Are the fittings aluminum? I'm not familiar with the fittings you are going to use. I also don't know why commercial fittings are given the pressure ratings that they have. With PVC it's obvious, but if galvanized iron says 150psi then that seems strange to me but I'm sure there's some reason. Mayb...

Does anyone know if MrCrowley is still active on this forum? I have some questions regarding the constuction of his cannon and it appears the majority of the links to his Mjöllnir cannon are dead. Currently I'm having concerns with the fittings that I can get in the UK. Its turns out that the fittin...

A threaded boss at the rear can increase or reduce preload on the spring within a certain range, although this will also reduce spring travel. I did think about some adjustment to preload the spring, but I'm not sure I can find a suitable spring that would cover 1x to 10x mixes whilst also not redu...

Thanks Moonbogg That does give me confidence that I'm on the right track. I will double-check all the areas that the pressure will act on. I also had an idea the other day about using a spring to keep the piston sealed. Has anyone done this? spring concept.png Early concept, if this is a viable opti...

Something else I'd like someone's opinion on is the faces the chamber pressure and pilot pressure will be acting on Apologies for the metric units but currently I have the following: Chamber side of piston (235.62mm2): Chamber_face_area.png Pilot side of piston (2019.46mm2): Pilot_face_area.png I ha...

Thanks for the welcome back. So here is where I am at the moment. As recommended many moons ago I have added a large washer to secure the rubber face seal to the front of the piston. As before this is attached with an M10 screw. Pressed into the rubber face seal is a sleeve to allow the screw to cla...

Just to update anyone that is interested... This project is not dead, but life took over and 2 years passed. I had some issue with the 3D and lost my latest revisions, so will have to revisit the design. After re-reading this entire thread again I have some changes I'd like to make. I will post any ...

Thanks Moonbogg. Updates to the following: - Bumper OD reduced. There is now radial clearance of 1.5mm (Annoyingly, I didn't mean to completely fill the gap!) - Thickness of front seal increased form 8mm to 15mm (I'll need to find something suitable to make this from) - Screw securing front seal has...

Thanks for your answer’s guys. Some people don't mind working on the edge of the material specifications and operate on the assumption that something will probably give, while others won't touch anything without a 3 or 4 times safety margin. I can see the appeal, from a weight perspective, in gettin...

So, as I'm trying to get the piston assembly weight down to as little as possible, I've started to (try to) analyse the part in SolidWorks. My company used to use SolidWorks before moving to Catia, so I only have access to a basic version - meaning SimulationXpress is all I can run. I HAVE NEVER PER...

There's something about the orientation of the piston that isn't sitting right with me. I feel that having a design where the piston moves vertically, essentially sealing the chamber rather than the barrel would be better. As a picture is worth a 1000 words, here we go: Cannon_alternative.jpg What'...

Also, I think I'm going to change the tee used in my design to swept tee as shown below:
Thoughts?

There's something about the orientation of the piston that isn't sitting right with me. I feel that having a design where the piston moves vertically, essentially sealing the chamber rather than the barrel would be better. As a picture is worth a 1000 words, here we go: Cannon_alternative.jpg What's...

mrfoo wrote:Depending on dimensions, I might be able to sort you a block of teflon or two, for the cost of postage from cheese-eating surrender-monkey land. Drop me a PM if you're interested.

Thank you. Once I've finalised the piston design, I'll send you some dimensions and we'll sort something out.

The next issue I see is the bumper. I assume that little rubber washer in the back of the pilot is a bumper? Or is that used as a guide for the rod? It looks like a bumper. Correct, it is a bumper. I'm not exactly sure of the hardness but you're right, it does look woefully inadequate when consider...