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marks

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  1. If you want little itty bitty ramps. You can get builders wedges at a hardware store. The ones i have start at 6mm and go to about 25mm high. Youd have to stack them togetehr or screw a bit of plastic or metal sheet to it to widen it enough but they wouldnt scare your minis. You may wanna add a brace to your shocktowers too to protect them. Mine split after a trip to an offroad track. Was only doing little (30cm) jumps as well.
  2. I can redesign the arms if you want. Do you have a link to the files? I've done a few printed parts for my RC's and you are right in that you want to make the design based on the process. A molded part and a printed part have pretty much opposite requirements. Moldings can't be too thick otherwise they have issues with sinkmarks and voids. This is why the lunchbox arm is the shape it is. A printed part however doesnt have that restriction but it weaker than molding and along the layers its much weaker so a better approach would be to make it more monocoque looking (like a manta ray Arm) But with really big beefed up areas around the pivots. I have dome some arms like this before on my F1 car (3Racing FGX) and they worked very well, but that lent itself to printing vertically as it didnt have the integrated hingpin. If you had it printed front to back you would have broken in those areas, you would have definitely broken it at the hingepoints. If the printer can print in PETG that might solve the issue enough for you with this current design. PETG has much stronger interlayer bonding. Anyhoo Attached is a piccy of the FGX arms and also the camber link mount (wanted a shorter upper link for better camber gain) The arms are printed front to back but the link is printed top to bottom and you can see how much more chunky it is compares to the molded parts around it. It was pretty durable though.
  3. I do a fair bit of injection molded part design and the answer is a little complicated. In general if you are breaking a part in a certain area adding more material will help. If you are adding a material that is different from the original the stresses will be distributed between the 2 based on the stiffness of the 2. The higher stiffness material carries more stress. So wrapping a hinge point which breaks with carbon fiber will make it much less susceptible to cracking as the carbon is much stiffer than the ABS (or nylon) and so it carried the load more. This is why adding a metal or carbon brace to the front of a central hinge pin block essentially stops the block from breaking as it is now carrying the load. If you just randomly fill areas with something like epoxy (which is pretty stiff relative to abs and nylon) then the epoxy will carry most of the load through those areas, but if those areas weren't a weak part more load will be transferred to the other parts of the part which may fail more easily as the overall loads are higher. Basically more flexible parts have lower peak loads as there's more distance to dissipate the impact forces. Which is why sometimes aluminium arms and hubs may break the hinge points in the chassis more easily as they are very stiff and the peak forces they transfer are higher. In regards to molding. When a part is designed its not good to have really thick sections or thick and thin sections transitioning. So a designer will use ribs to try and stiffen the part. Depending on how the rib is used it could actually weaken the part even though its stiffer. If the rib is on the compression side the part will be generally stronger whereas if the rib is on the tension side it may weaken the part. If you can upload some pics of the part I can give you a bit more info based on that particular part. As it is this post is a super long one for a first post
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