If you plan to add reversing, you might want to hold off on the eccentric strap since this one would not be used. 

Edited By Django on 21/09/2023 13:16:23

Edited By Django on 21/09/2023 13:22:23

Edited By Django on 21/09/2023 13:22:55

[JasonBModerator @jasonb]

Most Stuart eccentric starps were/are hot brass pressings, not sure of the very latest but they may well be part CNC machined brass the same as the current conrods are but not gun metal..

I'd try and layout the hole inline with the actual rod and see if there is enough material either side to get the clamping bolts in, you could even leave th ebolt out on the solid side as it is only decorative the one on th esplit side is what adjusts the fit.

[Neil AParticipant @neila]

I have just reached the stage of machining the crankshaft on an old set of 10V castings. This set has the old forged crankshaft and I believe that this is where the difference in the dimension over the crank webs has occurred.

The new fabricated crankshaft is supplied with bar for the webs that is 3/16″ thick. So the dimension over the webs is 3/16 + 3/16 + 5/16 = 11/16 as shown in the newer book.

The forged crankshaft measures a bare 11/16 over the webs before machining, after machining this will give a nominal 5/8 as shown in the old book and the Stuart drawing (which has obviously not be updated).

This will mean that on the fabricated crankshaft the 1/8 dimension of the main bearings will face the webs, whereas on the old fabrication it will be the 5/32 dimension. The position of the eccentric will need to be checked for alignment, but should not a problem as there is a 1/32 difference between the thickness of the valve chest on the old and new castings as shown on the old drawing and the new book.

After all these years there are still little traps there to catch you out. It’s a pity that the drawing was not amended to reflect the change to the crankshaft or even to highlight the the difference.

Neil

 

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