Exploding Fan New Style Housing

Factory-Fit

Tuning a 38" 23 hp Vanguard, got a stock flywheel lightened and tested to 6,500 rpm, Performance Vee Twin billet rods and high comp pistons and their 'Chevy grind' cam working billet roller rockers. Started it on stock ignition setting then dismantled to set to 8° extra advance. The motor fired first time after priming, no choke; starter hitched up to Son's
Fiat battery spins the engine like a top.


About to sort out the right tuned length for the headers, and a lightweight collector box and silencer. Today the thing ran really well, picking up rapidly if a little jerkily but that should yield to playing with the pilot air screws.

Then it happened... Crunch! running at middle revs and the huge plastic fan they fit on the latest engines disintegrated, taking the black plastic coating off the Magnetrons, bulging the casing and generally knocking hell out of the
ignition parts.

I daren't fit another fan now, but had heart set on being super reliable using
forced cooling.

Repaired now and test run without the cowling, but this is a serious setback; the fan will be cheap enough and a little panel work will sort out the cowling damage, but what if it does it again?

The older Vanguards had a smaller red casing and fan, I've never heard of one
letting go like this. Anyone advise? Mudbuddy limit their Vannies to 5200 rpm and I'm sure it was well below that speed.
Kev

BGW

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fstg21

Please don't run it without the pipes. It pains me to see.

Also,
Here is your savior..http://www.arcracing.com/servlet/the...-Briggs/Detail

Adjustable timing hub and SFI Rated.

BTW the newer housing cools better. Keep it.

Factory-Fit

Please don't run it without the pipes. It pains me to see. (snip) BTW the newer housing cools better. Keep it.[/QUOTE]

Billet flywheel = no generator, but thanks for the link anyway Sir.

Does running it without pipes as in WW11 Mustang stubs harm the motor? I've only run it up for testing the new bigger starter motor.

Thanks for the tip; had a copy of the old red housing and saw the difference in size compared o the new black type.

Al Hodge just said the problem is the lack of bracing across the front of the fan when you delete the mesh screen, the brass mounting lugs are stressed by the centrifugal force, hence my failure.

Have found four A4 size 3M self adhesive carbon-fibre sheets on eBay, intend cutting out the panels on the cowling and applying these over as infill panels, to both remove the damage and save weight.

Sulking 'cos my nice new cowling is all battered you see ;-(

All tips appreciated

Kev

sho305

I have not heard of this failure before, makes sense that if you modified the fan that would have caused it. Yes it sucks when you mess up something new, been there before. I assume you will re-jet it before you blast off into space. Wow that is a cool belt drive.

Factory-Fit

Thanks, drew it on CAD about twenty times and a man in India made the parts, he is a Welsh guy, running an ultralight company over there. He understands light and high quality finish, although I did all the calcuations for the belt type and width. Ace Aviation he calls his operation if you want a copy.

Also thanks for the comment about re-jetting but thought blue flames was OK? At the time was running the timing at stock setting, bought an advance key and am sure they work well, but wanted to be able to experiment. This meant mounting the Magnetron ignition units on small alloy strips and packers to move them round. Tried eight degrees and four degrees extra advance, the higher number gives really nice revs but occasionally stalls the starter when it kicks back. Four degrees gives better starting.

Still worrying why it does harm to run without pipes, can you add to my small knowledge of this please?

Reason for posting all this was to warn others, the mesh screen looks good bolted to outside of the cowl but something needs to go back on to tie the screen mounting lugs together

Cheers

Kev

DOOmsman

The valves are very hot and when you shut down the air can cool them
too fast and warp them.

sho305

It means nothing about jetting on a stand, you have to jet under load in the end configuration.

Timing advance will typically give more power over 2500rpm or so.

You can cheat and kill the ignition until the starter is turning good, to get around a kickback. If your cam still has the comp release you can vary it with valve lash but many cams eliminate it. You can get a high torque starter too, lot of people have to with billet/lightened flywheels and no comp release.

Factory-Fit

*Been there, got that T-Shirt, cam is a Chevy grind from Al Hodge, no compression release so already had to buy the heavy starter. Cam has a LOT of overlap, really designed for higher revs than I'll be using but he says it will be OK.

Thanks for reminding me about switching on only after spinning the motor, on the bench so just running the short wire to the casing to stop it, so will need three hands now to choke, operate starter and fiddle with the ignition switch..

If it gives more power over 2500 then the full advance at 8° is going back on!

Kev

sho305

I assume your prop will not fully load until your upper rpm right? Because more timing can lead to preignition at low rpm, but if you don't have load down there its not a problem really. They don't bother with much advance on lawn engines because they only run 3600 anyway. The magnatron does advance but not much I read. Actually I think it retards at low rpm.

Larger wire to your starter will give more power but of course its heavy. I guess putting the battery close would be the best bet, as shorter is better too.

I usually set the choke to not go on all the way, though lot of engines now put holes in the choke plate to do that. Then it will run at full choke until you get a hand free to dial the choke back.

The dyno runs I have seen on small engines for Kart racing/etc show that. You don't get a big increase but some. It depends on the compression and cam as to how much timing you need and I don't know how to figure that out. More compression is usually less full advance. Most of those guys run about 28-30 degrees total advance I read, though a flight or marine engine will typically have conservative settings compared to ground racing. They also mod these for swamp boat engines you might find some info there as that is also constant full throttle loading like flight use is.

drag racer

Awesome video, especially without any exh pipes on! I think that's the first time I have ever seen a piston engine run like that.

Link or URL where you got the rods & pistons from???