| GMS 25 check out by Tom Jolley |
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| Import
agents are CML Distribution. |
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This is not a shelf item. Ordered
31/10/06 & Postman delivered 10/11/06. |
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£49.00 incl P & P on your
precious permeable plastic. |
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| REMEMBER:
THIS IS ONLY ONE EXAMPLE |
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| What's in
the box? |
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Average
basic instructions/info with USA litigation in mind- Tower Hobbies |
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are the US supplier. Hex keys &
exh. gasket. And an engine + silencer. |
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This engine range has been around
for some time- included in MacGregor's |
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2000 cat- hence "GMS2000"?. *** |
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| Basic
informative details only here. I'll also spare you the usual magazine drivel. |
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| Silencer |
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2 pieces with one long bolt-
"normal" sort of layout. |
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No baffles/internals. |
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"Standard"
35 mm centres for attachment to case. |
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Angled
exhaust [tapered bore for casting]
6.4mm Ø @ outside end |
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&
6.0 mm Ø inside silencer. |
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| Needle
Valve |
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Remote- already assembled on a thin
sheet metal bracket. |
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To be fixed by you using the
existing top 2 backplate screws. |
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Needle taper & threads look
better than ASP: testing will reveal all. |
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| Carb |
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2 needle type. |
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Blanking
plug fitted to carb in place of needle valve assembly. This is a domed |
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nut
securing a stepped plug- it can be removed & the needle assembly |
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transferred from its rear bracket. |
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Metal arm for servo connection. |
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2 x "O" ring seals on
spigot to seal to case. Good push fit in case. |
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Secured by tangential draw bolt with
single nut. |
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| The
Big Bit |
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Backplate- |
Cast Al sealed with "O"
ring. |
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Shaft- |
Standard 1/4" UNF prop nut. |
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Although
cut away for balancing in the usual way there is a thin full |
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diameter disc adjacent to the rear
race (rigid but read expensive). |
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Al prop driver located by Al tapered
collet. ***** |
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Case- |
Both races have steel cages. |
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The front race has a single
rubber-faced metal shield (@ the front). |
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Info: the front race size is 8 x 19
x 6 for those who crash a lot. |
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Races were not
removed- alignment deemed to be OK. |
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Alignment
of passages with cylinder ports is good (and better than |
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some @ >£). |
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Head- |
Machined from barstock & fitted
with Cu shims. |
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No projection into bore (similar to
many- all?- Super Tigres). |
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Rod- |
Basic- no Irvine frills. |
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Bronze bushed @ both ends. |
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2 offset lube holes @ big end. |
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P & Cyl- |
A real ABC set-up: no OS peelies
here. |
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Edge of cylinder flange marked for
alignment with front head screw |
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for Chinese assemblers & easily
confused Americans. |
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Pin is 5 mm Ø, interference fit
& has Teflon end pads. End pads |
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were not removed so pin
wall thickness was not checked. |
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| Minute
amount of debris washed out during strip down. |
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| Good quality
workpersonship- how PC is that ??? |
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| Will
it fit in your existing models? |
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Bearer gap= 30mm, bolt ctrs= 38 x
15mm |
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The supplied rear N/V assy will be cramped by your engine mount if
you use |
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a SLEC '06B'. Move
it to the front & it's OK. |
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Weight
incl silencer= 362 g despite the literature saying 310- good for tail |
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heavy models. |
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Irvine= 336g, ASP= 323g |
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| The
REALLY interesting bit:- RUNNING |
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Standard Irvine C2K fuel |
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8 x 6 APC in an attempt to approximate "in air" revs |
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Unused Taylor standard plug |
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Test day 29 Nov 2006 over period
1230 to 1330 |
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Barometric Pressure 1026 mb |
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Temp variation: 12.5 - 11.0° C |
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Humidity 83 - 88% |
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Air Density 95.2 - 95.8 |
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Revs checked with 'TNC tach' ( $110!) |
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| Testing
sequence |
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GMS mounted on bench- this gives the
best results (mount rigidty) |
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14.8 - 14.9K |
Very
easy to needle |
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Best of two ASP mounted in model |
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15.4 - 15.5K |
Used OS remote needle assy. |
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Best of four Irvine mounted in model |
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15.5 - 15.6K |
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| Things
to bear in mind:- |
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The time period was a very limited
window. |
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At
this time of the year the weather was very good for engines. |
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The
plug used was in no way anything special & may not be the best for a |
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particular engine. I have time but
not that much time. |
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There will always be individual
variations between engines of the same make. |
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| Comments |
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| *** |
Some
manufacturers are ceasing/have ceased production of some of the |
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smaller
engines. Saito range now starts at 56.
OS are reported as deleting the |
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20FS-
and maybe others. Apparently this is because RTF/ARTFs are not being |
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produced
for this size- such models are for electric or bigger engines. You |
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only
need to look at the U.S. magazines to see the reality over there & it's |
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coming here to a retailer near you. |
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| ***** |
The
prop driver/collet fit developed wear during the running in/test process
(prop |
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changing)
& the close fitting driver started to rub on the front of the case. |
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Problem was solved by fitting a thin
washer between the collet & front race. |
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Good but not good enough
for groups 1 & 2 |
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Cheap entry alternative
for group 3? |
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Anybody want to buy a GMS25- one
owner, low mileage, never used in anger? |
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