snips..

I understand there is a pusher in Fla. with a 13b

that uses a combination alternator, vacuum pump off of
a  chevette diesel engine (izusu?) I haven't checked
into it yet, but it might be a good way to reduce
weight.   Comments?  Jim Coffman

That sounds like Greg Richter's Cozy according to Chrissi it

failed.

At OSH he had a aircraft vacuum pump on there and that failed

on

the way up.

Paul Lamar

My personal experience using aircraft vacuum pumps with the 13B

was

unsatisfactory.  The small  aircraft engine vacuum pump is not

designed

for

operation higher than around 3600 rpm - maybe 4000 rpm for

limited

amount of

time.  I found that when I had the pulley sized so that it

provided

adequate

vacuum at low rpm (below 3000 engine rpm) the pump was soon

worn

out

and

graphite dust at the higher engine rpms.  When I increased the

size

of

the

drive pulley so that the vacuum pump lived at engine speeds of

5500-6000

rpm, it did not produce adequate vacuum at low engine rpms.

I went through two aircraft vacuum pumps in six months and

decided

to go

with the Mazda smog pump even though it was heavier.  I have

found

it

works

fine - just damn heavy. Perhaps someone else who has tried

aircraft

vacuum

pumps has a success story.  Lets hear from you.

Ed Anderson

Hi Ed,
My ex. Lyc. vac. pump driven by a toothed belt slower than it would

run

normaly has done 62hrs so far. No evidence of black carbon on the

outlet. My

engine idles at 2000RPM. (Slower on landing, for a bit of extra

drag.)

Ian RV6A

Great Ian. Send us pictures and/or drawings of the mounting block and
aux shaft. Are you interested in making more and selling the adapter?

Paul Lamar

How is the vacuum at the low end of your rpm range?  I still have my old
belt driven mechanism - perhaps I just got a bad vacuum pump, they were
rebuilds.  What size pully do you have on each end, What is the diameter

of

the Main pulley and Vacuum pump Pulley?

Ed Anderson

 I will measure them next time and let you know.

Ian

 
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