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mgraves(at)usmo.com
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 Posted: Fri Dec 15, 2006 3:56 am Post subject: Kolb-List:engine replacement /Valley Big Twin |
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speaking of engine replacements
For those that may not have seen it yet. Valley Eng, of Rolla MO. has installed one their Big Twin 4 stroke industrial engines, featured in this months SPORT PILOT magazine, and seen at OSK. on a Kolb Twinstar. It is replacing single carb Rotax 503 on the Twinstar
http://www.culverprops.com/big-twin.php
I am not affiliated with the Smith's in any way, just passing some possible useful info along
Monty
[quote][b]
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Fri Dec 15, 2006 5:52 am Post subject: Kolb-List:engine replacement /Valley Big Twin |
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| I am not affiliated with the Smith's in any way, just passing some
possible
| useful info along
| Monty
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Hi Monty:
I find this quote from Valley Engineering a little hard to believe.
This is in reference to the Kolb mkII and its test flight.
"They were worried that the new location of the prop; 5"higher than
it had been before would affect trim."
I think Rick Nielsen would also question this.
john h
mkIII
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Fri Dec 15, 2006 6:05 am Post subject: Kolb-List:engine replacement /Valley Big Twin |
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Hi Gang:
Sorry about that.
Had an incomplete quote in my previous post. Now it is fixed.
john h
| I find this quote from Valley Engineering a little hard to believe.
| This is in reference to the Kolb mkII and its test flight.
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| "They were worried that the new location of the prop; 5"higher than
| it had been before would affect trim. The plane flew just like it
did before the engine change "
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| I think Rick Nielsen would also question this.
|
| john h
| mkIII
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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NeilsenRM(at)comcast.net
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| Posted: Fri Dec 15, 2006 12:14 pm Post subject: Kolb-List:engine replacement /Valley Big Twin |
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Normally there is a big difference when the thrust line is moved up or down
by 5 inches. I know this because I have done exactly that. In the case of
the Valley Big twin it may not have had much effect. The Valley Big Twin
would be a marginal engine in a MKII. Something like maybe a 503 in a MKII.
A high thrust line problem is only a problem with lots of thrust. This
engine may have also moved the CG of the MKII more aft.
I would think the Valley Big Twin might make a good engine for a Firestar
but again you want to be concerned with a high thrust line. I talked to
these guys about the same redrive for my VW. They said that they tried it
but it burned the belts and pulley. I have some concern with this type of
harmonic dampening solution. My understanding is that the belts are allowed
to slip in one direction. The problem is that wear on these parts could
allow slippage in both directions. Now maybe you can detect the additional
slippage and would start gradually if at all. Maybe you just replace the
belts every 300 hours like you replace 2 stroke cranks. I just don't know.
Time will tell. Definitely a discussion point for Gene Smith. In general I
like the idea of this engine. Hey if you fly 2 strokes you are always flying
on the edge of disaster anyway.
Rick Neilsen
Redrive VW powered MKIIIc
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kfackler(at)ameritech.net
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| Posted: Fri Dec 15, 2006 12:27 pm Post subject: Kolb-List:engine replacement /Valley Big Twin |
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| Quote: | the Valley Big twin it may not have had much effect. The Valley Big Twin
would be a marginal engine in a MKII. Something like maybe a 503 in a
MKII.
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I certainly don't pretend to have your engineering expertise, Rick, but I
beg to differ on the 503 being marginal on the Mark II. Even on the hottest,
highest DA days I get 600 fpm of climb. On a modest day, it's 800 and a good
day is 1000. I can cruise all day at 5300 rpm giving 60 indicated and
burning 3.2gph. I can also cruise at either 65 or 70 if I'm willing to burn
a tad more juice. Please note that I'm flying every flight at gross weight
because I'm a rather portly fellow who weighs in at 260.
-Ken Fackler
Kolb Mark II (under a Rotax 503) / A722KWF
Rochester MI
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NeilsenRM(at)comcast.net
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| Posted: Fri Dec 15, 2006 2:27 pm Post subject: Kolb-List:engine replacement /Valley Big Twin |
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Ken
Sorry but marginal is a rather subjective term. When I was flying my direct
drive VW I didn't consider it marginal. I even flew a early MKIII with a 503
with over 400 lbs of passengers and it didn't seem marginal. Now get in a
80HP Rotax powered MKIII and you will understand. I'm sure the Johns will
tell you a 80 Rotax is marginal. You have very respectable performance
figures but once you fly one of the big kolbs with 80-100 redrive engine you
will instantly recognize the transformation and you will agree your plane is
marginal in Kolb or my terms. Also I really don't know the MKII that well
and maybe it does better than I think it does with the 503.
Also my "engineering expertise" ????? Fat dumb and happy is a better
description.
Do not archive
Rick Neilsen
Redrive VW powered MKIIIc
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Sat Dec 16, 2006 5:50 am Post subject: Kolb-List:engine replacement /Valley Big Twin |
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Monty,
..... Big Twin 4 stroke industrial engines, featured in this
months SPORT PILOT magazine, and seen at OSK. on a Kolb
Twinstar......
Do you happen to know the specs on the BIG prop they are using on the
Twinstar? Typically the Smiths make very large diameter props for
superior take-off/climb thrust. Zoom in on their photo from behind the
Kolb without the wings mounted. That prop is BIG!
Thom in Buffalo
do not archive
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Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
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mgraves(at)usmo.com
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| Posted: Sat Dec 16, 2006 6:38 am Post subject: Kolb-List:engine replacement /Valley Big Twin |
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Yes,
The ratio of the redrive is 1.66 and it swings the big prop static at 3500 rpm.
Prop is a Culver wood 70 inch diameter, 30 inches of pitch 70x30
pulls 245 lbs with this prop static. I was there when the test was done.
Dick Starks (infamous KC dawn patrol) the owner of the Kolb, pulled his
single carb Rotax 503 at 250lbs static. different day different
scales, and I was NOT present for this pull test.......... so its not
entirely a fair comparison, but the 4 stroke is in the ball park with the
SINGLE carb Rotax 503 for sure. Weight is almost the same when the 503
exhaust is considered within 5 lbs. And it costs less than a new single
carb 503.
I personally don't think it will pull and perform as much as the dual carb
Rotax 503. And I would agree it is a marginal choice for a 2 seat
KOLB.......I personally think two small people..... the engine will do fine
in the two place Kolb..... couple of lard butts like me, might be a
different story.......I talked to Starks again yesterday on the phone. We
have had a beautiful week of DEC weather here in MO, and they have flown
the Kolb almost every day this week. He is STILL really happy with the
switch. Still less than 10 hrs total, so as the wise man said..........
time will tell..,,,,,,,,
specs on the converted engine
http://www.generac.com/GeneracEngines/EngineModelsVTwinH.asp
990cc horizontal shaft mode.
Also a nice write up of Gene and Larry Smith in Dec issue and this
engine, in SPORT AVIATION.....at OSK
They have aprox 8 of these engines flying now, most in tractor config most
on WWI replicas ........ Starks Klob is the only one in pusher config.
Don't confuse this GENERAC engine with a Briggs, they are two totally
different engines.
Smiths also did some testing with a shorter prop........ Culver 64x34
pulls 240 lbs static at 3200 rpm
Monty Graves
At 08:49 AM 12/16/2006 -0500, you wrote:
| Quote: |
Monty,
...... Big Twin 4 stroke industrial engines, featured in this
months SPORT PILOT magazine, and seen at OSK. on a Kolb Twinstar......
Do you happen to know the specs on the BIG prop they are using on the
Twinstar? Typically the Smiths make very large diameter props for superior
take-off/climb thrust. Zoom in on their photo from behind the Kolb without
the wings mounted. That prop is BIG!
Thom in Buffalo
do not archive
|
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NeilsenRM(at)comcast.net
Guest
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| Posted: Sat Dec 16, 2006 8:24 am Post subject: Kolb-List:engine replacement /Valley Big Twin |
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Monty
Please keep us posted on that Valley Big Twin. I just looked at the specks
on the engine. I'm not sure what all the Smiths have done to the engine but
there is plenty of room for performance improvement. The chart on the engine
shows the torque falling off just as you get to the working part of the RPM
range we fly at. A modification to the cam would fix that and not effect
reliability much if at all.
On my redrive VW I run the same RPMs (engine and Prop) as the Valley Big
Twin and found major performance improvement by using a high performance cam
and high lift rockers. Initially I figured I went too far with the valve
lift and duration so I tried stock rockers. The stock rockers cut 500 RPMs
off my climb RPMs so I went back to the high lift rockers. My cam just
starts to make torque in the 1600-2500 RPM range. It is interesting trying
to keep a fixed RPM on approach to landing because my engine will not stay
at one RPM in that 1600 to 2500 range. There is very little load from the
prop below 2500 engine RPM so this works well. The important part is that I
get maximum torque in the 3000-3600 range were I fly and need it. The other
up side is that engine efficiency is also best in the 3000-3600 RPM even
with part throttle. When I look at the torque chart for the Generac I see
that torque has fallen off just were you need it. I believe you should cam a
redrive airplane engine to get maximum torque right at maximum RPMs.
Again my opinions are worth just what you are paying for it.
Rick Neilsen
Redrive VW powered MKIIIc
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