timothy thompson

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i am working on tf b-25 and wish to actuate my bomb bay with air cylinders. I know you guys use them for gear doors all the time. the 25 is 1/9 scale. What type would you guys use

Stratotanker

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I use a lot of BVM cylinders, Ultra Precision has a good stuff too. Let me know if you need any more assistance.

Chris

timothy thompson

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they need to be small diameter and the problem is i am not sure of piston stroke and have no way to adjust these like i do with a clevis. unless im missing some info on these small cylinders

KC36330

TamJet is another good source for the cylinders. on the stroke you can either do some massive trig calculations or just install the hinges and measure the stroke required and add a mm or two so it has some extra pull on the door when fully closed.

timothy thompson

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can i add a clevis or ball link for adjustment

timothy thompson

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tamjet has good stuff will they take mastercard over the phone or paypal

KC36330

yes, and yes.

Stratotanker

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A lot of door hinging is trial and error believe it or not. If you use Tamjets style offset hinges you can use the short BVM cylinders and attach them to the horn and be close. I designed a custom horn that allowed me to utilze the long BVM cylinders on my Phoenix gear doors. I am pretty sure that this set up is what you are looking for. I will shoot you some pics, if it is what you are looking for, I will laser cut you some mounts and mail them to you.

Chris

Stratotanker

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Here is what I am talking about. You can play with the cylinder body position to tweak how far the doors open. Let me know if you need more help, I have LOTS of experience hinging doors and would be more than happy to help you out. I have a soft spot for the B-25!!!

Chris

Gordon Mc

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If the stock units from BVM, Tamjets or other RC sources don't work for you, look at the industrial stuff form e.g. Clippard : http://www.clippard.com/cylinders/Default.asp - I've use the minimatic cylinders a couple of times.

timothy thompson

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thanks guys strato im using nelson hinges and they work perfectly at hinging a b-25 bay. ill post pics here. Wow i was told not to ask here cause jet guys wont be of much help im glad I didnt listen!!! thank you guys

Kevin_W

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You can also mount the air cylinders at 90 degrees and use bellcranks, then you can adjust the final stroke by moving the clevises on either side of the bellcrank. This is what I did on the main gear doors of the Gripen I am building right now. I can post some pics later today (when the clear is dry enough that I can re-assemble it) to show how it works.

Or, if the stoke of the air cylinder is too long you can put a wheel collar on the shaft to use as a stop. I don't like doing this though because the air cylinder will never be able to be used for any future applications if it requires more stroke than you have limited it to.

timothy thompson

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heres what i have please post your pics! the hole in the middle of the bay is where my lipos go 7s each side! it has a complete bomb bay. the area with all the scale wiring up front is completly accesable from the other side. any pics or diagrams and sizes of cylinders would be appreciated

timothy thompson

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the wheel collar idea would not allow full travel and damage the cylinder correct?

Stratotanker

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I machine spacers that float on the cylinder shaft and limit travel to the desierd dimension. When you choose a cylinder and figure out if you need spacers, I can whip some out for you if you do not have access to a lathe. Would only take about twenty minutes for a basic spacer.

Chris

timothy thompson

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no lathe. ive been building and flying for 25 years but never used small cylinders for bomb bay or door operation till now. ill give you the measurements and you can tell me the kind of small cylinder i need .


pics of installation would be helpful too

timothy thompson

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strato you in the af? my daughter and son in law are at ft polk 1/509th airborne bravo co.

Stratotanker

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Yes I am, I work on KC-135s at Fairchild. Here is a picture of me doind some retract maintenace on my last deployment.

Chris

Stratotanker

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as far as the cylinder spacers go, you can use lengths of brass or copper tubing. I would go with the long BVM cylinders if I were you, it will give you a little more wiggle room in your install and will save a lot of headaches!!!

Chris

timothy thompson

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oh come on what a dream job! how about a tour if i come out there! i always travel to see my daughter. Do you get to fly in them working on the feft main! dual double tandem setup. im envious

Stratotanker

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I get lots of flight time in them. I even have simulator time, I get to fly around when I get tired of engine run practice. Lots of FUN!!!! You come up to Spokane and I will show you a jet!

Chris

timothy thompson

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you got it do you have any actual flight time. i will come out this summer ill pm my addy to you

Kevin_W

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Here are a couple of pics of the air cylinder on the right main gear door of my Gripen.
The cylinder had more travel than needed, so I adjusted the throw with the bellcrank.

timothy thompson

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interesting idea! how fast do your jets fly? Are there any that fly under or at 80mph. i always wanted a pcm L1011 but hes not in buisiness. Im 47 and cant keep up with 150mph airplanes. tried it once on a F-86 i slowed her down to where i could handle her and the landed! My bud showed me the high end performance and there is no way i could keep up with it. Looked like a streak!

Kevin_W

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Pretty much all jets will fly under 80mph, it's just not that much fun going that slow.