Torque on front engine stay

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

As we are building a frame for a 250 two stroke a question appeared regarding the front engine bracket. (torque support)

Here we have the front engine bracket. (engine is hanging in the frame)

Torque on front engine stay .engine-bracket1rkoj

And the rear engine stay:

Torque on front engine stay P1040497vak22

When the engine is producing torque to get the bike forward, will the engine push the front engine stay upwards towards the frame or will it pull the engine stay downwards?

Worded different: is the front engine stay (torque support) stressed with compressive or tensile load?
Best regards,

Bernd

If you have only one rear point support ( casing/ frame) the front support tend to contain the reciprocating torque given by the chain pignon : normaly compressive load. Whith 2 rear support points ( classic design) , the front support is practicaly free of loads.
Other: tensile or compressive limits are about the same in such materials, where is the problem?
Dan

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

Thanks for your answer, Dan.

The engine is fixed with two rear supports. 4x M8 fasteners, thread in aluminium. Not very massive, as the chassis is build for very low weight. (6kg frame, 3kg swingarm)

Please, se here.

The front engine stay itself will surely take high compressive and tensile loads.
There are doubts if the aluminium threads in the cylinder (4xM7) and in the crankcase (8xM8) would be abled to bear a high tensile load.
When the load on the front support is compressive (as you wrote) it would strain the threads less and spread over the flange surfaces of the components.
So are my thoughts.

And so it´s important for me if the load is compressive or tensile.

Best regards,
Bernd

Döllinger a écrit:: .... it´s important for me if the load is compressive or tensile.

Rest assured Bernd, it will be compressive, like Dan said.

If the loads will be tensile they don't increase the loads in threads when they are in under values of the treading tension of screw tightening.
Dan

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

Hallo Dan, hello Frits,

thank you very much for your answers. This information is calming me down.
The bike is nearly finished now, but i got something like a "bad conscience" after after a few people,
which are partly working with these engines in superkart doubted that the engine would stay in place under load.
Best regards,

Bernd

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