VW exhaust scheme

[JimCrawford]

Has anybody got any photos of their exhaust installation - cowlings off - that they could share? My Nipper has the 4 downward open pipes arrangement but they are crudely made of mild steel and won't last for long.
I'd like to fit a system made in stainless and a silenced arrangement wouldn't go amiss as I hope to move to a farm strip and wouldn't want to cause any problems with neighbours. Any suggestions to set me on the right track will be appreciated.

Jim

PS. Leburg installation is complete and engine runs will be started when the weather improves.

[G-ARBG]

Hi Jim,

I attach some pictures of a modified exhaust I fitted.

David
'RBG

[JimCrawford]

Thanks David, that looks like a good starting point to copy. I like the hot air pickup inside the cowling.

I have a secondary problem with my existing set in that the port forward lower spark plug points directly at the port fwd exhaust pipe and the right angle plug cap and ignition cable are very close. It is a Rollason Ardem conversion.

There are some details of the firewall on your photo which are also interesting, see firewall thread.

Happy New Year

Jim

[G-ARBG]

Jim,
Ref your firewall query see attached.

David
'RBG

[JimCrawford]

Good Evening Dave,

Thanks for that picture which is surely worth a thousand words!

I have concluded that the top fixings should be flush with the top edge of the firewall and that the Nipper drawing I have is in error. It would look rather strange for the top of the cowling to stick up 10mm from the line of the fuel tank and I'm sure I would have noticed that whenever I looked at various aircraft.
So, as I have to pull my cowling down hard to get the top fasteners engaged, either the fasteners of the bottom part are not low enough or the whole firewall is mounted 10mm too low - which would also imply that it is too short as it has to finish just above the nosewheel steering arm. Some careful measuring need here methinks. Would it be possible for you to measure the edge to edge height of your firewall? The two halves of the cowling seem to fit together well so I don't think that is a part of the problem.
An interesting detail I notice on your pictures is that your fastener mounts are fitted through the narrow parallel edge whereas mine are mounted on the triangular face. The drawing implies that your scheme is correct, but I've lost faith in the drawing details.
You have that depression in the firewall. Is that to accommodate the Honda alternator? I haven't found that necessary because I increased the length of my engine mounts by 3mm which gives me the absolute minimum clearance between the highest point of the alternator and the firewall. I'm only accepting this because the engine is hard mounted to the aircraft frame, if it were on anti-vibration mounts I would have had to make a much greater clearance.
Also you seem to be using the lightweight coils. I was disappointed to find that the skycraft kit included the heavier type, I had been led to believe that they were going to supply the lighter ones. I was also disappointed by the cables which came with the set. For the ignition on my Taylor Monoplane I've just bought the controller units, I'll source everything else myself. Making up aircraft cables used to be a part of the day job.

Thanks once again for your help

Regards

Jim

[Neil Spooner]

Hi Guys,
I experimented with loads of different ex' systems as I was at a noise sensitive strip....the best solution is twin pipes, perforated at the end and 50% crimped, inside "cans" that were also perforated......picture attached.
There are two designs here, the one with the red heat muff worked well, but was made from mild steel and eventually failed, the second one is stainless, worked well and is still in service.
There are inexpensive J tubes which have again become available which are a great source of stainless from which to fabricate your system:
https://www.justkampers.com/071755st-st ... -1979.html
Depending on what carb' you are using you will need a good hot air supply, this is best found as close to the ex' flange as possible, and preferably also drawing air from just behind the cylinder head, also preferably utilising heat from two ex' pipes. Pictures to follow.
Best wishes,
Neil

[Neil Spooner]

Hi Jim,
Beware moving the engine forward " because I increased the length of my engine mounts by 3mm ", it will move your CofG forward. Adding weight to the tail is self defeating and adds to the moment of inertia of the a/c which can adversely affect spin recovery. It is quite feasible to reduce the length of the stand offs between the outer and inner leburg alternator plates, and also to use countersunk bolts on the rearmost plate. You will need to be very careful the gland nut does not touch the stator windings, and it may be necessary to machine down the gland nut by 2-3mm. This will still leave enough nut to tighten to the correct torque.
Regards
Neil

[Neil Spooner]

This is the later system I am currently working on, but I have not flight tested it yet, and suspect it is not good for noise. The photos do indicate the hot air pick up that I am promoting. If you have a stromberg of other fixed choke carb' then a good hot air supply is a must.
This is a Mk1 version, the Mk2 has a much better clearance to the firewall and a better fit to the rear of the cyl' head.
I will post photos of the Mk2 shortly.
Regards
Neil