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Speed flap versus Tommy timer

Posted: Wed Aug 08, 2018 11:57 am
by Braaainz
Working up my first Tommy timer rocket, but love the idea of a speed flap.

I noticed that most seem to prefer Tommy timers. Is this just because of ease of construction? Or are speed flap really unreliable?

Re: Speed flap versus Tommy timer

Posted: Wed Aug 08, 2018 2:19 pm
by anachronist
A speed flap will deploy your parachute when the rocket slows down sufficiently. It could still be going up, or be right at apogee. This is useful if you want to extend the parachuting time. There are contests for that, in fact there's a record here on WRA2 for longest duration flight.

Otherwise, if you aren't interested in maximizing parachuting time, a timer can be timed so that the parachute deploys on the way down. The lower you can deploy the chute, the less chance that the rocket will drift into a tree on the way down.

Re: Speed flap versus Tommy timer

Posted: Fri Aug 10, 2018 11:21 pm
by Terranoid Labs
I tried the flap system for my first real rocket and didn't like it because it seemed difficult to get it to deploy in a reliable way. I also had a gut feeling that there was a bunch of added drag, so I switched to Tomy timers. I had instant success on my first iteration, so that's the road I'm headed down at this point. That being said, the 2.0 version of the Tomy timer deployment is 1 for 4 this week, so I'm kind of sitting here scratching my head and questioning my decision making. I know for sure that one of those failures was operator error and another was from not learning a thing from the previous launch fail, so I still have faith in the Tomy.

Side note - I started out looking at my local thrift shops for wind ups and found many of them are either broken or low quality. In my area there is a Party City store that carries wind up toys called Z Wind Ups that have very nice timers in them and they seem to be very robust. They go for $3.99 a piece, so not exactly as inexpensive as the stuff you'll find on Amazon or Ebay, but I haven't broken one on a crash yet.

Re: Speed flap versus Tommy timer

Posted: Sat Aug 11, 2018 1:47 am
by anachronist
Terranoid Labs wrote: Fri Aug 10, 2018 11:21 pmIn my area there is a Party City store that carries wind up toys called Z Wind Ups that have very nice timers in them and they seem to be very robust. They go for $3.99 a piece, so not exactly as inexpensive as the stuff you'll find on Amazon or Ebay, but I haven't broken one on a crash yet.
$3.99 isn't expensive compared to a deployment altimeter and servo mechanism. I recall spending $50 on launcher parts alone.

Re: Speed flap versus Tommy timer

Posted: Sat Aug 11, 2018 5:12 pm
by Terranoid Labs
Ha, that is true. I'm trying to do this on the cheap, but it adds up pretty quick.

Re: Speed flap versus Tommy timer

Posted: Wed Aug 15, 2018 7:02 pm
by addstogether2
Hi I also had problems when I started using tommy timers.
I totalled my first one as I was setting the delay for too long.

The best way is to use the simulators and then work out where to set your timer position based on how long you require.

Then trial and error for the fine adjustment.

Al

Re: Speed flap versus Tommy timer

Posted: Sat Aug 18, 2018 1:18 pm
by retrotec29
I will second using a simulator as the first step in a successful tommy timer flight. I kill dinosaurs to.
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IMG_20180607_200220744_HDR_1534612450122_2.JPG (116.17 KiB) Viewed 32 times

Re: Speed flap versus Tommy timer

Posted: Sat Aug 18, 2018 5:50 pm
by addstogether2
Those Tommy timers look massive in the photo.

Re: Speed flap versus Tommy timer

Posted: Sun Aug 19, 2018 9:26 am
by retrotec29
A little bigger than most. The gearing resists the winding of the rubber band well.