Belt Drives and design

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rv7charlie

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only do it for a few firing strokes after engine stroke
Did you mean 'after engine start'?

Recognizing that this is coming from an engineering-ignoramus, has a cog-belt system ever been designed with spring tensioners on both sides of the pulleys, to act like the springs in a clutch plate? Or would it be too heavy/cumbersome/hard to tune, compared to just using something like a Guibo?
 

wsimpso1

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Did you mean 'after engine start'?

Recognizing that this is coming from an engineering-ignoramus, has a cog-belt system ever been designed with spring tensioners on both sides of the pulleys, to act like the springs in a clutch plate? Or would it be too heavy/cumbersome/hard to tune, compared to just using something like a Guibo?
Thanks for the catch. Yes, I meant after start. I took a look a bit ago, found that one and a couple others and fixed them. I think you find it reads better now.
 

plncraze

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In response to Dan's question about anyone here really building a drive here are pictures of mine. It is a 2000 Chevy Metro engine bored .040 over with the head milled down a bit. There is a factory clutch held down with a piece of steel . The splined trans shaft goes from the clutch plate to a Lovejoy C 38/45 with a red Shot A spider. A 1.25" 4130N shaft goes from that coupling through a bearing to the first sprocket then into another bearing. The large sprocket gives a three to one ratio. The goal is to have a pusher prop far enough back to avoid any significant wakes from the rest of the aircraft. In the Holzer numbers that I have posted were for the clutch/crank assembly, the clutch springs and Lovejoy were not included, the 4130N shaft, the two small sprocket, the belt the big sprocket, a Ford Mustang axle and finally a propeller MMOI number I got from a Rotax discussion.
Bill ski was kind enough to list a brief list of what to do if one were to design a belt drive in another thread. Using that and Dan's numbers for his Suzuki have gotten me to this point. Thanks guys!!! I will start playing with the Holzer numbers with a lighter big sprocket to see if I can get the numbers happier. Until then here are some pictures16269023596248210834902010878899.jpg16269023871198866330662292316296.jpg16269024124976777499365536951904.jpg
 

DanH

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Pln (uh, do you have a real name?), help me understand your plan.

The sprockets, belt, and propshaft are fixed to the airframe, while the engine will sit on soft mounts?

Have you established accurate inertias and spring rates for every component? No point in a GIGO exercise. You should not use any of the numbers I posted. Twenty years later even I don't accurately know what design iteration those numbers represented.
 
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AdrianS

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Did you mean 'after engine start'?

Recognizing that this is coming from an engineering-ignoramus, has a cog-belt system ever been designed with spring tensioners on both sides of the pulleys, to act like the springs in a clutch plate? Or would it be too heavy/cumbersome/hard to tune, compared to just using something like a Guibo?
That was what I was referring to.

But from Bill's post earlier, the deflection would be tiny, so the spring rate required would be interesting, given that you have to have some deflection of the belt even at full tourque.
 

plncraze

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Dan, my real name is John and I am sorry that I was too vague about which numbers of yours I was using. Here are the numbers of yours that I was talking about that I mentioned above. "...a little I-3 Suzuki that made 68hp on the best day of its life." "At 1800 RPM, wide-open throttle oscillating torque is 2300 lbs.-ft." And finally "...now look at a 4000 cruise RPM. Vibratory amplitude is around 50 lbs.-ft." Those numbers give an envelope of performance and loads which help define what the drive will have to tolerate. All of the above quotes are from the VAF website.
I plan to mount the engine and drivetrain like on a BD-5 but without the one-way clutch because I would like to avoid the free-wheeling prop with an engine failure. I had not even thought about engine mounts yet. Are soft mounts better at minimizing engine movement relative to the drive?
I have done the initial MMOI with a bifilar set-up as you had suggested in a paper you had posted online. The only number that I used directly from your most recent list was the stiffness of the belt. I have not seen this number anywhere else.
My hope is that the friction clutch against the flywheel will give me the same result as Jeron had with his dry friction surface in the upper shaft.
The shaft spring rates are calculated from their material which is 4130N for the lower shaft and 4140 for the upper shaft.
 

Bigshu

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The prop and engine are turning together in steady state, but the vibe is engine and prop moving opposite each other. Every firing stroke the engine tries to go faster than the prop and between firing strokes the engine tries to go slower, and little bit more energy gets added to the vibration on every cycle.
So, could you put a one way clutch in there to take away the "engine trying to run slower" energy? There's some pretty famous planes that used Dynaflex couplings to act like a torque converter. I wonder how hot the flow charge got inside?
 

dog

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Dan, my real name is John and I am sorry that I was too vague about which numbers of yours I was using. Here are the numbers of yours that I was talking about that I mentioned above. "...a little I-3 Suzuki that made 68hp on the best day of its life." "At 1800 RPM, wide-open throttle oscillating torque is 2300 lbs.-ft." And finally "...now look at a 4000 cruise RPM. Vibratory amplitude is around 50 lbs.-ft." Those numbers give an envelope of performance and loads which help define what the drive will have to tolerate. All of the above quotes are from the VAF website.
I plan to mount the engine and drivetrain like on a BD-5 but without the one-way clutch because I would like to avoid the free-wheeling prop with an engine failure. I had not even thought about engine mounts yet. Are soft mounts better at minimizing engine movement relative to the drive?
I have done the initial MMOI with a bifilar set-up as you had suggested in a paper you had posted online. The only number that I used directly from your most recent list was the stiffness of the belt. I have not seen this number anywhere else.
My hope is that the friction clutch against the flywheel will give me the same result as Jeron had with his dry friction surface in the upper shaft.
The shaft spring rates are calculated from their material which is 4130N for the lower shaft and 4140 for the upper shaft.
Will the "lovejoy" coupler handle the inevitable
missalingments of the engine relitive to the belt drive and how the engine moves in its mounts?
The design I am working on hinges around
CV joints , attached to the big pulley,with most of the TV bieng handled on
the flywheel,with the belt drive attached and moving with the motor.
I would like to have belt tensioning and alignment built into the bearing mounts for the big pulley.With any changes handled by the
CV joints in the driveshaft.
Like your design,not having the prop mounted to the belt drive will help with simpler belt changes and inspections.
 

AdrianS

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Will the "lovejoy" coupler handle the inevitable
missalingments of the engine relitive to the belt drive and how the engine moves in its mounts?
The design I am working on hinges around
CV joints , attached to the big pulley,with most of the TV bieng handled on
the flywheel,with the belt drive attached and moving with the motor.
I would like to have belt tensioning and alignment built into the bearing mounts for the big pulley.With any changes handled by the
CV joints in the driveshaft.
Like your design,not having the prop mounted to the belt drive will help with simpler belt changes and inspections.
When we use CV joints at work, they are always setup with a slight dog-leg between the shafts so the CV's run at a few degrees of angle.
This extends the life of the CV.
 

Kiwi303

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En Zed. Aka The Shire.
That makes the grease move around and improves lubrication, if they run around and around never moving other than straightforward rotation, the contact patches eventually get dry and can wear. deliberately making them shift around a little bit makes them stir their packing grease up a bit and covers all the contact surfaces.
 

dog

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Good to know about offsetting the cv joints to prevent premature wear,and it gives me room to adjust where stuff goes for CG and structural members.
Thanks, cause I would have spent time trying to line everything up perfectly.
 

daveklingler

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I don't want to spoil this thread, but it should be pointed out that Aeromomentum has a reduction drive that's designed for Suzukis, very lightweight, exceedingly well-tested and fairly priced.

I see that you've (OP) said that you want to mount the engine like in a BD-5, which might preclude the use of a gear drive, but I thought it should be mentioned.
 

plncraze

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I am hoping the Lovejoy will allow some misalignment. The splined shaft should too.
I am aware of other reduction drives but all of them cost thousands of dollars.
 

plncraze

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Thought of the day: "*Forcing frequency out of a 4 cycle IC engine is one-half the product of the shaft speed and the number of cylinders." Still studying and will provide some newer Holzer stuff when I have time
 

plncraze

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Has anyone here tried to open the Holzer.plt file from VibrationData and if so what did you use? I tried TurboCad and some freebie online crap and got nowhere.
 

plncraze

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Here is a picture and print out of where I am now with this. Saturday morning is when the time, focus and caffeine lines all cross on the graph LOL. I am using Holder from VibrationData and the MMOI spreadsheet that Dan and Billski supplied. The next move I see is trying lighten the number 3 inertia and also trying calculate what the anonymous coupler ( above the pink number 1) do to shaft stiffness16271354886068331249281755802327.jpg16271354886068331249281755802327.jpg
 

dog

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plncraze
Here is a picture and print out of where I am now with this. Saturday morning is when the time, focus and caffeine lines all cross on the graph LOL. I am using Holder from VibrationData and the MMOI spreadsheet that Dan and Billski supplied. The next move I see is trying lighten the number 3 inertia and also trying calculate what the anonymous coupler ( above the pink number 1) do to shaft stiffnes

What knid of computer/OS are you running the
Holzer program from vibration data on?
Looking for suggestions to purchase desk machine or a phone that will run linux and if possible then the Holtzer code.[/QUOTE]
 

plncraze

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The Holzer program is written in dos and probably can be run on any desktop you can find. If I were shopping for a computer to do this I would get my requirements and go find a used system.
 

dog

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The Holzer program is written in dos and probably can be run on any desktop you can find. If I were shopping for a computer to do this I would get my requirements and go find a used system.
Did a quick search and found a bunch of dos
emulators for android,which is happy news.
I can pay up at vibration data and see if I can get the holtzer code to run on my phone.
Got a bluetooth keyboard and will get a screen
my phone will cast to.
Machinerys Handbook was in my mailbox when I got home yesterday,all kinds of good stuff ,formulas for flywheels and balancing anything,tables,conversion charts,2500 pages of good stuff.
 

Stealth

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Just so you know, this is belt design guide is for applications like 3D printers. very small. Not for engines.
for vehicles you might try this one instead:
 
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