Have made severa identical (as much as possible) bits.
View attachment 116443 But still can not decide how to deal with other end of the feedarms where LNB-holder (holders in case of multifeed) will be located.
Ok, now that you have set the ball in motion, here's another 5 cents of speculation:
Thinking about the concept, I believe it would be good to scope the project.
I would section a feed-arm concept into three different types:
- Single LNB, with room for adjustment to find the perfect spot for the LNB.
- Mlutiple LNB, using LNBs offset left and right to receive multiple sats on a fixed installation ("semi-multi-focus").
- Single LNB, with Cassegrain sub-reflector.
As you are working with refelctor attached feed-arms, we will disregard all the Rx/Tx configured feed-arm holder which have additional (steel) support for the feedarms (in order to avoid warping the dish when hanging several Kg of electronics at the other end of the feed arm).
The first type are for fixed installations, and only need to support the weight of a standard LNB, but in such a way that the positioning of the LNB can be changed up/down, in/out, and possibly even left/right. You have yourself made designs in the past with square feed-arms that would fall in this category. One possible focus point could be to make it very easy to angle and move the LNB when tuning the dish (think no-tools).
This type also work for motorised single LNB installations.
The second type is is for your fixed installations, but supporting reception from multiple sats at the same time. For this set-up, I would still propose to use the triangular feed-arm configuration, as this fits your bottom arm bracket concept better than a square tube that requires attachment to the rim of the dish. L-shaped steel bars would work very well, minimising the amount of customised material required. You can graft some attachment bar to the far ends supporting your very nice LNB holder for the T90s (or even the SMW OA-1600).
The third type requires and LNB arm that is lower than a "normal" arm, and supports the sub-reflector of some other dish manufacturer (Fibo, Visiosat), has plenty of room for an LNB hanging "down". For this arrangement, I would again promote the triangular feed-arm configuration, which could leave space enought for e.g. an Inverto Black Ultra fitted just before the sub-reflector between the two feed-arms.
There is potentially a fourth type, which caters for a motorised LNB changer - but this needs to incorporate changer mechanism in feed-arm assembly. And it will probably also require the feed-arm to be attached and support by something more sturdier than the bottom feed-arm attachment point on the dish surface. And thus mean danger of warping the dish. I will therefore leave this out of this category.
There is of course the fifth type, which is S-band-gizmo supporting feed-arms, but these are very rare and S-band has a nice Prodelin for this purpose.
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The beautiful thing would of course be if all three types of feed-arm configurations could be made with a modular approach, so that the components for all three types were more or less the same, with the same feed-arms, the same LNB holders, etc.etc. You could make a generic "pimp-up" kit, which could be used for any of the configurations... Now there's a design challenge!