MP6 2.0: pivot jackshaft

[panurge]

A thread to discuss about the best way to turn my MP6 LHDrive Astro-bike (http://endless-sphere.com/forums/viewtopic.php?f=6&t=50842#p754599) into a concentric pivot jackshaft drive, but also to speak about any concentric setups done or doable....

I have been speculating longtime about how to combine the pedal and the motor inputs in a single final transmission via a concentric pivot shaft, with a dedicated frame from scratch, it could be done. Indeed that's my final objective....
But After riding my bike for 2000km I know now, that I do not need a combined final transmission, and a 9 speed cluster could be a problem more than a plus for the motor (well, a 2speed gearbox would be great :wink: ), but a pivot jackshaft for the motor only, keeping the motor line independent, as is right now, should be a crucial step forward.

The best thing to have would be a custom rear hub with a left freewheel/rotor mount, of course, but since this is actually far from being real, I need a freewheeling system at the jackshaft level... I see 2 ways to achieve this feature on my bike with "minimal" mods...
A picture worth thousands words so that's a preliminary assemblage to check lines and spaces for option 1:
...that's the plan 1:

- Extend the 20mm hollow (7075) axle on my pivot,

- Fit around it a short custom machined freehub body, with a pair of ball bearings inside for the protruded axle, and maybe a couple of thrusts at the ends... (a tiny assembly could include 2x 6704 and 2xAXK2035 needle thrusts).

- flat-out a 4mm thick 35mm Dia circle from the outer surface of the actual 15mm pivotCNC swingarm's plate around the pivot bore, that's to gain some room for a proper line and create also the housing for the eventual needle thrust. (since I have a pair of spare swingarms for this bike, I have no fear trying to slightly mod this one, with the risk of fail).

- add by weld or by interference/epoxy, a second external thin plate (I have the 1"1/8ID bridge pipe and the stay as support for the weld or epoxy): it will support the axle end, and allow to complete the sandwich with an end bolt, just like is now, and would accommodate the other thrust if needed.

Plan 2 is to make a new hollow steel axle always 20mm OD but with M17 or M18 female threads for the end bolt instead of the actual M16 to gain internal diameter space for a pass thru jackshaft of 1/2", this one would turn on 1/2" id ball bearings placed in special custom Bolt-Caps, a sort of miniature Ext.Bearing BB cup, you could see some sketches of the concept into the old thread here http://endless-sphere.com/forums/viewtopic.php?f=28&t=25101&start=100#p673292

What do you say guys?, Since I'm pretty new about projecting a transmission for Kwatts inputs, any comment about these solutions and to any other systems are welcome...
Finally, some additional picture of the Shimano compatible freewheel from Crewkerz and the freehub body I could use for the assembly.

 

[drewjet]

Cool ideas. Where did you find that freewheel?

 

[yawstick]

I'm not sure I'm following everything you are trying to do and I've not looked at your other threads yet but.... could you not move the primary jack shaft on your astro drive. Let it drive through a shaft through your rear end pivot and eliminate a lot of parts.... just a thought.
Wicked looking machine by the way.

 

[spinningmagnets]

I am curious also about the splined freewheel. The spline anodization makes it look like a factory item. Luke and Thud went to great lengths to make splined freewheels available to ES members a while back, and everyone was hoping that someday they could be purchased off-the-shelf. Do you have a link?

 

[panurge]

Cool ideas. Where did you find that freewheel?

Hello drewjet
It comes from Crewkerz, that's a young french trial-bike brand, they have on their line trial frames with a slightly modded PF30 BottomBracket (called AF30) with IHG splines on the RH crankshaft's end and this 18t splined freewheel instead of the usual Sq. or ISIS crankarm with BSA threads for a stand-alone freewheel....

I am curious also about the splined freewheel. The spline anodization makes it look like a factory item. Luke and Thud went to great lengths to make splined freewheels available to ES members a while back, and everyone was hoping that someday they could be purchased off-the-shelf. Do you have a link?

Hi spinningmagnets
Have not yet deeply investigated about the real source of this freewheel (I mean the factory or the country of origin), I just got it to satisfy my curiosity, indeed I asked for the whole crankset, but actually could be bought only with a complete 2013 frame (they have few remaining complete bikes at good discount prices).
The actual BB could not fit a standard PF30 without mods but the 2014 crankset should fit standard....(so we will have hopefully, a new high end option for freewheeling crankdrives into PF30 Bikes. do not know the spindle length, though.
To purchase it just contact them via their website, they have been really kind with me...http://www.crewkerzstore.com/contact-crewkerz.htm
The unit seems to be a standard 108.9 trial freewheel so noticeable drag and superfast engage, the anodize is not top quality...definitively it is not comparable to an ENO trials, but compared to a dicta or similar is a piece of art. the splines are really precise and tight fit, that's good...

I'm not sure I'm following everything you are trying to do and I've not looked at your other threads yet but.... could you not move the primary jack shaft on your astro drive. Let it drive through a shaft through your rear end pivot and eliminate a lot of parts.... just a thought.
Wicked looking machine by the way.

I understand, My English is terrible and the post is long....Anyway that's a good point in theory since the second stage would be a little 18:15 in my plan 1....but the 80t pulley+torque limiter at the pivot, leads to at least 4 big problems:
- too wide, it will heat the crankarm
- too big in diameter with more clearance hassles (there's still a chainring, right side :wink: )
- possible issues with the primary belt alignment because of the drive and driven pulleys wouldn't be absolutely solid as is in Matt's drives, especially if you consider to use the bike on trails....
- looks ugly :wink:

BTW with a RH setup where pedal and motor drives reach independently the wheel on the right, a pivot drive setup with a single stage as per your suggestion is more realistic. It should be perfect and easy for a non pedal setup, mmmh, I wanna try it sometimes .....

 

[Miles]

Hi Jules,

The freewheel looks to be from the same factory as my Monty freewheel. The anodising on that is crap, too...

What is the ID of the hollow axle?

 

[panurge]

Hi Miles
The actual hollow axle is 7075alloy, 20mmOD and M16x1.5 thread ID (so a 14mm available ID). It was almost impossible while modeling with M16, to find a working configuration even for a 12mm pass-thru jackshaft, only for a 10mm one is a quiet easy mod....the main problem is the Bearing-Cup-bolt wall thickness....

That's a List of the other options I'm trying to figure out:

- Change the material for steel or Ti and make an M17 thread to gain 1mm, still tight for an 1/2" maybe good for a 12mm Jackshaft.

- Make the axle with external M20 threaded ends and than make the bearing housing into a big nut instead of a bolt, this would solve most issues and allows for a bigger Jackshaft (15mm )

- Make a bigger Hollow Axle and go with the internal threads again: In fact having a 2.5mm thick bushing assembly for the pivot's bearings

I actually may increase the axle to 22mm (1.5mm bushings) or to a direct bearing contact (25x37 actually, but without the sleeve a 24x37 enduro could be better) this would involve to modify the pivot assembly (internal spacer) and to enlarge the bores onto the swingarm's plates....though

If you have some ideas, this would be great, Miles, what do you think about the Mini Jackshaft approach with that splined body? Is that feasible? does it make sense with the tiny bearing setup I've mentioned? what about using Needle thrusts?

Cheers

 

[Miles]

Could you use a 17mm dia. stub axle extension, for option 1? It would give you a better choice of bearings.

 

[panurge]

yes, that's a good option, but need a smaller end bolt. This stub, if screwed-on, and machined with a proper flange between the threads and the blank section, could act also as lock bolt for the pivot assembly. than, maybe, the thrust bearings are redundant.
With the motor drive only, going to this jackshaft, I should expect around 1300 max rpm and max 40Nm of torque...that's with 5:1+18:15 and a 7 Nm max output of the 3220. Have you a source for bearing's load ratings?

Yes the freewheel looks like a monty or a viz or other similar trials units...seems they all comes from the same factory, maybe at Crewkerz they make only the splined inner for it....maybe not even that.

 

[Miles]

Other possibilities:

http://simplybearings.co.uk/shop/p150721/3803B2RSRTVH+Rubber+Sealed+Double+Row+Angular+Contact+Ball+Bearing+17x26x7mm/product_info.html

http://simplybearings.co.uk/shop/advanced_search_result.php?categories_id=31&1_10=9715_1&21_210=9715_21&22_220=9715_22&23_230=9715_23&x=0&y=0&extra_field_filter=1

 

[Miles]

Have you a source for bearing's load ratings?

6704 (20x27x4) Cr (dynamic radial load) is 1040 Newtons
68032 (17x26x7) Cr is 2200 Newtons
380382 (17x26x7, double row) Cr is 2480 Newtons

So, definitely worth changing to 17mm shaft....

Contact angle on the double row bearings is 25 degrees.

 

[Miles]

2015 (20x27x15, needle roller) Cr is 10400 Newtons

 

[panurge]

Hello Miles

The double row is a good option as the needle roller one...17mm gives really more choices...
Thanks a lot for the ratings.
I'm thinking about how to effectively lock the pivoting axle, if at the end of the protruding axle/stub, or with an external thread+nut/flange facing the original swingarm plate as is now...

 

[Miles]

I think we should start modelling it up, at this stage....

How long is the existing axle?

 

[panurge]

I'm really busy these days at work and with the family., so not a lot of time for cad....anyway, the existing 20mm axle is 83mm long, M16x1.5 internal threads are extended for 20mm each side
The overall width is 88 (side to side without bolts) composed by: 2x15mm (swingarm) + 2x3.5mm (bearings assembly)+ 51mm (frame width).

Today, My buddy at the motor-workshop says: " hey but why don't you simply wrap the top of the actual chain around a solid idler in this stub? you get the same result in term of chain action, in less room, and avoiding to make another stage with no significant reduction.....
Damn, he is not that wrong.....But this way I couldn't go to the next step on the plan :wink: because the chain length would be anyway too long...
The preferential way still remains the pass thru jackshaft, indeed....it has some advantages:
- thinner assembly (since input /output are at the opposites)
- possibly a better look
- the assembly could be used with minimal mods for combining the pedal and motor inputs.
- a pass thru without major swingarm or frame mods allows the system to be used on any of the OLD or New Onion FS frames that share the same pivoting scheme...
However, the stub/protruding option could be cheaper and easier.

 

[Miles]

I'm really busy these days at work and with the family., so not a lot of time for cad....anyway, the existing 20mm axle is 83mm long, M16x1.5 internal threads are extended for 20mm each side
The overall width is 88 (side to side without bolts) composed by: 2x15mm (swingarm) + 2x3.5mm (bearings assembly)+ 51mm (frame width).

Yes, I was offering to....

 

[panurge]

Wow, that's more than I would ask, mate, but if you have some time for this, how could I refuse this offer? 8) no doubt that with your modeling skills that wouldn't take more than few minutes.. :wink: ..helping the thread to become more clear for all...and me to better visualize the ensemble.
As you can see from numbers, the more problematic thing is the chainline, the actual chainline (135mm rear) is 40mm, so it pass just under the pivot. but I have another swingarm with 150mm dropouts that's a 7.5mm gain each side. this is anyway far from the 55mm ideal chainline that I need for the drive sprocket at the pivot level, or 57+, with the centertrack pulley I'm planning to use. So, Basically I need 7-10mm gain left side at the wheel hub. Actually I have 6mm between the rear 61t sprocket and the calliper to play with, still need another 3-5mm, this could be achieved only with a custom wheel or thinning the swingarm plate as figured out before.

 

[panurge]

I've found that using a brocken aero carbon leg from an RR fork, and some spare parts I've on the shelf, I can figure out, and even try with some care the simple driver idler option....no times now to reverse the motor drive mount to align the ENO like in the previous picture, but I know that chainline is good enough.....
Could make same thing right side for pedals, too so 2 separated drive both with drive pivot idler, but maybe the derailing 9 speed chain wouldn't likes this...
Also trying to figure out a shape for a composite cover for winter rides

 

[panurge]

ok, found the time :wink:

The carbon leg could be replaced by a plate with a welded 1-1/8" od stub (a steerer slice seems perfect) to insert it into the swingarm's "bridge" 1-1/8" id pipe (with glue or some sort of expander from the other side...)

 

[panurge]

In Italy we say: Buona fine e miglior principio!!!
to all you guys:
Happy year end and a better starting new one!!!!

Cheers