Today's Message Index:
----------------------
1. 05:32 AM - Re: Double Belt Drive (Archie)
2. 05:58 AM - Re: Double Belt Drive (Phil Flaugher)
3. 06:33 AM - Belt and gear drives (Gary Casey)
4. 07:16 AM - Re: Double Belt Drive (Jerry Reynolds)
5. 10:41 AM - Re: Double Belt Drive (Tedd McHenry)
6. 10:46 AM - Re: Double Belt Drive (Tedd McHenry)
7. 03:31 PM - Re: Double Belt Drive (Ed Anderson)
8. 03:39 PM - Re: Double Belt Drive (Archie)
9. 04:41 PM - Re: Double Belt Drive (Charlie & Tupper England)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Double Belt Drive |
--> Engines-List message posted by: "Archie" <archie97@earthlink.net>
Good thinking Tedd,
These are the things that makes Experimental aircraft so great.
Innovation!
Heck, the store bought aircraft manufacturers still can't get it
right after 50-70 years, with continuous AD's.
All the disadvantages you listed are valid, but might be overcome
to a degree.
At this point, believe that the easiest would be the additional length.
The additional streamlining would be an advantage, and the cg factor
is easily corrected. Get to work!
Archie
===============================================
> --> Engines-List message posted by: Tedd McHenry <tedd@vansairforce.org>
>
> I've recently had an idea that's probably crazy, but I'm interested in
other
> people's thoughts on it. For a rotary installation, the offset that a
belt
> drive provides isn't required, and is actually a liability in some
> installations. My idea is to use a two-stage belt drive. The first drive
is
> connected to the output flange of the crankshaft in the conventional
manner.
> But the driven pulley is on an idler shaft with another pulley that drives
the
> second stage. The driven pulley of the second stage is concentric with
the
> engine output shaft and connected to the prop flange.
>
> Each stage provides half of the total reduction ratio, so the two drive
pulleys
> are the same size and the two driven pulleys are the same size.
>
> Advantages:
>
> The redrive output shaft is concentric with the engine crankshaft.
>
> Tighter packaging (vertically and laterally). Each stage contributes half
of
> the overall reduction ratio, so the two large pulleys are smaller than the
> driven pulley would be in a single-stage redrive. Also, the smaller
difference
> in diameter between the driving pulleys and the driven pulleys means that
the
> shaft spacing can be closer (i.e. smaller "center distance factor").
Overall
> the reduction in the frontal area should be significant.
>
> Disadvantages:
>
> Cost, weight, more parts to fail, and longer.
>
> ---
>
> Tedd McHenry
> Surrey, BC
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Double Belt Drive |
--> Engines-List message posted by: "Phil Flaugher" <phil.flaugher@charter.net>
Wish I could see a sketch........anybody capable?
Phil
----- Original Message -----
From: "Tedd McHenry" <tedd@vansairforce.org>
Subject: Engines-List: Double Belt Drive
> --> Engines-List message posted by: Tedd McHenry
<tedd@vansairforce.org>
>
> I've recently had an idea that's probably crazy, but I'm
interested in other
> people's thoughts on it. For a rotary installation, the offset
that a belt
> drive provides isn't required, and is actually a liability in some
> installations. My idea is to use a two-stage belt drive. The
first drive is
> connected to the output flange of the crankshaft in the
conventional manner.
> But the driven pulley is on an idler shaft with another pulley
that drives the
> second stage. The driven pulley of the second stage is concentric
with the
> engine output shaft and connected to the prop flange.
>
> Each stage provides half of the total reduction ratio, so the two
drive pulleys
> are the same size and the two driven pulleys are the same size.
>
> Advantages:
>
> The redrive output shaft is concentric with the engine crankshaft.
>
> Tighter packaging (vertically and laterally). Each stage
contributes half of
> the overall reduction ratio, so the two large pulleys are smaller
than the
> driven pulley would be in a single-stage redrive. Also, the
smaller difference
> in diameter between the driving pulleys and the driven pulleys
means that the
> shaft spacing can be closer (i.e. smaller "center distance
factor"). Overall
> the reduction in the frontal area should be significant.
>
> Disadvantages:
>
> Cost, weight, more parts to fail, and longer.
>
> ---
>
> Tedd McHenry
> Surrey, BC
>
>
======
>
======
>
======
>
======
>
>
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Belt and gear drives |
--> Engines-List message posted by: "Gary Casey" <glcasey@adelphia.net>
<<The first drive is
connected to the output flange of the crankshaft in the conventional manner.
But the driven pulley is on an idler shaft with another pulley that drives
the
second stage. The driven pulley of the second stage is concentric with the
engine output shaft and connected to the prop flange.
Each stage provides half of the total reduction ratio, so the two drive
pulleys
are the same size and the two driven pulleys are the same size.
Advantages:
The redrive output shaft is concentric with the engine crankshaft.
Tighter packaging (vertically and laterally). Each stage contributes half
of
the overall reduction ratio, so the two large pulleys are smaller than the
driven pulley would be in a single-stage redrive. Also, the smaller
difference
in diameter between the driving pulleys and the driven pulleys means that
the
shaft spacing can be closer (i.e. smaller "center distance factor").
Overall
the reduction in the frontal area should be significant.
Disadvantages:
Cost, weight, more parts to fail, and longer.
Tedd McHenry
Surrey, BC>>
Tedd, I think you have it right on all counts. It would depend on the
relative value you place on the advantages and disadvantages as to whether
it's a good idea. And there are some factors that make it not as bad as it
could be: The belt loading could be contained within the shafts in a way
that you wouldn't have to double the structure - the input and prop shafts
could be concentric, for example. One disadvantage of any belt drive is
that the center distance required will surely require some kind of "chin" in
the cowling right behind the prop. Also, the belts would not likely be the
same as the second stage belt carries much more torque than the first stage,
requiring it to be wider.
I like the "I-X" (Internal-External) gear drive that someone builds as it
keeps the prop offset to a very reasonable value and the tooth loading is
very low. I've wondered if one couldn't use the largest drive gear possible
so that the external gear just fits in the normal flywheel diameter. This
keeps the tooth loading very low and the torsional stiffness very high.
Mount the drive gear directly to the crankshaft and use no soft couplers at
all - the idea is to make the system so stiff that torsional resonance is
outside the normal operating range. The normal flywheel area would have to
be sealed, but the original crank seal would be removed, allowing engine oil
to lubricate the gears. Very efficient, very light and rugged?
Gary Casey
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Double Belt Drive |
--> Engines-List message posted by: "Jerry Reynolds" <flyguy50@bluemarble.net>
Time: 08:53:11 PM PST US
From: Tedd McHenry <tedd@vansairforce.org>
Subject: Engines-List: Double Belt Drive
--> Engines-List message posted by: Tedd McHenry <tedd@vansairforce.org>
I've recently had an idea... to use a two-stage belt drive....
Tedd,
Regarding the above.. both belts would not need to be idential in HP rating,
less torque on engine belt. But identical or not, my concern would be that
both need individual tension adjustment, as the torque, wear, and stretch,
will be greater on the output belt. I've never seen auxillary tensioner
rollers used in aircraft, as might be used on other mechanical belted
equipment, but no expert here. So the pulley spacing needs to be adjusted
for tensioning. While it might be nice thinking of a mutual intermediate
bearing support between the engine crank shaft and the rear of the prop
shaft, (not a bad idea, considering the side loads imposed on the crank
shaft)... I'd think, they would have to be separate, so that the output belt
could also be tensioned properly. Just makes the assembly more complex,
with 2x adjustments and associated hardware. Tension adjustment would
require the whole system to be loose, adjust engine belt first, by moving
the whole idler shaft/double pulley assembly, then adjustment of the output
belt, by moving the whole prop shaft/bearing assembly. Wouldn't be
perfectly concentric then, but don't see why it wouldn't work. NO idea
about possible resonance issues. I have seen in-line planetary gear
reductions previously, which are truly concentric, and small. No further
info on those however.
Jerry
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Double Belt Drive |
--> Engines-List message posted by: Tedd McHenry <tedd@vansairforce.org>
Thanks to everyone for your comments on my compound drive idea.
For those who found my explanation weak, here are some pictures that I hope
will clarify the concept. Should have shown them in the first place, I guess.
http://www.vansairforce.org/projects/mchenryt/project_notes/CompoundDrive/
Regarding loading and belt sizes, here is how I understand the situation.
Jerry pointed out that the primary belt carries less torque than the secondary
belt, and I believe that's correct. Also, both belts carry the same power
(since torque and speed vary by the same ratio). So the primary belt could
probably be slightly smaller, but for simplicity it might be best to use the
same dimensions for both stages of the drive. I think belt size is affected by
both torque and speed, but I'm no expert. My only experience in designing belt
drives is small synchronizing drives, not power transmission drives.
Another issue is tension and differential belt stretch. Again, I don't know
enough yet to properly assess the problem. My hope is that pulley 1 and pulley
4 could remain concentric (perhaps even mounted on a common shaft, as Jerry
suggested). The ideal sitation would be to simply adjust the tension of both
belts simultaneously by moving the idler shaft. That might mean replacing both
belts when the more highly loaded secondary belt stretches beyond a certain
point. Failing that, pullies 1 and 4 could be mounted separately, so that the
secondary belt can be adjusted independently of the primary belt, using the
method that Jerry described.
Regarding resonance, I think the natural frequency of the system would be lower
than for a single-stage belt drive, because the same applied torque stretches
two belts in series. (For an analogy, think of two rubber bands attached
own.) Unfortunately, I don't know if that's a good thing or a bad thing! I
suspect it's bad, because I think the objective is normally to have the natural
frequency of the drive higher than the excitation frequencies of the engine and
prop. On the other hand, this drive is much more compact (i.e. shorter belts)
than a single-stage drive, which would tend to raise the natural frequency.
Obviously, this is something I need to investigate further!
Someone also mentioned using an internal-external gear arrangement to minimize
the offset between input and output shafts. I think that's a great idea. I
believe the drive Jan Eggenfellner uses on his Subaru conversions is of that
type. But I don't feel I can engineer and fabricate my own gear drive, whereas
I think I probably could manage a belt drive.
Tedd McHenry
Surrey, BC
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Double Belt Drive |
--> Engines-List message posted by: Tedd McHenry <tedd@vansairforce.org>
By the way, does anyone know if it's necessary to use a flywheel on a rotary
engine conversion? My compound drive would be a lot easier to mount without
the flywheel in the way.
Tedd McHenry
Surrey, BC
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Double Belt Drive |
--> Engines-List message posted by: "Ed Anderson" <eanderson@carolina.rr.com>
----- Original Message -----
From: "Tedd McHenry" <tedd@vansairforce.org>
Subject: Re: Engines-List: Double Belt Drive
> --> Engines-List message posted by: Tedd McHenry <tedd@vansairforce.org>
>
> By the way, does anyone know if it's necessary to use a flywheel on a
rotary
> engine conversion? My compound drive would be a lot easier to mount
without
> the flywheel in the way.
>
> Tedd McHenry
> Surrey, BC
>
Ted, depending on exactly what you mean by "Flywheel" the answer may be that
its not necessary. The Mazda Flywheel for the manual transmission version
of the engine weighs 20-30 lbs. Of course, thats a lot of iron to have to
haul around. Those who fly with a planetary gearbox use the automatic
transmission "Flex Plate" they both perform similar functions - transmit
power from the engine eccentric shaft to the transmission shaft and provides
a place for the starter ring to be mounted. The Flex Plate weights around 5
lbs as best I recall - considerably less that the "Flywheel". I would
think you would need some mechanism to transfer power to the gear shaft as
well as someplace to mount a starter ring.
Ed
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
Message 8
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Double Belt Drive |
--> Engines-List message posted by: "Archie" <archie97@earthlink.net>
> --> Engines-List message posted by: Tedd McHenry <tedd@vansairforce.org>
>
> By the way, does anyone know if it's necessary to use a flywheel on a
rotary
> engine conversion? My compound drive would be a lot easier to mount
without
> the flywheel in the way.
>
> Tedd McHenry
> Surrey, BC
Yes, They are externally counterweighted for balance.
Archie
Message 9
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Double Belt Drive |
--> Engines-List message posted by: Charlie & Tupper England <cengland@netdoor.com>
Tedd McHenry wrote:
>--> Engines-List message posted by: Tedd McHenry <tedd@vansairforce.org>
>
>By the way, does anyone know if it's necessary to use a flywheel on a rotary
>engine conversion? My compound drive would be a lot easier to mount without
>the flywheel in the way.
>
>Tedd McHenry
>Surrey, BC
>
You need the balance weights that are mounted on the flywheel or flex
plate. Tracy Crook's planetary drive uses the auto transmission flex
plate (lighter than a flywheel) to mount the balance weights & the ring
gear for the starter.
Charlie
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|