Tipsy Nipper Owner's Group - Forum

Hi I have recently aquired ZS-UDT a Slingsby MK/111 c/n S.107
which has a 1600VW converted to 1835 and never been started. The a/c is a collection of parts in quite good condition but has not flown for 10 years. Both mags seem dead(Rockford slick 4001) and a local engine builder advises abandoning secondary ign. and running primary ign as electronic triggered optically by a standard VW distributor.
1/ I dont like this because of the considerable height blister needed on the cowling and wondered if Greatplains Compufire kit and distr.would fit under the cowling?
2/ SA CAA may demand secondary ign. so I have considered GPs oilpump drive secondary system but am concerned that it might not have space behind the prop. If so does anyone do a triggering disc to fit on the prop boss?
3/Have been given a M/cycle alternator (of unknown make) complete with a laser cut mounting spider (across the bellhousing). Hoped to get some help from Leburg on all the above but alas this is now not possible. The "spider"prevents one from remounting the big alloy plate for the mags so seems to prevent a mag/distr. combo. Has anyone a copy of Leburgs £5 booklet?
4/Having observed a RF5 with a WV1835 repeatedly overheat on take off (and sieze) I have developed a strong interest in VW cooling and am looking with an unapproving eye at the very rudimentary baffeling. Study of Limbach and Sauer engines has only produced more questions.
Can anyone advise on baffles includind the Limbach cylinder wraps and the GP bottom tins?
Maybe this enough to be going on with. Anyone with advice can reach me on a UK phone for the next few weeks (028)25 89 85 80. Many thanks Jantar

Hi Jantar,

Re the ign' system. The Great Plains distributer is low profile, so will probably fit under the cowling without too much of a problem. I am talking to various companies about a system that would be similar to the Leburg system......I will post details as they become available.

I personally think operating with only one ignition system to be rather foolhardy, even if the authorities let you do it. If you do go to an electronic system then you will need to install a charging system, again, I am in comm's with an oufit that may provide a system similar to the Leburg alternator installation........details to follow.

I would think the "Spider" for the mag' and alternator to take up too much room behind the engine. The VW is rather heavy to move forward to give you room, you will end up with serious C of G problems.

Re' cooling, there is every chance the ring gaps of the VW have not been set correctly. It is better to have them on the large size rather than tight. VW Heritage and various other suppliers sell what are called "Cool Tins". They fit under the cylinders and ensure the cooling air reaches underneath the cylinders also. But all of this is negated by poorly fitting baffles. I made my own, initially made cardboard ones and progressivley cut them back until the cowl fitted very close, then made them from alloy slightly larger, then progressively cut them down until I had a nice tight fit with a clearance of 5-10mm and fitted a lip seal to the edge. Over filling the engine oil can lead to oil overheating, as the oil picks up heat in the push-rod tubes, as can under-filling.

You will need an external oil cooler, with it mounted below the engine taking ducted air from an intake just below the spinner even if it has the oil heated inlet manifold. I have fabricated and am experimenting with an alloy inlet manifold with some internal trickery to provide an oil cooler also. I am hopefull this will allow me to do away with the external cooler.

Good luck with the project.

Neil

Hi Neil so glad to get a response!! Yes I have ordered GPAS Compufire driven by a low distributor which hopefully will just fit under the cowling. As secondary looks like I must recon the impulse mag and use it. GPAS have a secondary driven by the oil pump but I am not sure if there is clearance behind the prop. I have had some help from US sources re cooling and have ordered GPAS bottom "tins". The tip re checking ring gaps is new and much appreciated and will be checked as I will open the engine to"CC" and set a low comp.ratio( mogas in SA is very low octane) Will remake all the baffles as i am not happy with present fit and FELT "seals" am searching for rubber mould to fit baffle edge and flex.feather edge to seal at cowling but no luck so far. Recieved wisdom so far says divert about 80% of cooling air over ex, valve corners so am considering alloy boxes at heads for this. Of course it can all go sick on first T.O. but there is some time to go before that. Still struggling with proposed m/c alternator and will appreciate any further info. Will have to put recess in firewall.
Many thanks Keep in touch Jantar

Hi Jantar,

I personally would have "held off" the other ign' systems as a copy of the Leburg system based on the compufire system is the way ahead I think. I have the Leburg system on mine, with the motorcycle alternator on the back of the engine. I can forsee using the same alternator and a dual compufire system which uses remote triggers mounted on the edge of the alternator rotor. The alternator rotor and coil assembly is from a Honda CBR600, using an adaptor hub on the back of the crankshaft from Leburg. If I can get a hub to borrow and get the dimensions off of it I can get them made locally......price to follow. The CBR alternator you can buy off of ebay, just search for Honda CBR600 alternator. If you are shy of buying a second-hand stator coil set then there are new ones available. The same applies for the regulator which has two sizes, try to get the small one! The large one has a large finned heat sink.

My baffles work fine without fancy work around the exhaust areas, one thing that I have done, and not seen anyone else do or promulgate is to make sure all the "flashing" (thin alloy where the moulds meet) has been removed from between the fins on the cyl' heads, and also open out the small air-ways around the exhaust ports to allow the air to flow through. (No flow=no cooling) I use a dremel for the small openings, with a 4mm drill and use the side of the drill to do the work. (you will probably break some drill bits, but if they are new and sharp you should not have to load them too much) As the the flashing between the fins, hold the head up to the light and see what I mean. I use a grinderette with a flexible disc to get all the way up to the outside of the combustion chamber. I have not had any cracked heads or valve seating problems although my engine runs at full throttle almost all the time I am doing aero's, which is usually 20mins at a time, and most of the time!

I have spent as much time machining the heads for cc and gas flow as I have building the whole of the bottom end of the engine. The "cool tins" and cylinder base shims are available from VW Heritage: http://www.vwheritage.com/ as are plenty of other goodies.
When you come to cc the heads there is a very good tool at: http://www.johnmaherracing.co.uk/enginecalc.htm to work out shims and CR. BEWARE, small amounts of piston height make a very large difference. I would recommend fitting one piston/cylinder/head to do an ACTUAL clearance volume check at TDC. that way you can be absolutely sure of your calculations. (I use a 35cc ciringe, flat 10mm perpex discs, and engine oil to cc the heads.)

I have used a flexible edge seal from: http://www.sealsdirect.co.uk/bbCMS/shop ... rtmentId=3
You can use the ETS60 or ETS619, both work fine.

Good luck!

A little is going a long way! First have you photos or drawings of the m/c alternator arrangement a-la Leburgh? I have photos of my alt. and spider mount but am unwilling to proceed as m/c is unknown. Mine mounts the stator first on the spider followed by the rotor on a shaft let into the mag drive and gland nut on crank. Its a little tricky leaving space for mounting spider ,mag mount plate. duplex mag drive, but its possible. Have learnt recently that CBR600 rotor fits first followed by stator (ie. reverse order to mine) and vould like view of arrangement. My Compufire is driven by distr. and recieves advance timing by std. centrifugal system in distr. Any secondary is likely to be fixed timing----unless achieved electronically a-la Leburgh. That means you can trigger it from various sources but dont switch it on for hand cranking!! As I am 6000NM from my engine tell me exactly where are these "small air ways at ex.port" Surely not in the main fin zone, also in CC equalising exactly where do I remove metal in the head? Thanks for all the links but something is wrong at vwheritage as microsoft keeps disconnecting me from net!!! Used to be baffled Jantar many thanks

Hi Jantar,

I have been pulling my hair out with this computer.......I have messed about with some photos, so here goes!

Nope! the confuser won't have it..........its says the board attachment quota has been reached! Send me your email address so I can send it direct please.

Neil

Hi Jantar,

I have spoken to Paul and he has fixed the website.......bingo!

Two photos here, they have yellow arrows to indicate the area on the cyl' head that can be machined to cc the head. I suggest you offer up a cylinder to the head, scribe a line around the inside of the liner on the cyl' head face so you know where you can machine up to. If you look very closely you can see where I have scribed a line. The picture is two heads, one has been cc'd and ported but not polished, the other is untouched. It may be slightly different to yours as these are "big valve" heads.

My heads are seriously worked. The ultimate is to keep the "squish" lands on the heads as tight as possible to the piston, so if you have to use thick cyl' base shims you loose the squish clearance. So in my heads the combustion chamber cc has been taken from 51cc to 56cc, the valves have 3 angles cut on them to increase valve seat efficiency, also the ports have been hand machined to increase gas flow in this area also.

I have various die grinders, electric and air driven, however a dremel will work with some alloy burrs. (ebay, these are quite good but very cheap: #150342793152 (put that number into the ebay search)) You are looking for a smooth finish, polishing is not mandatory.

The other photo shows the areas you need to check around the exhaust ports. Make sure you address the area between the fins at the head ends also.

Neil

Great ! very clear. I continue to learn,the bit about squish closeness is new. I suspected that the ex.port cooling might be down through that area but none of my photos looked down there! I can see why its desirable to include those zones within the side baffles. Bob Hoover of Sonerai fame recommends a small plate wired into the centre underside (inlet port zone) to restrict flow here and presumably divert more towards exh.zone. Thank God for yellow arrows!!
On the alternator(m/c) subject I did some head scratching re the mounting of the stator.
I have been misled by the unit given to me where all is mounted via the bell housing. Reincluding a mag interferes with this and using a unit where the stator lies aft of the rotor interferes beyond reasonable resolution. The mag chain wheel drive moves everything aft 30mm. and well thro the firewall, so I have decided that a new "spider" holding the rotor and fixed to the cockpit end of the engine mount bolts could be made rigid enough to serve and remain centered within the rotor(which will be mounted on a rearward extension of the crankshaft) It looks possible to maintain the integrity of the firewall using a flanged recessed box. Assembly would be tight but not impossible. How does this equate to the Leburg arrangement? E- mail :- strela1962@hotmail.com Phone /fax. 02825898085
Regards Jantar

Hi Jantar,

I would not block off or restrict any airflow around the heads, if the air is moving then it is being replaced by cooler air, and with the Nipper there is so much air being driven into the cowling that it will make no difference. By the s/n of your aircraft I am assuming you are using the full cowl set?

You will not be able to center and control the location of the stator coils enough to ensure correct radial clearance by mounting the stator coil set on the firewall. Also assembly and mounting the engine will be very difficult without damaging the stator or the rotor. I recommend you go down the Leburg set-up and do away with the spider all together, possibly replacing your alternator with the CBR one, they are not expensive via ebay, and have proven reliability.

Neil

Yes it has a full cowling and your point is taken. I did come to UK with intention of going the Leburg road but sadly this was not possible thus the quest for alternatives. Have no objections to purchasing CBR 600 alternator BUT have no information on how to mount the stator. The rotor drive/mounting seems straighforward extension of the crankshaft which I can have machined in SA. On the other hand mounting the stator coils is unresolved. Either it is attached to the bell housing using something (a spider ? ) or to the fuselage at the engine mounts,----- or am I missing a third alternative? and there is the problem of limited space!
A photocopy of the design would solve this. The E-bay burrs are fantastic thanks for the info.
If you have any further information on the Leburgh arrangement for CBR alternator I should be most grateful and will stay away from the drawing board! Regards Tom H

Hi Neill, now a few months down the line and now have fitted.
1 Compufire system one of.fitted. Distributor was still a little high (about 5mm ) so cowling needed small mod.
2 Leburg system from Henry.fitted.
3 M/C alt. ex. honda 125 sorry i got CBX rotor and stator from different sources on E-bay and they dont seem a match---but without dimension data could not proceed.
4 Elect.fuel pump. Facet.* Dist. displaced original. Also I needed space for a hand made air filter. Very dusty here. * Am told Mitsua is better !
5 New brake system--cycle/hydraulic-- looks good.
6 New rec/reg-- the one from e-bay although new was scrap!!
7 Rebuilt baffles with extra felt on sides/front and a great fitting rubber moulding at rear.
8 Removed mech.rev counter from panel and in its space fitted all new switches and circuit breakers Replaced tacho with 50mm digital on a side panel.
9 Cut/extended stb front ext.pipe 50mm and can now access all the lower spark plugs
10 In firewall fitted a box to take extra depth of m/c alternator and covered 40 years of random openings to restore fire resistance to the firewall!!. Done with care using same gauge steel and 3mm steel screws with locknuts as 3.2 or ANY steel rivet is unobtainable here
11 Have installed 90% of wiring but ground to a halt as I wait explanations /specs for some items on the Leburg wiring diagram.
12 RE vamped original fuel filler cap--better but I dont like it!
13 Discovered a silicone which is PETROL RESTANT
14 Discovered a great source of rubber grommets.

STILL TO DO
15 Pull all cables , clean , inspect, and coat with lanolin ( not found yet) can anyone suggest alternatives or I may have to go sheep rustliing!
16 Remove ALL bolts and pins and replace same with original spec.( have complete set from Nipper Kits0
17 Replace U/C rubbers
18 Fit/obtain oil cooler
20 START ENGINE (will do this soon)
21 Probably tear engine apart and have it cc,ed and balanced.
22 Inspection and reregistration as EAA

I can almost see the light at the end of the tunnel. Jantar

Hi Jantar,
Well done, sounds like you are progressing well.
Re' the small baffle plate at the bottom of the cyl' head in the center you mentioned a while back, I understand now what you were referring to, yes it is a good idea, VW did fit them as std, and as you say may help drive air around the exhaust area. Did you fit the "cool tins" from GPAS?
Ref:
4: Where have you mounted the fuel pump?
5: Who's brake system did you use?
8: Is this the tacho' GPAS do? I understand it also has an hour meter on it. How does it get its signal from the ignition system?
11: What wiring diagrams do you need, I can email you them.
13: Petrol resistant silicone.......where are you using it?
15: Have a look at: http://en.wikipedia.org/wiki/Lanolin it may give you some ideas where to get it. In the absence of it use a light coating of engine oil. ( http://www.vitaminlifehealth.com/Liquid ... 28MLKC.htm )
16: I need to replace my u/c rubbers also. I have a special tool for doing it, but think a pair of bars that go through the lugs the rubbers wrap around which are spread by threadstock would be better and much more controlable.

Incidentally, if you have not noticed, the pic' of my cyl' head shows the RH one unmachined, you can just see the scribe line of the bore on the combustion chamber, the LH one is machined.

Also, just to clarify: Make sure you macine any "flashing" off of the head fins between the fins just below the ex' ports. I have seen head severely restricted here. I use a "floppy" grinderette disk.

Good luck and well done! Post some pic's for us please, it is great to see how the project is going.

All the best,

Neil