Frame-storming (need help for the back bone)

I am I urgent need of a new Maslow frame (that answers the question in the old forum why I called it temporary {1 year}).

Roaming an island with no straight 2x4, no ply that does not look like a golf course, I came across aluminium profiles that look roughly like 2x4. The problem is that they are hollow, wall thickness of 1mm / ~0.0393 inch. The grade of the aluminium is likely lowest. I was told welding not possible. Bolt though is for 2 reasons not an option.

  1. It can deform the profile, even with big washers.
  2. I have screws sticking out where I don’t want them. No sinking screws in that stuff.

The price is interesting on low budget. Anything wood related is out of question with the humidity here and reaching beef jerky oven temperatures.

So, what I came up with and I have no idea if it will work:
I need 2 screws at minimum 2 cross connections, to avoid a pantograph. I decided to put 2 at each cross. The reason is, I plan to use 6mm ~/ 0.2362 screws and the hope lies in that number can add strength. A spoil board (hope to find hard foam) and a sheet plus skirting can add up in weight.

The connection profile, small hole at the joining and bigger outer holes for the tool:


Side view:

Front:

Forget the motor mounts, I will come up with an idea to make those solid. Will this frame be strucural stable wall hinged (6 hinges across)?

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@Gero I think your challenge is a good one as climates vary across the user group. Could you cap the extrusion and fill the internal of the extrusion with a fine material to create compression resistance? I think dry sand as an inert filler or even cement with rebar might work using the extrusion as a form? Holes are then drilled and filled with the plastic/nylon screw inserts. What do you think?

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Thank you @Borderline for the reply. You have given me a great idea to try something in the line of this: I’ve been investigating: https://www.youtube.com/watch?v=kawsFsFi6Pg
Expanding foam could also increase strength, but would not allow me to sink screws. The air-crete would allow that.
That’s why you post here, because this amazing community will guide the path. Still hoping the numbers just add up. If I get close to a good strength with my design, a filling could easily add the few more % to make it rock solid. Thank you!

@Gero Keep me updated as am interested if this might work and how much it weighs!!

Tip 1: drill the hole in the extrusion with a regular twist bit, then block the holes with duct tape, then pour the filler.

A masonry bit will be required to drill into the ‘crete’ otherwise you risk blunting you twist bit. I am concerned that aircrete might not have the required bond and crack when screws are inserted. you might consider these as potential fasteners. Definitely take the time to do a smaller proof in concept first! Concrete is permanent and with a very fine pebble (aquarium rock size) should be ideal.

What about a resin fill? Make a I beam mold from two part foam then resin fill it sort of like making a surf board.

Thank you

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You say there are no straight 2 x 4s i assume that means there is some lumber available so if you have a table saw you could mill down some pieces (short enough that warping isn’t a factor)so they could slide into your aluminum extrusions and they would be your hard points, then if you still wanted to you could drill some holes between hardpoints and fill with cement, foam, etc.

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once you fill the extrusions, you can then use through bolts.

I think your frame is probably overkill

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@dlang - Gero tore his motor off the mount during the calibration process running the “New Motor Shield” with a 10 amp power supply - I consider him a super user. He needs more beefy components.

Thank you

Super user or super stupid? The ‘pull chain tight’ is not recommended with this setup.
Here is a picture a crack in the motor housing a piece of tape :man_facepalming: of the left motor.


I dumped the idea of the hollow tube frame as I don’t trust the 1mm aluminium any more.
Currently I am modifying my old frame with a beefy overkill in antiflex and stiffness.

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was the motor attached to the bracket on the front or the back?

To the back, the inside of the bracket. The crack of the housing (tape leftover) extends to the lid.
image

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Would you say that it might not have cracked if the bracket had been attached to the front, sprocket side?

That was my thinking, reduce the leverage as much as possible

now you have me thinking fold in gussets on our design - I do have a spot welder somewhere.

Isn’t that how I mounted it? I would expect the bracket to take the main force mounted this way.

My apologies! There is no crack in the motor housing. I feel really stupid now, being fooled twice by a piece of tape :man_facepalming:
On the third inspection right now the tape leftover was discovered. What a cheeky tape to start and end at the centre points of the motor mount threads. Sorry for the inconvenience caused.
Am I getting too paranoid with the forces involved? I think no. However, soon I will do a ‘pull chain tight’ again with a so overkilled frame and motor mount that we will find out what breaks after this 2 are ruled out.

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Whew! That’s good news! You had us all worried…:+1:

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I was quite convincing, wasn’t I :rofl:
Sorry again, was not intentional.

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Ok, I’ve lost my reputation reporting fake news. I need to get my reputation back.
So in exchange for something that was reported and did not break, I feel the need to present something that did.

You may laugh if you wish. It will not harm my ego.

The serious break something frame:
The 2x4’s were remounted to (on a lucky day) even out twists and bends.
A skirting of 21mm cplex was added beyond the outer 2 of 4 door hinges.
85x85mm ex table legs mounted across.
Levelled with the old tube and water trick and confirmed with 3 levellers.
I looked at the parts from the old mounts and recycled 2 of 3 parts on each side.
Just hoping for some time to put it all back together :grimacing:


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That looks plenty strong. How wide apart will the motors be?

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