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  1. #81
    CB750 Enthusiast KIRBY's Avatar
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    Is the chordal wear because of being bevel? Would helical spur gears last longer? I can design it with spur gears. In fact, it would be easier. Round Bearing holes in the hub, but no bevel profile cutouts.
    Last edited by KIRBY; 04-05-2020 at 11:42 AM.

  2. #82
    CB750 Guru amc49's Avatar
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    Actually I'm somewhat wrong there, chordal action is reserved for chain drive not gear to gear. Gear to gear has close to the same issue with velocity ratio variation.

    Chordal issue comes from the size of the teeth, look at the pic you added of differential gears, how big the teeth are. Because they are expected to not be used that much and they have to be certain size for strength since they are smaller due to riding inside diff case. Bigger the teeth, the bigger the velocity change.

    A 'spur' gear is automatically a straight cut one, not helical by the definition. The bigger the gear tooth spacing the more chordal action.

    You are going to have utter fits just with the side gears as they need to be big enough to handle power interference from BOTH sides (2 engines), you intentionally want them to fight each other. And yet they have to work ALL the time, making them need to be even bigger. I envision you tearing them up pretty quick, you are overloading them way beyond design criteria.

  3. #83
    CB750 Enthusiast KIRBY's Avatar
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    Thank you for the explanation.

    Quote Originally Posted by amc49 View Post
    Actually Chordal issue comes from the size of the teeth, look at the pic you added of differential gears, how big the teeth are.
    Actually, the picture I used was one of tiny gears for use in RC cars. I would imagine full size care gears would have more teeth .


    Quote Originally Posted by amc49 View Post
    A 'spur' gear is automatically a straight cut one, not helical by the definition.
    Guess I should have said a spur gear differential design substituting helical cut gears for smoothness and quietness.

    Quote Originally Posted by amc49 View Post
    And yet they have to work ALL the time.
    No, only during up shifts when different ratios are present. Most of the driving would be in matching gears.

  4. #84
    CB750 Guru amc49's Avatar
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    'Most of the driving would be in matching gears.'

    I have to ask why after so much argument over having the 'half' gears.

    You're already doing what I predicted you would and before it's even built. Rendered the need for the second trans and entire diff as moot. It IS you know.

    Can't remember the maker but at some time in the dark past somebody took a DOHC 750 and put it in some sort of a narrow trike and sold it.

  5. #85
    CB750 Enthusiast KIRBY's Avatar
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    Quote Originally Posted by amc49 View Post
    'I have to ask why after so much argument over having the 'half' gears.
    The trike is much heavier than the bike, and I'd like some sportiness to it.

    Quote Originally Posted by amc49 View Post
    'You're already doing what I predicted you would and before it's even built. Rendered the need for the second trans and entire diff as moot. It IS you know.
    I want the power of two 750s, and it was already answered that one transmission couldn't handle the power of both engines. IF I could count on both transmissions to always shift into the same gear, and IF I didn't want the close ratio gears, I could do away with the differential. The differential is needed, if for nothing else, as a safety net for mis shifts.
    Last edited by KIRBY; 04-06-2020 at 02:19 PM.

  6. #86
    Moderator dirtdigger's Avatar
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    you want the power of two 750 engines just put one modern sport bike engine in it. Even a 600cc sport bike engine will get you 100hp plus 6speeds, water cooling and fuel injection.

  7. #87
    CB750 Guru amc49's Avatar
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    LOL, this one can't go there, it makes too much sense. He has the trickitis really bad.

  8. #88
    CB750 Enthusiast KIRBY's Avatar
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    I just want something unique, and I KNOW this will work. Wish I had the spar money to build it.

  9. #89
    CB750 Guru amc49's Avatar
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    If you knew the numbers of things I have thought up to never be built or made, the vast majority of them worked, but are they practical, the answer being no puts the idea out of my head. It working is not the only reason for a thing. It has to work to serve a positive useful purpose as well. When I worked on drag cars I came up with 10 ideas that worked out of the one that got used. I have worked out countless mods to carbs and head ports to constantly reject them for better ones. I have learned to reject a good idea while coming up with its' replacement.

    Where you are falling short, you are not reducing the fraction to a more useable basic number. Any 1100cc motor can easily do what you want and you don't need any double redundant trans with it. And then your power train needs no heavy electronic overhead and it is dead reliable. VERY valuable as most bikes run fine as is but they do NOT have any extra electrical resource to use for running add-on electronics. You still have not touched the most problematic part of your trike, the front end if it is not the driving end, you already have it super complicated because of that choice. How are you going to steer it?

    I too have had a creative urge and why I worked on the drag cars. I built an electronic ignition for my AMC back in the '70s as there was not one that worked for what I needed. The one I made ran to 9000 rpm with zero spark scatter and fired a .060" spark. Much of the AMC race cars we had to build as only Ford and Chevy really got nice parts made for them. I could build AMX cars that left the line so hard they pulled 6 foot wheelies with nothing expensive used as parts. Later after marriage I could not blow the big chunks of money on race stuff and have to not drive them either, family man now. How to deal with that urge? I turned it inside out and inward, deciding to use all skills for our own betterment and never looked back. I have never paid for any car or bike repair ever, I learn it when I don't know it. I can fix literally any part of a car or bike with zero issues when done. I stretched it further then to home repair and computers, learning with no training at all. To the point I never pay for anything other than the parts needed to do it and on the cars now I commonly fix the same broken part to not break again and used the same part over. Thus saving thousands and thousands of dollars that go directly into the family account.

    And that is in cars and bikes which I never had any formal training in. I worked as a lead pressman on hundred foot long printing presses and after 35 years of it came up with so many mods to save hundreds of thousands of $$$$$$, and now all that is pretty much wasted in retirement although the ideas can often fall into fields I may use myself.
    Last edited by amc49; 04-06-2020 at 04:11 PM.

  10. #90
    CB750 Enthusiast KIRBY's Avatar
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    Interesting history.Thanks. As for steering, the VW front end would work nicely.I don't plan a leaning trike. A car sized battery, chargeable at home, should take care of the electric servos for shift levers, and clutch. "Electric" not electronic. Your responses, and those from others, have been very helpful to me. I may never be able to afford to carry through with this, but it keeps my mind working (I'm 71), and I guess from your user name, that you are about that age. It IS a shame that AMC didn't survive. They had a lot of good ideas ahead of their time.

  11. #91
    CB750 Guru amc49's Avatar
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    Not electronic YET, your engine coupling idea would force you coming up with at least one engine ignition and timing unit since you likely lose it on one crank end. The electric servos will have at least one electronic controlled as it MUST activate and de-activate outside the operation of the other or the interference will tear transmission(s) up. The clutch MUST be dis-engaged throughout the entire shift or parts tear up. Simply hooking up both servos to the same wire to activate at the same time will buy you grief. You need clutch on, make the shift and clutch back off. All in milliseconds. So you will need exact timings there. As much as you do it (10 ratios) the two servos need to be linked to work as one unit. Meaning more electronics. Using SOHC for the engines will get you just enough charging to keep the engines going, DOHC used there will likely have trouble as they have trouble before you even think about adding a battery that size to keep up with. The rotors on them go out if you so much as spit on them.

    I am 66 years old FWIW.

  12. #92
    CB750 Enthusiast KIRBY's Avatar
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    The battery would not be recharged from the engines, but at home from a plug in battery charger.
    9 ratios, 1/1, 1/2, 2/2, 2/3, 3/3, 3/4, 4/4, 4/5, 5/5. Only one transmission shift at a time alternating.
    Left paddle shifter declutches and shifts only the left transmission.
    Right paddle shifter declutches and shifts only the right transmission.
    Either paddle cuts the coil power to both engines, eliminating the problem of one engine overrunning during shifts.
    To start off from a stop, a standard clutch peddle will operate both clutches, and bypass the coil cutoffs while the paddles are operated to put the two transmissions in first.
    Last edited by KIRBY; 04-07-2020 at 09:21 AM.

  13. #93
    CB750 Guru amc49's Avatar
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    'Left paddle shifter declutches and shifts only the left transmission.
    Right paddle shifter declutches and shifts only the right transmission.'

    That may well give trouble. Both actions of clutching and shifting at the exact same time using two servos can run into trouble, there is no guarantee the shift does not try to happen first and then possible torn up trans if the shifter servo applies too much force. Do it manually and you will see, if you do not get the shift right in the middle of clutch you miss or halfshift when the shift itself hangs up. A servo forcing things at that time can damage something. The ignition kill will help though, it unloads trans same way as the clutch does.

    The issue is that the gears are locked together on their sides by the undercut, either the clutch or kill allow them to unload to then move, the trans must be momentarily unloaded at the shift itself or you tear up the synchro dogs on gear sides that hold them in gear.

    Better if you can adjust the shifter servo pressure to be lighter, I used to be really good at speedshifting without ever rolling the gas off, you push down on the shifter lever and it does not shift until you wing the clutch to release the gear train. The shifts then are like an automatic trans. Quick.

    People who have dragged bikes with airshifters are the ones to talk to there.

    As to having to keep the contraption charged up at home........I have no use myself for something needing that, it must stay viable on its' own away from home or it has no real useability to me.
    It is not a successful invention if it is not standalone.

  14. #94
    CB750 Enthusiast KIRBY's Avatar
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    Quote Originally Posted by amc49 View Post
    Both actions of clutching and shifting at the exact same time using two servos can run into trouble,
    Yes, I can see that problem, IF I were to use one switch for both clutch AND shift, but I would mount the clutch and kill switches (separate) on the back of the paddle, so that I make them up with my finger on the way to pulling the paddle, and the shift switch on the wheel side of the paddle, so that it is made up after the paddle has been fully pulled. Thanks for bringing that up. I might have had to figure that out the hard way.
    Last edited by KIRBY; 04-07-2020 at 10:25 PM.

  15. #95
    CB750 Enthusiast KIRBY's Avatar
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    Quote Originally Posted by KIRBY View Post
    I can design it with spur gears. In fact, it would be easier. Round Bearing holes in the hub, but no bevel profile cutouts.
    After researching spur gear differentials, I'm going back to the bevel gear design. Easier to embed in a wheel hub. The spur gear design is far more complicated, and more gear teeth engaged. More friction.
    Last edited by KIRBY; 04-09-2020 at 03:02 PM.

  16. #96
    CB750 Guru amc49's Avatar
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    I've already explained to you once how your using the differential spiders far more than they ever get used in normal use means you likely NEED more gear engagement. If you wanted to truly lower friction and interference you would not have two powertrains engineered to interfere with each other to produce one output.

    You've missed the forest to focus on a small young sapling in this case. Using two transmissions (10+ gears in each) and then thinking like that is.....well, I don't think I need to go into it. Complicated? It's a bit too late to worry about that now in your design, you have buried yourself in it.

    It might interest you to read the history of the German Heinkel He 177 Greif bomber, Germany wanted a 4 engine bomber but decided instead to link two DB 600 series inline 12 cylinders together to act as one. To make a pair that only used the space of one cowling in a wing. The complexity lead to fails which lead to more complexity which lead to even more fails. The plane flew but never got the confidence of the aircrews as they broke down far more than they were ever shot down. The plane was a failure in complexity.
    Last edited by amc49; 04-10-2020 at 01:07 AM.

  17. #97
    CB750 Enthusiast KIRBY's Avatar
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    Quote Originally Posted by amc49 View Post
    If you wanted to truly lower friction and interference you would not have two powertrains engineered to interfere with each other to produce one output.
    Yes, there will be increased friction during intermediate gears, (1/2. etc) but those are only transitory. I would not cruise in intermediate gears. The increased friction I was referring to was six spur gear bearings,and six sets of spur gear teeth meshing against each other as well as with the side gears, as opposed to three bevel gear bearings, and three sets of bevel gear teeth meshing only with side gears.

    The interfering you mention is constructive interference, with the side in higher gear rolling the bevel gears and hub faster than the lower gear side.

  18. #98
    CB750 Guru amc49's Avatar
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    Constructive to what end? So you can run around the block three times to get the device up to speed when anybody else does it by the time they get to the next yard? You have never shifted that many gears, you will soon find yourself wishing you had never built it. Your trike would have to weight more than a truck to need that type of close geared transmission and use only a 30 hp. motor (which you are in essence reducing each motor to by hobbling them as you intend).

  19. #99
    CB750 Enthusiast KIRBY's Avatar
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    I still don't think you see what I see. We can go back and forth on this, but I really wanted to know if one transmission would handle both engines, and that was answered. Think I won't bother you guys anymore.

    Before I go:
    Assume a 134 HP, 88 Ft Lbs straight eight with two power take offs, one between cylinders 2 and 3, and one between cylinders 6 and 7. Power measured at either would be 134 HP and 88 Ft Lbs . . Hook both up to a common drive shaft, and the total power measured at the far end of the drive shaft will be 134 HP and 88 Ft Lbs. Cut that engine in half, connect them together with a Cush coupling, and you have two inline fours, each with 67 HP, and 44 Ft Lbs, but the two outputs connected to a common drive shaft will still total 134 HP and 88 Ft Lbs . The outputs do not fight each other. They add together. Take out the common drive shaft, and join the two outputs through a back driven differential, and the transmissions will split the total power in relation to the ratio of one gear to the other. Put the two transmissions in the same gears, and the split will be 50/50. Put one transmission in the next gear, and the split will asymmetrical, with more power going through one side than the other, but the total power on the differential will add up to the average between what it would be if both transmissions were in the same gear, and if both engines were in the next gear. The differential acts as an averager, not a subtractor. Shifting both transmissions together can be done, ignoring the four in between ratios, but those four would still be available if needed for quicker acceleration, or passing.
    Last edited by KIRBY; 04-10-2020 at 09:25 PM.

  20. #100
    CB750 Guru amc49's Avatar
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    Love you and no ill intention toward you at all. You will not get anywhere close to those power levels, you have added too many power killing features

    '...total power measured at the far end of the drive shaft will be 134 HP and 88 Ft Lbs.'

    Absolutely not. You are looking at 15%-20% loss by then on every engine on the planet.

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