Blastoff (FW) Build Diary

[Liftoff]

1. Motor inside the wheel:
Sure saves a lot of space (and some weight) but from what i have seen the wheels are amongst the most often damaged parts.
Putting something as valuable (well, depends on the motor, but i count all the machining need in here) to a place that likely to get hit sounds like a risky option. Might be worth it, if you can machine it yourself, and the motors aren't too expensive/if you are willing and able to have enough spares around.

Maybe it was not clear from the drawings - the wheels are totally encased by 10mm aluminium and 6mm titanium on the sides and 10mm HDPE on the top, so I'm thinking they will be pretty safe there - the only exposed part will be point of contact with the floor which is inevitable, I opted for motor inside wheel actually to protect the motor; being an outrunner I'd rather have it tucked away from anything loose which could end up a tangled mess.

2. Springs tend to loose a bit when keeping them under pressure.
Heavily depends on the kind of spring you use, and i doubt the effect would be noticeable in our short "active" periods. Just maybe something to keep in mind.

Yes I agree with you on this, I'm using die springs rated at 1000kg when compressed 25% of their length. At this 25% compression the travel is 38mm and I can get approx service life of 150000 cycles without the spring setting. All this info of course is from the spring manufacturer not myself!

3. Springs for the actual flip, and pneumatics to compress them again. Interesting Idea to design it that way round, but you'll need a lot of air to get those compressed (but you can do it a bit slower than the air is used normally, so less valve freezing).
Possible problem i see here: if anything in your pneumatics get damaged, you'll stay there with the flipper wide open, possibly showing all your inside vulnerable. Others might still work as wedge without their pneumatics, you won't.

As one spring is rated at 1000kg I figured a 51mm bore ram at 55bar will be capable of compressing the spring. The valve I plan to build is not a high flow valve and gas will flow through 1mm orifices. The QEV through which the gas flows to compress the ram has also a 1mm orifice. This should help prevent the pneumatics getting frozen, but only prototyping and testing can really determine the outcome.

As you correctly pointed out, my biggest concern is the flipper remaining open if the pneumatics malfunction. In actual fact the system is very simple, in that it comprises of a solenoid valve and a couple of QEV's, so if it's well designed and tested very little can go wrong.