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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Issues with fitting exhaust boxes due to thermal expansion and contraction on chassis engines.

Identifier  ExFiles\Box 38\4\  Scan037
Date  23th August 1921
  
X3436
FR
BY from EP{G. Eric Platford - Chief Quality Engineer}
c. to Hs.{Lord Ernest Hives - Chair}
c. to E.{Mr Elliott - Chief Engineer}
RECEIVED
EP{G. Eric Platford - Chief Quality Engineer}10/H23.8.21.

CHASSIS - re FITTING EXHAUST BOXES. X3436

We still continue to have trouble with the fitting of exhaust boxes on the chassis engines.

The trouble is that after the engine has been run, the exhaust boxes bind on the steady pin or on the base of the fixing studs.

Action was taken for the exhaust boxes to be fixed so that they were quite clear in this respect when new, but it appears that there is insufficient clearance allowed for expansion nor for contraction of these exhaust boxes, which takes place after they have been heated up on the engine.

This point I understand was brought to your attention some time ago, and it was suggested by you that the cause may be due to the clips being fixed too tight.

We have made quite sure that the clips themselves do not spigot the exhaust box in position.

We have made specific tests and measured the expansion and contraction of these boxes. Three were checked, and we find that the maximum expansion from centre to centre of the outer ports with the exhaust box heated to its maximum, i.e. 750° C, with the engine running on the unit test bed, it was as much as .15", whereas when cooled, the contraction from its original length had taken place to the extent of .071".

The amount of expansion and contraction varied on the three boxes. One of the boxes showed a brinnell test of 185. This gave a maximum expansion and minimum contraction. The other two boxes showed brinell of 121. These gave an expansion of .125" and contraction of .071".

I do not feel that this range will be actually achieved when the engine is in service, but I consider that allowance should be made in the manufacture and fitting of these parts, so that this amount of contraction and expansion can be attained, and the box still be clear on its fittings, which is not the case at present.

It was also found that if we filed away the flanges of the boxes so as to obtain this range, then we are in trouble when making the joint between the exhaust box and the cylinder, the joint face being locally cut away. From the tests it appears essential that some extra clearance should be given.

EP.{G. Eric Platford - Chief Quality Engineer}
  
  


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