electrical system --Help---

[Guest Teenie2]

I have a small prob ,hopefully someone can head me in the right direction.

 

OK, my teenie has a VW engine with no electrical generation system fitted. There is no way a conventional alternator would fit.But i would like to fit a very small fuel pump to help prevent fuel vapour locks .I could fit a battery and recharge on landing ,but for the moment this option is not practical.So I need to design something,one option Ive thought about is flexible solar panels over the top of the aft fuselage (expensive, ugly) another idea is attached to the spinner backing plate magnets and on the front of the engine windings (an alternator ). I must admit i am not to sure how to manage that .Or even a slipstream powered generator (draggy,and thats the last thing I need).

 

Any suggestions ?

 

 

[Yenn]

Do you think you can run a fuel pump from solar or a cobbled up generator without using a battery?

 

I have my doubts, and if I am correct you will still need a battery, which brings you back to your own option of using and recharging.

 

Way back when aviation was young fuel was pumped by pressurising the fuel tank. That would solve your problem, but it is not a safe option. A manual fuel pump could be fitted for use when vapour lock is suspected.

 

Probably best would be to re-route the fuel lines to keep them cool and eliminate places where vapour could get held. That means a steady rise all the way to the engine fuel pump.

 

 

[Guest Teenie2]

Actually the tank has slight positive press due to forward facing vent (bent alloy tube).

 

I have no mechanical pump at all.The carby is located beneath the engine so I have a steady fall from the tank to the carby and with a full tank vapour locks should not be a prob it is only with the tank near empty the problem could occur ,especially in the plastic penny filter.

 

 

[icebob]

Hi Teenie2,

 

I had a similar problem with my Volkplane1 in the 70's I changed the fuel line location and had the plastic filter on the end of a sort of U shaped solid fuel line away from the engine as far as i could without snagging stuff, i also spent a day silver soldering about twenty brass washers on the fuel line on each side of the fuel filter, it worked ok.

 

Bob.

 

 

[geoffreywh]

forget it

 

I really think you are pushing your luck trying to build a generator! Wow! what an undertaking..and where would you put the regulator? ... If you cant fit a battery (and why not? small sealed batteries can be mounted anywhere and at any angle..even a pack of nicads would do it. ) On my boat (from a previous life) I had a rubbery squeeze thing in the fuel line to remove vapour locks.. Check out a big boat place...That worked fine.....Geoff

 

 

[wanabigaplane]

Is this really a problem ?

 

If your carburettor is gravity fed, and vapour has filled the fuel line, surely when the float opens the valve to demand more fuel, the fuel and vapour will flow into the bowl and there would be no problem ?

 

If, in real life, this is really a problem, would it not be fixed by installing a second line to the top of the tank from where the present fuel line enters the carburettor?

 

If pressure really is required, why not install a fuel squeeze bulb as used in outboards ? I had one in my Sapphire but never had the need to use it. The rubber deteriorated over the years of previous ownership, and it became another thing to maintain. With the extra fuel line wandering a torturous path to the hand of the pilot to fix a problem that didn't exist, I eventually deleted it, and never missed it.

 

Jack. :):)

 

 

[Guest Teenie2]

Thanks guys ,I am trying to cover all my bases .I feel i have to look at every part of the fuel system following a crash that I still really don't know the cause.I have got some good ideas off a yank forum site i visit. They suggest a forward facing vent to slightly pressurize the tank.

 

The prob with the squeeze bulb idea is if the carby bowl runs low on fuel it gives a miss then stops,since I have no starter motor ,pumping the bulb is not going to do much.

 

 

[icebob]

Hi Teenie2,

 

I just had one of those AHHH moments, are you using 1/4 inch fuel line? If so have a look at the US web site, they are all using 3/8 or bigger? I increased the fuel line size with my VP1 and it fixed the fuel starvation problem below half a tank of fuel especially in turns and with my previous post that fixed the vapor lock issue.

 

I noticed that on the US web site that a lot of the VW motors were fitted with the standard VW mechanical fuel pump and some with the VW 40 amp alternator bolted on the rear of the motor(my VP1 had both)

 

Bob.

 

 

[sain]

Doesn't Great Plains sell alternators for VW engines? They seem to attach to the crankshaft, rather than to the spinner backing plate like you were saying. I'd be worried about unbalancing the prop if you were attaching magnets to the backing plate.

 

Anyway, pretty pictures of one of the alternators being installed: http://bobhooversblog.blogspot.com/2007/06/av-reliable-ignition.html

 

Great Plains site:

 

http://www.greatplainsas.com/scindex.html

 

 

[Yenn]

If the engine stops, does it actually stop turning, or will it windmill.

 

When I did my training we had to do a restart in flight and that was not using a starter motor.

 

Turn off the fuel and when the noise stops, pull the nose up to stop the prop.

 

Fuel on, then push the nose down to just below VNe and wait. It took a little while before the prop did one compression, then a pause and another couple of compressions, all the while the sheep arre growing in size. Then lovely sound as it roared into life. I have never done it again as the times I have lost an engine i have not had enough height to play around.

 

 

[Guest Teenie2]

I have not had the nerve to try, but on some of the Air vw sites in the states they state that even at VNE a VW will not rotate.

 

Anyway I tried something a bit unusual today,if a vapour lock is going to form it will be at the penny filter, so what i did was whilst the engine was running I applied heat (with my wifes hair dryer) to the filter for about 10 min (must admit I was getting nervous,6 inches away from a spinning prop blowing hot air on a fuel filter)no major lock evident ,the fuel level did drop in the clear filter though.

 

 

[icebob]

Hi Teenie2,

 

You are correct my VP1 had the 1800cc VW engine and on engine stopage would not turn over to restart in flight. However at around normal cruse speed it was a very short spurt on the starter to get it going again.

 

Have you seen the VW engines on the US site with starters and mechanical fuel pumps?

 

Bob.

 

 

[icebob]

Hi Teenie,

 

I have run the VP1 and with engine stopped the penny filter is full, at idle it is at about 80-90% full and at 1500rpm it is about 70-80% full.

 

I set up a small camera, actually a reversing camra in flight at max rpm the penny filter is still over 50% full. I hope this helps you to pin point the problem.

 

 

[Guest Teenie2]

Thanks icebob ,do you fly the VP1 at the oaks ? Love to have a look. My penny filter is about 50% all the time (idle and high power).I think the filter needs to be purged of air before fitting.Ill have a go on Friday.Are you still running the VW ?

 

 

[jetboy]

we've had a Hapi VW that has the magnets in the flywheel end and a stator coils putting out 10 amps or so. Very similar to Jabiru. Most motorbikes have them? This particular one cracked the flywheel and was replaced with a belt/pulley mounted there and a dynamo from the John Deere / Kubota parts dept. and it works OK. B+C in the US sell a similar alternator, about 8 amps worth.

 

As your electric requirement is less, it is feasable to make your own. I made a unit from a stepper motor ex old computer equipment. connected the wires to 2 sets of bridge rectifier diodes you can tell which windings do what by shorting them and turning the shaft. Got about 1 amp from this one it was 3" dia. I get a lot more out of a DC drive motor from an ancient mainframe computer printer (these are the ones that would take your arm off if you get in the way, DEC LA-120)

 

Most fuel pumps wont need a regulator

 

Ralph

 

I have a small prob ,hopefully someone can head me in the right direction.OK, my teenie has a VW engine with no electrical generation system fitted. There is no way a conventional alternator would fit.But i would like to fit a very small fuel pump to help prevent fuel vapour locks .I could fit a battery and recharge on

[icebob]

Hi Teenie2,

 

I have my VP1 at a friends farm near Riverstone, once i get it registered i will indeed fly to the oaks.

 

you may not have an air issue as such, with my engine running flat out the penny filter is between 50-60% full but i do have the VW mechanical fuel pump fitted. The whole kit(starter and fuel pump) of the better quality comes from the US at about $700(US).

 

I also changed my whole fuel line size from 1/4 inch to 3/8inch and got rid of a lot of problems.

 

What size motor do you use?

 

Bob.

 

 

[Guest Teenie2]

1835 ,actually Ardem (moded VW from the late sixties).No room for a starter the back of the engine is up against the firewall.No room for the fuel pump (engine driven).

 

 

[Guest Teenie2]

Ok I did the flow check on the fuel system (drain plug in the carby bowl) 9 litres in 15min,thats pretty good. Once with the filter purged of air and again not purged,and there was no difference in flow.

 

 

[icebob]

Hi Teenie2,

 

That flow is good, so it is not that as an issue. So from the tank to carbie is not a problem of fuel flow as a static test. My engine at idle with the mechanical pump was giving me 12-14 lts per 15 min so the differences between our fuel flow rates are not that great. I just have a bigger volume of fuel to the carbie.

 

What actually happened in the first place to concern you?

 

 

[Knighty]

Mikuni Vacuum Fuel Pump

 

Hi Teenie

 

Just come on line and read your posts. Jetboy mentioned the John Deere dynamo, I have seen these used on William Wynnes engines that he builds (Corvair flat 6), they weigh minimal with enough output juice to keep the battery charged.

 

See http://www.flycorvair.com/ for the charging system, buy local from John Deere as Jetboy suggests.

 

As for your fuel pump why not use the vacuum Mikuni's as per Rotax, HKS, stationary 4 stroke engines, outboard engines etc. All you need to do is run the vacuum from your inlet manifold to the pump and route the fuel line as needed. I have questioned the vacuum in the inlet manifold on a 4 stroke at full throttle and told that there is more than enough pulsed suction to operate the pump. Who am I to argue! Pumps can be purchased direct from Wade Marlo (Wadeair at Orange/Springhill Airport). You wont have to muck around with an electrical systems then, save $$$ time, effort and weight.

 

Cheers

 

Knighty

 

 

[Guest Teenie2]

The fuel pump idea is great,I had just assumed that the four stroke would not produce enough of a crankcase pulse to operate the pump.Ill try taking the oil cap off whilst the engine is running and see what I can feel.Just reread your post ,you said inlet manifold,that just might work.

 

 

[Knighty]

Yes Teenie

 

Inlet manifold matey, you will get bugger all pulse out from the crankcase breather on a 4 stroke!

 

I will be very surprised if it doesnt work. I have a spare vacuum pump in my 582 bits and peices which is brand new never used however it has 2 outlets. Unless you have 2 carbs or decide to route the 2 into one it still can be used. Let me know if you are interested and we can work something out.

 

Cheers

 

Knighty

 

 

[Yenn]

Don't be too optimistic about inlet manifold pressure being able to pump fuel. I worked on the "autovac" years ago. It was used instead of a fuel pump and was basiclly A tank connected to the fuel tank and mounted above the carby, with manifold vacuum drawing fuel in and automatic valving to make it all work. It was about the size of a large jam tin and worked well when the throttle was not full open. Unfortunately when full throttle is required it doesn't work too well and you had to lift your foot to get more fuel when it coughed. We also had vacuum wipers working on the same principle. They worked real well until you went to overtake a truck on a wet day, and they waited until you were just in the wake from the wheels of the truck and then stopped.

 

If you want some idea of the viability of vacuum, just fit a temporary vacuum guage and you will find that at full throttle there is no pressure drop.

 

 

[Guest Teenie2]

This weekend I will pull the primer line off and see how much pulsing I get.

 

 

[Knighty]

Hi Teenie

 

What did you find out about your pulse???

 

Knighty