Help needed for a Z cank ?

[stormbird]

Hi all
So currently weighing up options for my delta build.

1. mono boom frame
2. perimeter frame

Similar to this but with narrower part at the front [ top ] and not at the bottom [ back ] as shown

Currently 2) is winning because ?
a) unobstructed access to seat should I have to step over some body work ?
b) allow chain to run down side of trike , should be easier access to chain should it need working on ?
c) more frame to attach body work to ?

So I need to build some Z cranks ?

Like these , as I don't know which side of the frame I plan on running the chain down I have yet to decide how they will look ?

or

Problem 1]
One of the pedals needs to have 2 crank arms fastened to it and be wide enough to get my foot in ?
If 2 x BB's are used as shown the pedal must be able to be assembled AFTER the cranks are fitted else one of the BB axles will need to be removed to get it apart ?

If I use steel cranks I could drill out and sleeve the pedal threads for a M10 bolt and this is easily mounted using a single lock nut ?

Problem 2]
If I do the above how can I mount a pedal [ of some sort ] to rotate on the M10 bolt.

Problem 3]
Do the pedals need to be clip in types ?
Could they be a simple ali plate and say elastic strap for nose of shoe and lip on rear of shoe so normal shoes could be worn ?
Maybe something more like an exercise machine ?

maybe replace velcro strap with a elastic one ? these are on Aliexpress for under £10

Any ideas Paul

 

[maddox]

The combination of Delta and a Z crank seems weird tough. On the other hand, the floating camper delta did that way.

1: Steel or ali, as long you're not welding, it doesn't matter that much.

2: For pedal mounting. Pity you can't use a QR idea.

Point 3
I'm so used to my SPD's I would recommend those.

If you want to use straps and such, you'll have to think about the "vertical" plane too.

 

[stormbird]

The combination of Delta and a Z crank seems weird tough. On the other hand, the floating camper delta did that way.

It seems to be popular in Finland for some of their deltas , however the forces are great and when they stray away from pedal crank arms they do have failures

Point 3
I'm so used to my SPD's I would recommend those.

We tend to use those to stop wheel suck or in the case of the Python facilitate leg steering , neither should be required on this delta
One way could be mount some single sided SPD's on a plate mounted on a M10 pedal axle ?

If you want to use straps and such, you'll have to think about the "vertical" plane too.

The exercise pedals shown have a lip at the bottom for the heel.
To be honest it would be nice NOT to have to ride all the time with SPD's ?

Paul

 

[DannyC]

An interesting problem indeed.
Preventing the LH pedal shaft (as shown) from twisting/getting out of alignment may be difficult.
2 exact-match crank sets in steel with a solid round bar welded across the two inner arms and make your own pedal with split bearings (like con-rod bearings) under a custom/adapted pedal platform?
Effectively you are making your own crankshaft and the BB's are the "big-ends"

 

[stormbird]

An interesting problem indeed.
Preventing the LH pedal shaft (as shown) from twisting/getting out of alignment may be difficult.
2 exact-match crank sets in steel with a solid round bar welded across the two inner arms

If 2 x BB's are used as shown the pedal must be able to be assembled AFTER the cranks are fitted else one of the BB axles will need to be removed to get it apart ?

and make your own pedal with split bearings (like con-rod bearings) under a custom/adapted pedal platform?

What are they called ?

Looking at my 2 pair of singled sided SPD's I can see the SPD part simply screws into the pedal shell , so they could be unscrewed and used separately. However I wonder if unclipping from the pedal with 2 crank arms will be troublesome or maybe impossible in some pedal positions ?

I wonder if the pedal really needs to rotate much at all ? maybe a simple precision [ i/d bore tube ] rotating on a bolt would suffice ?

Paul

 

[DannyC]

If 2 x BB's are used as shown the pedal must be able to be assembled AFTER the cranks are fitted else one of the BB axles will need to be removed to get it apart ?

Yes, that's why you need to use split bearings and a carrier for them that the pedal platform mounts on so it can be put on that shaft section after assembly.

What are they called ?

"Split bearings", but you could use really cheap oilite press-in flanged bearings and cut them in half for this I think.

I wonder if the pedal really needs to rotate much at all ? maybe a simple precision [ i/d bore tube ] rotating on a bolt would suffice ?

You can check the rotation requirement by spot marking a pedal and the crank with a white line and see how far they move apart from each-other through a full rotation?
Probably could use just a bolt......as long as you can make the bolt rigidly secure from all movement at both ends across the pedal (which I think would be hard to do TBH), but you might find an easy way I have not thought of.

 

[stormbird]

I am at a loss to understand how this :-

2 exact-match crank sets in steel with a solid round bar welded across the two inner arms

Would NOT result in a pedal assembly that could only be removed by removing a BB axle first ?

What am I missing ?

Paul

 

[Popshot]

The pedals are the big ends, the BBs the mains.

With a multi piece system the issue will be to keep it aligned sufficiently under manufacturing so it rotates fully in the BBs. I'd mount the BBs first, preferably with a snug fitting tube inside both of them to aid alignment then build the central span in situ. That should guarantee it rotates. Another big issue is keeping the two pedals at the same height. One has a std mounting which will be very low in relation to the bearing. The one you make will need to be the same height. You could try adapting the existing pedal axle. If you take off the lock nut holding the pedal onto the axle and screw on a long nut instead that sticks out to at least the pedal edge you can then attach to the other crank arm with a bolt plus another lock nut against the long nut. This guarantees perfect pedal heights as neither is modified.

 

[stormbird]

Popshot

The problem with that approach is the pedal axles have a very [ very ] small thread at that end ?

possibly only M8 fine maybe even less ?

Paul

 

[Popshot]

True but all the force on the pedal is on the std pedal axle so no issue there. The issue will be on the transfer of that force to the drive side. Whether a high tensile bolt will transfer that or not I don't know though an honest guess would grant it's marginal at best. Logic would say to keep the long nut as long and the bolt as short as possible as a long nut will take more force. The bolt can be exceedingly short if the long nut goes right up to the drive crank. That would make the joint between the pedal axle and the long nut the weakest link IMO. Loctite red may help there. It does have the advantage of being relatively easy to make and try.

 

[stormbird]

The pedals are the big ends, the BBs the mains.

With a multi piece system the issue will be to keep it aligned sufficiently under manufacturing so it rotates fully in the BBs. I'd mount the BBs first, preferably with a snug fitting tube inside both of them to aid alignment then build the central span in situ. That should guarantee it rotates.

The plan was to get/make something snug fitted to help weld the middle bearing @ right angles to the main frame then as DannyC says make the other one bolt on with slotted holes , remembering Sandmans mantra ' if you can't make it accurate make it adjustable ? ' [ back to the snug tube again !]

Another big issue is keeping the two pedals at the same height. One has a std mounting which will be very low in relation to the bearing. The one you make will need to be the same height.

Not sure that will be much of an issue ? I remember DannyC angsting over something being out of true , I asked if he had run a tape measure over himself ?
Are feet are not the same size , our legs are not the same length with age our joins move out of line with each other the worlds full of close to symmetrical and does work ?

Paul

 

[Dale Rider]

It seems to be popular in Finland for some of their deltas , however the forces are great and when they stray away from pedal crank arms they do have failures

We tend to use those to stop wheel suck or in the case of the Python facilitate leg steering , neither should be required on this delta
One way could be mount some single sided SPD's on a plate mounted on a M10 pedal axle ?



The exercise pedals shown have a lip at the bottom for the heel.
To be honest it would be nice NOT to have to ride all the time with SPD's ?

Paul

Paul, that break looks like thin wall tube fracture.
Not a rugged solution. Think the square end of the crank is a stub axle stuffed in a tube, then in the pedestal bearing.
Not really a good way to do it. Any slight mis-alignment is going to play havoc on the weakest area.
So avoid solutions like that.

If I was making/designing this Z bender, I would:
Make, own BB with a common through bore. This would enable lining up with a long bar.
Use weldable steels, so up to EN8 (080M40) should be ok. To enable welding if needed.
Make own crank arms out of flat steel.
Possibly weld on bosses to bolt on pedals, (however?)
Possibly make own pedal shaft with brgs, to bolt (4xM6/M8) to crank arms.
Just off top of my head talk here.
BTW I have 3metres of 20mm EN8 in stock!
Some 20mm bore bearing spare too.
Just shout if you need some.

Martin

 

[DannyC]

I am at a loss to understand how this :-

2 exact-match crank sets in steel with a solid round bar welded across the two inner arms

Would NOT result in a pedal assembly that could only be removed by removing a BB axle first ?

What am I missing ?

Paul

Not missing anything, how many times do you think you will be popping it in and out? Daily, or once in a blue moon?

 

[stormbird]

Not missing anything, how many times do you think you will be popping it in and out? Daily, or once in a blue moon?

I gave away a 2 wheel lwb I was building because the fork and head tube/set was from an old Raleigh and I could not find a pair of caged bearings that fit the steerer , whilst building something things go together and come apart loads of times and if taking it apart becomes a struggle then it's appeal soon wears thin [ in my world YMMV ? ]

Paul

 

[stormbird]

So this might work

The piece between the pedal cranks will be based on M12 threaded rod the hex couplers can be wound out to take up a small amount of slack and the couples are captured from the outside by short M12 bolts.
The pedal will be mounted on the M12 precision tubing rotating on the M12 thread , it may be prudent to leave room for 2 lock nuts between the precision tube and the hex couplers.
I was hoping the M12 bots in M14 pedal holes would give a little bit of wiggle room if needed ?
If it works loose maybe go up to M14 ?

If the whole lot seems to work maybe it would be sensible to Loctite it when in use ?

Paul

 

[Popshot]

Any system only needs to be dismantlable at one side at the most. The more places it has to fasten the more places it can come loose.

 

[DannyC]

Sorry, I really think that will fall apart every 5 minutes or at the most inconvenient moment (whichever is the most annoying).
And if you Loctite it to try to prevent failure how will you disassemble it if you really need to?
Heat can be used to break Loctite bonds, but would that not be a bit risky to the rest of the vehicle?
Good Luck.

 

[stormbird]

Any system only needs to be dismantlable at one side at the most. The more places it has to fasten the more places it can come loose.

Good point it just looked better symmetrical , of course the threaded rod could be a fully threaded bolt and lock nutted tight to one pedal arm after stuff is threaded on it [ I hope ]

Paul

 

[jonrev]

Paul I suspect you have probably discounted this setup but it was how I had imagined doing it so thought I'd just put it here for your perusal.

The main structure is some 1" (probably?) thick walled tube for the outer pieces and a couple of the old style cottared crank arms cut down and welded together via a piece of tube. I hadn't actually thought of using a center bottom bracket at the time.
The two crank arms would be used the wrong way round so the larger ends would be the pedal ends and would be fixed to pieces of BB shafts to form the pedal shafts or to newly made susbstitute shafts if the originals were not long enough (I hadn't thought that far ahead). These would be welded to the tubes of the main structure.
I had thought the pedals themselves could be plates of some kind welded to pieces of tube (or some turned items). The tube would run on needle roller bearings on the pedal shaft. I have no idea if such bearings are available but 'Bearingboys' have a great selection of various bearing types so maybe? Last resort would be oilite bushes but they could have a pretty hard life in this application I should think.

Anyway that's how far I'd got with my thinking so maybe there's something there that might spark an idea for you. Really looking forward to watching your build.

John

 

[DannyC]

Paul I suspect you have probably discounted this setup but it was how I had imagined doing it so thought I'd just put it here for your perusal.

The main structure is some 1" (probably?) thick walled tube for the outer pieces and a couple of the old style cottared crank arms cut down and welded together via a piece of tube. I hadn't actually thought of using a center bottom bracket at the time.
The two crank arms would be used the wrong way round so the larger ends would be the pedal ends and would be fixed to pieces of BB shafts to form the pedal shafts or to newly made susbstitute shafts if the originals were not long enough (I hadn't thought that far ahead). These would be welded to the tubes of the main structure.
I had thought the pedals themselves could be plates of some kind welded to pieces of tube (or some turned items). The tube would run on needle roller bearings on the pedal shaft. I have no idea if such bearings are available but 'Bearingboys' have a great selection of various bearing types so maybe? Last resort would be oilite bushes but they could have a pretty hard life in this application I should think.

Anyway that's how far I'd got with my thinking so maybe there's something there that might spark an idea for you. Really looking forward to watching your build.

John

Yes, that's aligned with what I was suggesting John. But to keep it within what Paul has available I was thinking to use standard steel pedal cranks and your illustration of the pedal platform for the left pedal but maybe a standard pedal for the right hand one.