Exhaust extensions
In normal operation, the engine exhaust flow is continually expanding as it leaves the 2nd stage. Adding
extra exhaust ducting to the exhaust outlets inhibits the exhaust expansion and causes local restrictions
to the free flow, increasing the back pressure on the engine. This reduces the power available to run the
engine and has to be made up by burning more fuel. This therefore significantly increase the running
temperature and spoils the starting and running characteristics of the unit, so is strongly discouraged.
Where the standard exhaust outlet does not quite reach beyond the ends of a particular bodyshell short
simple push-on straight exhaust stubs up to 75mm/3” are acceptable as they cause minimal disturbance
to the engine flow. It is the longer lengths or changes in direction which cause back pressure and must
be avoided.
Fitting the clutch
1. Fitting clutch. To fit the fan and clutch to the gearbox output shaft
you need to lock the output shaft.
Do not attempt to do this by
jamming the 2
nd
stage turbine
.
2. Remove the four M3 screws from the
bottom
cap of the gearbox
to reveal access to the lower output shaft nut which you can hold
stopped using an 11mm socket wrench or ring spanner.
Be extra vigilant not to allow grit or dirt to enter while the cap is
removed. Be aware there may be some loose fuel in the gearbox
so best not do this on unprotected best dining table..
3. Place the 3/8” thin washer onto the output shaft first
before
the fan to ensure running clearance
to the top bearing.
4. A 12mm socket or box spanner can be used to nip the brass nut onto the fan. You can use a
washer if one was supplied in the heli kit but it is not usual. Do not use locking compound (Loctite
etc) on the brass nut. Do not substitute the brass nut, the shaft is stainless steel to prevent
rusting as is the brass nut.
5. Tighten the side nip screws on the split collet if used. Check fan rotates freely. Fit the clutch parts
and ensure everything is tracking true.
6. Refit bottom cap on gearbox (note orientation of cutout to clear input gear) using a small drop of
blue locking compound on the screws.
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