Webbit example build: IC Power Installation

[David Davis]

Well done Ian!

 

I wish I could fly that well.

 

BEB's list of Webbit builders is on page 21 of the Charity Mass Build Chat Thread which was posted on 22nd February. According to that list, you are Webbiteer No 19.

 

 

Sad I know...

 

 

 

 

Edited By Biggles' Elder Brother - Moderator on 22/04/2011 15:01:57

[Doug Ireland]

I've been looking for the thread you mention David but can't find page 21.

[David Davis]

Hi Doug,

 

If you go to All Topics, then to Charity Mass Build 2011, then to Charity Mass Build Chat thread, which is currently on Page 2 ( not the Charity Mass Build In Build Chat thread).

 

Having got onto the right thread click on "Last" which will take you to Page 34. Click on number 29, then number 24, then number 21 and you'll get access to BEB's list.

[Biggles' Elder Brother - Moderator]

Hi Guys,

 

I've updated the roll call list - see here

 

BEB

[Ian Jones]

Thanks for all the congrats gents, much appreciated.

 

Ian.

 

Webbiteer No.19

[Ian Jones]

Okay so B test out of the way, bank holidays galore and windy weather - great opportunity for making some progress with the Webbit.

 

Just to recap, we've covered preparing the firewall for the engine mount and then I said that it was time to finish building the airframe before actually fitting the engine. I also mentioned that I wasn't going fit any servos until the engine was fitted so that the servo positions can be used to contribute towards balancing the aeroplane.

 

So over the next few posts we are going to fit the engine so that we end up with something like this:

[Ian Jones]

Trial fit the engine mount & if you are going to fit the front former then move the engine along the mount to suit. Whether fitting the front former or not remember to leave room behind the engine for the pipe work to be manageable.

 

Having found the correct position for the engine mark the centre of the engine mounting holes. I like to use the the point that came with my knife set for this as it not only makes a good mark but also it makes a locating indent for the drill bit:

 

If you have a drill stand, even a cheap one like mine then the next stage is fairly easy:

 

If you do not have a drill stand then you will have to be very carefull to ensure the that you drill accurately through the mount. Whatever method you use be certain that the mount is securely held by some mechanical means such as a vice.

 

Using a drill bit to match the mounting screws, slowly and gently drill the mount. This is another job that is worth taking your time with because if one mounting hole is a little bit out then you will have to hack away at the errant hole to be able to mount the engine. These mounts are not very big and such hacking can weaken them considerably:

 

When all the holes are drilled cut off any flashing that is left on the underside of the mount:

 

Edited By Ian Jones on 04/05/2011 00:40:05

[Ian Jones]

 

Engine Fitting

It is quite usual to fit the mount to the bulk head and then the engine to the mount but we don;t want to do that, no really we don't there just enough room unless we use self tapping screws to hold the engine and don't strain the whole thing getting them in. In this case that isn't an option because I do not use self tapping screws for mounting engines. I've known them to come loose even on a 25 size engine so it's nuts and bolt for me.

So the only realistic way of doing it is to attach the engine to the mount and then the mount to the bulkhead. If you followed my earlier instructions for the bulkhead then this will be a little bit fiddly but not impossible by any means as there is just enough clearance under the engine to get a screwdriver in to tighten the lower mount screws. The top mount screws will be a doddle if you are fitting an engine with a conventional side exhaust - my AP15 needed a little bit of rethink on that idea, as you will shortly see.

 

Anyway first things first - fit the engine to the mount using high tensile steel bolts and nylock nuts. If for some reason you do not use nylock bolts then you must fit a locking nut and use thread locker:

 

Tighten the nuts in a diagonal pattern to ensure even pressure all the way round and ensure the engine is sitting on the mount properly before starting because if the engine gets snagged part way along one the bolts and you keep tightening up the other bolt(s) then you risk breaking the mounting lug.

 

Don't go adding it to the airframe yet, we need to fit the tank & tubes first

 

 

 

[Ian Jones]

Preparing The Tank

Layout the clunk, clunk pipe and outlet with it’s rubber ‘O’ ring fitted. Place the outlet on the tank so that it represents it’s position when screwed in. Place the clunk so that it’s base is 5mm from the end of the tank; this will give the required 3mm internal clearance. Now you can lay the clunk pipe along side, cut it to the right length and assemble all the parts.

It can be quite tricky screwing in the fuel outlet without crossing the thread but the old trick of pushing on a piece of fuel tubing and turning it with your fingers does the trick.

I will only be using the fuel feed and pressure pipe and will use a short length of tubing to route the third outlet to one of the unused outlets at the side. I am doing this because the shortage of space in the engine bay will make routing another pipe a pain in the neck and as the carburettor feed pipe is easy to at there seems no point in making things more difficult than they need to be.

Connect up some fuel tubing and place the tank in the fuselage threading the tubes through the firewall. Cut the tubes to the required lengths and remove the tank again. Make all tubes airtight and fill a bowl or sink with hot water then completely submerge the tank. The hot water will warm the air in the tank causing it to expand revealing any leaks in the form of a stream of bubbles.

 

I like to put some foam at the front of my tanks for cushioning in a heavy landing and to ensure that the airframe does not touch the tank (which can lead to vibration in the tank and fuel foaming.

 

The exciting bit's next but I have to go to bed now and get some sleep ready for polling station duties tomorrow.

The next installment will be when I get back.

Edited By Ian Jones on 04/05/2011 22:42:05

[Ian Jones]

Right votes cast (and counted) so back to the engine installation.

At Last – Time To Actually Fit The Engine

 

This is going to be a little bit fiddley so a little patience is needed and everything will be fine.

 

First loosely put the tank in place, threading the tubing through the hole in the bulkead (aka firewall) in the process. Packing with foam just tight enough to stop the tank from moving will help stop it rattling about whilst working in the engine bay. The foam is also necessary to prevent engine vibration passing through the airframe and to the tank resulting in foaming fuel. Foaming in the tank results in bubbles in the fuel feed tube which will make the engine unreliable and impossible to tune.

If you are using piano wire with a ‘Z’ bend to connect it to the throttle arm then it would be best to do this now. Then when the engine and mount are offered up to the bulkhead the piano wire can be threaded through the hole in the bulkhead at the same time. Much easier than trying to connect it afterwards.

Now insert the engine mount screws through the holes in the mount and offer it (together with engine) up to the bulkhead. Thread the fuel tubing through the middle of the and use masking tape to hold the tubes out of the way. By far the easiest way to prevent the screws falling out in the process is to have someone (a beautiful assistant?) hold the fuselage pointing upwards whilst you do this and the more tricky next bit.

 

If you are fitting an AP15 like mine you will also need to route the silicone exhaust extension out through the hole in the engine bay floor. I think this is quite a neat way of dealing with the exhaust but if you want to avoid that complication you can unscrew the exhaust and use the washer(s) provided with the engine to make it point in the preferred direction.

 

Whilst everything is still loose it's easier to now route the pressure tube and fuel supply tube to their respective nipples.

 

If you hold the mount about 3/8” from the bulkhead you should be able to see where the screw threads are going. Tighten each screw just enough to ensure they will not fall out then slide the mount down the threads against the bulkhead. You can know tighten all the screws to secure the whole lot in place.

 

 

To tighten the lower mount screws you should just have enough space between the engine and the floor of the engine bay. If that has not worked out for you then the next post may be of some help.

 

Edited By Ian Jones on 07/05/2011 23:05:48

Edited By Ian Jones on 07/05/2011 23:30:53

[Ian Jones]

If the previous step worked out then all has gone to plan but it didn't quite work out for me because of the rear exhaust on the AP15. Somehow it just didn’t line up properly and I couldn’t get the screw driver to the top right engine mount screw. Hah! I thought the lower screws were going to be the problem!

A quick rethink later resulted in fitting a screw through the bulkhead from the inside. This needed to be screwed in very tight to form a stud in the engine bay.

 

Now the stud can pass through the hole in the mount and have a nut applied from the engine bay side. I’ve used an ordinary nut here because that’s all I had to hand but I will either apply thread locker or more likely replace it with a nylock. The same fix could possibly be used if you haven’t got enough clearance between the engine and the engine bay floor to get a screwdriver in – you would only be able to get small movements in with the spanner but it is a potential solution.

So I ended up with my screws looking like this:

Fiddly though it was, it has ended up as a neat installation and in the process I have hopefully found some solutions to problems that some of you may come across. After all that’s the idea of these example builds - to share experiences.

Edited By Ian Jones on 07/05/2011 23:23:22

[Ian Jones]

I used a thin nylon snake for my throttle to servo connection and this is the point at which I fitted it and then checked that the connector didn’t snag anywhere.

So the engine is fitted, there is free movement in the throttle connection and the tank is in place. On the subject of the tank – if you decide to place a length of wood across the back of the tank to stop it sliding backwards don’t forget to place some foam between the two.

All that remains is to connect up to the throttle servo and if you have already installed it then you can go ahead. I decided to leave all my servos until last and use them to help balance the aeroplane. I’m glad I did. The AP15 is so light that my webbit would have turned out incredibly tail heavy if I had already fitted the servos at the back of the servo bay as I had originally intended. I now have the opportunity to fit the servos well forward.

 

[Ian Jones]

Setting Up The Throttle Servo

Since I haven’t installed my servos yet and will not be doing so until I have the undercarriage fitted I will not have my webbit completed in time for the end of the “official” mass build period. In the mean time there might be someone that would like to know how I intend to set up the throttle servo, so here’s the theory (which I have used several times in the past).

• Rig up power for the receiver and connect up the throttle servo, switch on the transmitter and then the receiver.
• Set the throttle trim to it’s mid point. On some transmitters with digital trims the range is “-nn” to “+nn” and the mid point is “0”. On some others though the range is something like “0” to “30” and the mid point in this case is “15”.
• As the servo is now centred switch of the receiver and then transmitter.
• Place the servo arm on the servo so that the arm is at right angles to the servo body and gently press into place.
• Switch everything back on as previously described and check the servo arm remains at right angles or if you have inadvertently moved it that it returns to this position.
• Switch off again.
• Place a nipple connector on the servo arm and switch everything on again.
• Look into the carburettor and move the throttle arm so that the barrel is half open. Use masking tape to hold it in this position.
• Lay the snake over the connector and cut to the required length. The required lengthy being enough to allow for some adjustment in either direction should it be necessary.
• Remove the connector from the servo arm, loosely attach to the snake and reconnect to the servo arm
• Re-centre the servo by again cycling through switching on & switching off the transmitter and receiver.
• Ensure the snake is not buckled and tighten the connector’s locking screw. After the maiden flight apply nutlock to it, in the mean time ensure it is tight enough to do it’s lob but not so tight that it shreds the snake (that’s very tight though).
• Remove the masking tape from the throttle arm
• Screw in the servos arm retaining screw. (I leave it until this point so that any removal & refitting of the servo arm doesn’t stress the threads in the servo).
• Switch everything back on and use the transmitter’s throttle end point adjustments to set the travel so that the servo does not buzz at fully closed and fully open settings.
• Set the throttle cut (See instructions for your transmitter)
• Set initial failsafe position (Read and fully understand your transmitter instructions on this – all makes vary on how this is done, so presume nothing).

Why did I keep switching everything off? Just a precaution really. It’s very easy not to realise how much leverage is being applied to the servo arm when making adjustments or trying to get things to fit and leaving it the servo with power on will cause the servo to stall. I like to start off with good reliable servos!

Running in a new engine is really beyond the scope of what was intended for this example build but what I will say is… read the instructions that came with your engine, they are usually very similar for all engines but not always the same.

That’s it, the end of this example build though I will update this thread when I’ve fully finished my webbit.

I hope this example build has been/will be of use to some of you. Of course if I can help anyone then post your queries and I’ll do my best to answer them.

Happy building & joyful flying to all.

Ian

Webbiteer No.19

Edited By Ian Jones on 08/05/2011 00:54:39

Edited By Ian Jones on 08/05/2011 00:55:58

[Big Bandit]

Nice one Ian, very informative .

Cheers,

Chris.

[Ian Jones]

Thanks Chris, hopefully links in with for articles.

 

Ian

[Ian Jones]

Posted by Ian Jones on 02/04/2011 00:25:46:

Parts List

So to get down to business we need some parts:.....

 

..... I will be using one these smaller servos later in the WebBIT build but the operation of that is Top Secret at the moment.

 

The Extra servo - revealed:

[Ian Jones]

Posted by Ian Jones on 21/04/2011 22:42:39:

Posted by David Davis Telemaster Sales UK on 19/04/2011 19:43:27:

Hi Ian

 

I'd be interested in knowing how much your Webbit weighs when it's finished.

 

Mine weighs 3.5 lbs with a 25 four-stroke up front and a tricycle undercarriage.

 

I might but an AP15 like yours as my smallest engine is a ball-raced Irvine 20. How much do they cost and where did you get yours from?

 

Regards

 

David

Webbiteer No 15

Hi David, sorry to keep you waiting for a reply.

 

I'll weigh my Webbit when it's finished and post it here so that you will be able to pick up on it.

 

The AP15 cost me £39.99 from Barnstormers model shop which is my LMS www.barnstormersmodels.co.uk

 

Regards, Ian

Hi David

 

Completed weight of my Webbington Bomber is 2lb 14ozs. It would have been a tad lighter but that engine is so light that I had to add weight to the nose.

 

Ian

Edited By Ian Jones on 29/05/2011 19:49:15

[Richard Harris]

Webbington Bomber !!..LOL I like that Ian, looks great

[Biggles' Elder Brother - Moderator]

Looks great Ian - love the bomb!

 

Don't envy you figuring out which way up it is against an overcast sky once the bomb has been dropped though!

 

BEB

[Ian Jones]

Thanks Richard - not as "different" as yours though.

 

Hmm, BEB you are right. I thought it looked in all black but it isn't really practical so I've spent today putting some decals on that should help.

I've put a photo in the completed webbit thread but to save you going there:

 

I'm not sure which I prefer really.

Edited By Ian Jones on 29/05/2011 22:18:41

[Biggles' Elder Brother - Moderator]

Very smart!

 

BEB

[David Gilder]

Very good Ian

 

Good name..... My name would have been "Bumble Bee Bomber"!!!!

 

Cant wait to see it flying..... Still not maidened mine due to the high winds!!!

 

Dave

[Big Bandit]

Looking smart Ian, and when the wind finally drops, you'll have to give us a flight report.

 

Chris.

[Ian Jones]

Thanks chaps. I'm hoping that I can get a maiden flight in later in the week.

 

Perhaps I should have gone for a dambuster  bomb and "Barrier Busting Bumble Bee Bouncing Bomb Bomber"

 

Ian

Edited By Ian Jones on 30/05/2011 11:16:18