My 3x3 Recumbent off-road trike

Discussion in 'Other Toys/Hobbies' started by Sam_Q, May 5, 2010.

  1. OP
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    Sam_Q

    Sam_Q Member

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    Almost completely finished my center power transfer shaft, with it being such a complex part I am really glad I didn't make enough critical mistakes that I had to redo it. Here's how it looks now:

    [​IMG]

    The flat sides in the middle suit a 22mm spanner to help with dissassembly. I still need to remove the small shoulder on the right middle, otherwise it's complete.



    [​IMG]

    View from the end, I took this metal out to save weight as it wasn't needed.



    [​IMG]

    Looking inside, there's a 25mm long straight section that's machined to be exactly 20mm before coming to a 20 x 1.5 L.H thread. The uni joint & outer bearing support shaft will locate on this section and transmit the torque using this internal thread.



    The sprocket cluster wound on:

    [​IMG]



    and in place on the frame:

    [​IMG]

    Notice how the main spine and crank boom are misaligned, this is how it's meant to sit. I purposefully offset the crank shell 3mm off to one side, that added to the ftattened section and the different in pipe sizes adds to the illusion of being way out of alignment.
     
  2. OP
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    Sam_Q

    Sam_Q Member

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    How the frame is looking at the moment:

    [​IMG]
     
  3. OP
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    Sam_Q

    Sam_Q Member

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    I started and finished a small but important part today. Unfortunetly I had to do it twice as I wasn't far from finishing the first go when I realised I was cutting an internal right hand thread when I needed a left. After a bit of a mini tantrum, food and rest I went back to it and made the final one. Here it is below- a simple adapter:

    [​IMG]

    Features an (M22 x 1) L.H internal thread and a (M30 x 1) right hand thread on the outside.



    [​IMG]

    My drive-line parts that I have so far laid out. The next series of photos below show the order in which this is assembled.



    [​IMG]

    Central shaft in place with the adapter wound into the freewheel.



    [​IMG]

    Adapter wound on.



    [​IMG]

    Sprocket adapter put on to the freewheel. I still need to make the coupling that clamps to the other side of the teeth.



    How the frame looks now shown below, I slid on a prototype uni-joint for the visual. I think it's looking quite aggressive.

    [​IMG]

    [​IMG]


    The next part I need to make to continue with this center drive is the shaft that fits through the middle of the gear cluster. However this is a bit of an issue for me as ideally I should be making it one piece with the uni-joint. However I am far from ready with my uni-joint design. I could make another thread in there which would get me going in rear wheel drive and let the uni-joint be independantly changed but I would be compromising the design. The main thing however would be that I could make the shaft and continue with the rest of the construction. It also has the advantage making it likely I am able to make this shaft without making ireversable mistake because it's only a basic design without the complex uni-joint machining involved, this alone movitates me to make them seperate.
     
  4. Quan-Time

    Quan-Time Member

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    Wow, starting to look like something now. Im really liking it.

    The rear red chain tensioner (?), whats that about ? Or is it just a guide roller for the chain to stop excessive chain slap ?
     
  5. OP
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    Sam_Q

    Sam_Q Member

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    Yes it's starting to be recognisable.

    The two pulleys are for the return chain routing. The chain runs over the fork, around the top of the rear pulley, under the middle pulley and then past the inside of the tension pulley to the cog. This allows every part of the chain to be higher than the bottom side of the frame which will have a solid bash gaurd on it. If I get something usable in the end I am going to give it such a beating
     
  6. OP
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    Sam_Q

    Sam_Q Member

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    Machining took way too long today for something simple looking, but I guess that's how this hobby works. Rush a little bit and the part ends up in the bin. Time aside 38mm solid cro-mo isn't cheap either.

    Here's what I did:



    [​IMG]

    It's the part on the top right, it still needs the middle machined out and another fine + left hand thread cut on the inside to let the uni-joint wind in.



    [​IMG]

    It fit's into my main shaft as so, this is just for the photo and without the other parts in place.


    [​IMG]

    Assembled together with the cluster, 15T fixed cog and the thin-section bearing. This particular bearing is an odd size at 35-42-5 which most bearing places wouldn't even have a listing for in their books. However it's an ideal size for my application. The cog tightens against the fixed shoulder of the bearing until it's pushed against the shoulder.

    I will have a bracket that comes off the main boom for the third bearing support, this will also be my deraileur mount. I also plan on putting some flats into the outer shoulder to help me take it apart for servicing. I want good access to every bearing or servicable part on this trike.

    What's good about this driveline arangement is that I can run it in rear wheel drive independently. This is because the uni-joints don't need to be attached for the rear wheel to still get it's power. My initial design had the bearing support and rear cog on the outside of the uni-joint itself.
     
    Last edited: Jun 17, 2012
  7. OP
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    Sam_Q

    Sam_Q Member

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    A very notable update today. I have just finished a 40 hour training course with Solidworks CAD software. I have not had much time yet but here is one of the things I have have come up with so far- it's a high angle uni-joint:

    [​IMG]

    [​IMG]

    I started off with a very basic design from which I optimised it to be able to tilt to a theoretical 50 degree angle before binding, followed by bringing the material closer to the pivots where possible to increase strength and reduce size and then finally started to sculpt bits out to reduce weight.


    I also am able to do basic Von Mises Stress testing:

    [​IMG]

    This is with the inside base as a fixed point and 1000Nm each into the two pivots pushing in opposite directions. It still came up with a 5 fold factor of safety with 4130 and the weight was 70 grams.

    When I did do this work I do however only make changes that I would be able to do on my mill, I would of loved to of sculpted curved variable depth sections out but I am not going to pay someone to CNC machine this for me.

    This still didn't have some of the exact dimensions and I needed a design for a 30mm shaft input unlike this 22mm input. That one while finished doesn't look quite as interesting but it is more accurate of what I would like to do. I will post a picture of that soon.


    Here's something else I came up with, it's a mountain tamer alternative:

    [​IMG]


    This update means that from here on things change significantly, I am likely going to digitize almost all of the parts before I make them and possibly do a model of the whole frame design. I was shown how to do moveable assemblies so I could add a theoretical motor to provide a turning force to the crank and show a video of everything being powered.

    Previously I had given up trying to model a uni-joint, hence why I made a couple of prototypes. Even looking at those I struggled to visualise the changes that where necessary to make them be able to turn to a greater angle. Now with only a few hours of computer work I have a design that can tilt even beyond what I thought I could do with an offset pivot spider. The alternative would of been an obscene amount of trial and error uni's which realistically would of made me just compromise in the end and also resort to a high offset spider which would of caused much more drag.

    So from now one there's going to be a big pile of CAD drawings on here, well on the bright side people will finally be able to see where I am heading.
     
  8. aznpsuazn

    aznpsuazn Member

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    I think you should start building motorbikes :thumbup:
     
  9. Anakist

    Anakist Member

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    Looking amazing!

    I have just started learning to turn. I am impressed by your surface finish! Mine always looks like it is dragging but the guy teaching me says it is fine for that material on that lathe.

    James
     
  10. OP
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    Sam_Q

    Sam_Q Member

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    James are you working with black (mild) steel? My parts above normally would have a shocking surface finish and I have some special tips that help but for anything that has a bearing go down it I do something very odd to get that finish. I use a parting blade as a sideways turning tool. I get it within 0.1mm then I run the parting tool down it. It's wrong in every way however I don't have anything that gives a nicer finish on cro-mo and the side load doesn't seem to bother it. Just don't try it ok!!

    For the black metal a buddy of mine is getting outstanding results with Cermet tips and very high speeds.

    Anyway my point of all this is to say that there seems to be an endless amount of tricks and tungsten tips available so don't concern yourself too much at this stage. Later you can try different tooling to have a nicer finish.




    I was looking back at the start of this thread and I found it's amazing that in such a time ago I had little idea on how to do things. Sure I am still clueless most of the time but it's been one serious learning curve.
     
    Last edited: Jun 29, 2012
  11. Anakist

    Anakist Member

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    Most of what I am playing with is 4140 IIRC. The guy I am learning in doesn't do a lot of turning so he only has basic tips. I am not worried about getting mirror finish at the moment. Much more interested in learning as much as I can as fast as I can (I do it after hours away in the town I am working in. Don't know how much longer I have wit this contract) and I can perfect it all later.

    I have noticed how nice the finish is from the parting tool. Awesome lateral thinking!

    James
     
  12. OP
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    Sam_Q

    Sam_Q Member

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    The finish of the parting tool is a quirk of the cutter angle, if I where to source a tip for my normal turning holder with the same angles and reliefs then it should work just as well.

    Sounds like your on the right track anyway, learning what you can while you can is smart thinking. 4140 will leave lots of drag marks and spots so don't expect much out of it.

    It's a pity your not a local
     
  13. Liighthead

    Liighthead New Member

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    very well done sir. :D

    subbing in to see how you go looks soild though :Pirate:
     
  14. OP
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    Sam_Q

    Sam_Q Member

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    thanks I guess I should give an update:

    I have not been posting anything because I have bought a new milling machine, taken the engine out of my car and am behind in my parts stockpile for my business.

    Also I have a friend who has been setting up his own CNC mill which he is still working out and I hope to get some of my parts made there. If things work out I will convert my existing machine to CNC operations also.
     
  15. OP
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    Sam_Q

    Sam_Q Member

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    I have not done any sort of meaningfull update for some time and I only have a small update today. However a lot is being organised at the moment in regard to equipment and concepts so it will be a little while yet before I have something really worth looking at.

    Today all I have to show is me testing a concept. I wanted to know if I could with a rotating table cut a Shimano cassette compatiable spline. I tried this on some scrap metal and the answer is yes:

    [​IMG]

    [​IMG]

    it fits nicer than the photo suggests.

    What this does it let me make a design that is much nicer than what I have with an even wider range of ratios.

    My idea for gearing is a 14/28T combo on the front and a 28 to 9Tooth on the cluster in the middle. It has it's perks of not having many of the normal limitations in the way. I could even fit an 8 tooth cog if I really wanted to.

    Topping out at 62 gear inches is no problem for me as I won't do that sort of riding.
     
  16. OP
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    Sam_Q

    Sam_Q Member

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    it's been a long time again. Right now I am upgrading my workshop and have been trying to get some stock out the way with my business. However I have been spending more time in CAD than anything else really.

    So anyway to progress I wanted to do a real world test on this uni-joint design that I designed previously:

    [​IMG]

    So I did the same thing as last time, made one out of HDPE and kept loading it up till it could not handle any more torque. Here is the assembly ready to be tortured

    [​IMG]

    Using my torque wrench I managed to get to 35LB/f before it reached it's elastic limit. I hoped for 50NM and I got 48 so I am pretty happy with that. I want to have a 200 to 300NM capability, and when I make these out of cro-mo I doubt that it won't be a problem at all. Also it deformed exactly as solidworks predicted it would, handy.


    Here is the cad model of the frame assembly so far:

    [​IMG]

    [​IMG]

    I high-jacked all the main cogs from GrabCAD but I made a crude 14T cog and the everything else myself.

    Next up is another stress test for a spline type concept.
     
  17. OP
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    Sam_Q

    Sam_Q Member

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    I noticed I never showed my new front hub that I made a little while ago. I had a pretty serious breakthrough in my front end design a little while ago thanks to some helpful hints from a guy on another forum.

    Blank materials below, the block was made into a spindle housing but I didn't like how it was turning out so I decided against continuing with it.

    [​IMG]


    Skipping every step for the final hub, as a reference the larger flange is 100mm (4"), it's a big diameter hub.

    [​IMG]

    [​IMG]

    [​IMG]

    This shows the inside and where the sneaky design features come in:

    - It has a bell shape that leads to the inner spoke holes to allow part of the hub to overhang the actual spindle housing. This allows the edge of the hub to be just off the kingpin tube. The result is about a reduction in the front track of 50mm overall/25mm per side. Also this does a very good job of compensating for the scrub radius geometry and I only need a gentle angle on the kingpin because of it.

    - The first ridge in the back is for a seriously expensive 35-47-7 bearing. This fits right over part of the uni joint itself to shorten the axle significantly. This then lets the line of the king-pin intersect right through the middle of the uni-joint so there is a negligible change in axle length when turning. This is the most critical reason for updating my design.

    - The metal ring inside is taken from a BMX hub and is called a ratchet ring. It's part of a freewheel mechanism which will be between this ring and some pawls that located on the axle itself. With these parts I will have a freewheeling mechanism built into hub itself between the bearings. There will be no visible sign at all from the outside how I have this so it might confuse some people! Doing it this way means a stupidly tough design, uses off the shelf bits, light, no additional space use at all and not too bad to machine up.

    - The outer bearing is a 20mm I.D so smaller than the cuts needed for the freewheel pawls, it will also have either a small lock-nut or an internal thread in the end of the axle for a locking bolt instead. I will likely go for the later as I can put more torque into it for protruding space and I don't have to worry about a narrow thread stripping.

    All I need to do to finish this hub off is a small spacer behind the ratchet ring and a cone shape on the other side. Because of tooling limitations I can't cut a blind thread right up to a shoulder. So having a small spacer will stop the ring jamming hard off the end of the thread. As for the cone spacer on the other side it will push the freewheel pawls back in when I slide the wheel off. Otherwise the pawls would pop out once past the bearing and lock in making wheel removal no longer a practical option.

    I have spent many hours designing and working on this solving many problems. The result should be a light front end that's seriously compact and tough. I am hoping that with my extensive use of CAD I will seriously reduce the amount of parts I make to later discard.
     
  18. admiralranga

    admiralranga Member

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    UPDATE TIME!, nice work there it looks impressive. I can't wait to see everything put together.
     
  19. brayway

    brayway Member

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    Wow, that's some impressive work there! :eek:
     
  20. OP
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    Sam_Q

    Sam_Q Member

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    I didn't get to finish my update yesterday because I ran out of time. So here is part 2:

    For the continuation of my uni-joint design I wanted to see how much drag there is from using push in sleeves over needle bearings and also what happens when they reach the extreme end of the angle. Is it possible to have a uni-joint that can go to 50 degrees and still turn?

    So to find these things out I started to make a complete uni-joint. I decided to replicated the front outside design but in aluminium instead of ease of machining.

    The starting point- the starting points for these yokes are out of a block of 40mm

    [​IMG]


    I started off milling upright for the first yoke, this later proved to be a worse option that doing everything on the side:

    [​IMG]


    Skipping a few steps with the basic shape, notice the yoke on the left has a bearing shoulder built into it. This will be for the 35mm bearing that goes into the hub to save space. This yoke will be an integral part of the axle in it's final version.

    [​IMG]


    The inside tappered by hand with a die grinder. This proved to not be enough and I will be putting this on my tilting table at 45 degrees to make further cuts:

    [​IMG]



    Now the tricky part, I wanted to be able to do real world testing on these so I needed a test rig. Something that could hold the uni-joint in place but be able to change the angle as I saw fit. A small turn handle could rotate the unit and with bearing supports to make it run true.

    Here is the partially complete rig:

    [​IMG]

    The rod end needs to be spaced up to line up in the same plane and I wish to engrave increments to show the angle it's set at.

    At the fixed end I put a double 12mm bearing in, this will have the turn handle.

    Now I need to cut the threads into the shaft, make the spacer for behind the first yoke and actually finish my uni-joint off to put it into this. I am quite curious on how it will be when it comes together. Assuming it actually works I shall post a video of it turning when I am ready.
     

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