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Truss vs Tube


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This is a question about RC scopes, but the same probably applies to Dobs but maybe this type of scope results in a different answer. Why use a truss?

Specifically, there are a range of 10"-14" RC scopes (the GSO models) which come in tube and truss versions, and the truss systems tend to be much higher in cost as well as a lot heavier than their tube counterparts. What advantage could a truss give in this situation to justify this, apart from the improved cooling ability and the fact they look cooler which to me seems a very high price to pay (pardon the pun) for just these 2 factors.

Cheers

Matt

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I am surprised that the truss versions are heavier. Trusses were originally needed for large telescopes where the weight of a tube would have been prohibitive and a much lighter truss design was needed. It is a long time since I was taught mechanics but I seem to remember that tubes are, weight for weight, the stiffest possible structures and that clever truss designs, notably the Serrurier type, overcome the lack of stiffness by having equal amounts of sag front and back, thus maintaining the primary and secondary mirrors in alignment. I would hazard a guess that for modest sized telescopes, the tube design is technically superior in terms of stiffness and maintaining alignment / collimation.Not so nice to look at though!

Regards, Hugh

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truss tubes are easier to manufacture by hand than lay up tubes from grp and carbon. you just need to calculate length and angles for the truss tubes and screw them down. If you want a serrurier, then there are some more interesting calculations to make about lengths and weights.

I know some people on here have made some very nice looking tubes from different lay-up methods. I think the problem that we get to in making truss tubes is that the central part has to be stiff and strong to carry the mounting plate which makes it heavy. A wide tube is very easy to be stiff whereas multiple narrow tubes have to be heavy walled or wider to get the same result.

Mike

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