Considering getting vacuum pump.

General Composites Discussions Equipment Talk
#1

Have already built one bamboo mountain bike and wrapped the joints with carbon tow to form the lugs. I used hi shrink tape for compression on the lugs. Worked okay but I’m pretty sure there’s a high resin to fiber ratio. After a year of riding none of the joints have failed so seems to be strong enough. For the next frame I want to try vacuum bagging but have a couple concerns.

There are 5 main joints on a traditional frame so that means I will be bagging the frame five times. So my question is when bagging, does the pump have to run constantly until the cf/epoxy cures on each joint before I can start the next joint? My first frame only took me about 6 hours from start to finish to wrap all the joints, this could take days if so. I’m only asking this because I don’t know, but when bagging, once you get enough air out, can you clamp off and cut the hose and move on to wrap the next joint and bag it? Does that even make sense?

Do you guys have any recommendations for a cheap small vacuum pump that works fairly well? The area of coverage for each joing will be less than 1 square foot.

Thanks.

#2

Well, in terms of processing, you can bag one section, vacuum it, move on to your next joint, bag it, clamp the hose on your first bag, manifold a tube to the next joint, pull vacuum, and let go of the clamp on the first one. Yes, you CAN disconnect fully, as long as you are 100% sure your bag is perfectly sealed. Quick Disconnects are great for that.
However, why do each joint separately if it only takes 6 hours? Get a long gel epoxy, or a low-heat cured one. Maybe do 2 joints at a time.
Either way, yes, clamping and moving on works. Make a manifold out of some tube and a few barb fittings with ball valves. Use as many, or few as needed without compromising the other lines.

#3


My bike is very similar to this one. The reason to bag each joint separately is 1) with the complexity of the three joints of the main triangle, it would be easier, 2) it would be a waste of unnecessary bagging material if I did the whole frame all at once and 3) by the time I finish my last joint, my other joints would be very tacky by then. Can you still bag and pull excess resin out when it’s tacky and has been curing for 4+ hours?

As far as epoxies go, too late to get a slow gel epoxy since I have already ordered West 105/205 which has only a 1 hour work time which is enough time to get each joint wrapped and bagged. I also don’t want to try a low heat curing epoxy because dry bamboo risks splitting when heating.

I know the Harbor Freight vacuum pumps are for ac systems, but do you think that would do okay for bagging less than 1 square feet?

#4

I bought an HF pump as backup pump and for small laminates it works fine. However it does spit a TON of oil if there’s any leak at all, I’ve sometimes had to put it outside when I let it run overnight.