Blue Dream: Maxarya Ray 2 Semi Recumbent w/high eff mid drive

[neptronix]

AW.. here's approximately what the back of those spiders looks like ( minus the crank arm )


The threaded hole is >= 11mm deep..
So to move the chainring outward 4-5mm, which would make it straight enough to clear the battery, a good chunk of metal needs to be removed from the 64 BCD bolt holes.



Another thought.. i have monster calves which tend to occasionally graze the chain..
Reducing the height of the chainline on the left side drive would help.

Currently i have a 46T going to a 24T chainring.
This could be a 42T to 20T.. or 38T to 20T and add 4T to the right drive side to compensate.

Looks like some options exist, but involve strategic filing:

 

[amberwolf]

While I was typing up the below, Papa made a much simpler and better suggestion.

___________________________

Ah, ok. So the goal is to "shorten" the inner ring of chainring bolt posts and associated structures so that chainring will sit farther outboard to move the chainline.

I suspect anything I can come up with to do what you're after will be more work than you have time for.

But one "easy" possibility (haha) is, for that specific spider design, to mount it on a motor-powered crankshaft (to save the work of handcranking it's rotation during the work), and then use a hand tool fixed to the same surface as the motor if possible, or handheld if not, to reduce the surface to the level required while the motor spins the spider past the tool. Sort of an improvised lathe.

 

[neptronix]

I don't trust shims for an additional ~4mm outwards. I have very strong legs.

AW, i did think about that, i don't have any way to affix a tool to the motor, and the distance is too short to use something like my dremel. The only thing i could fit in is a hand file. I don't feel confident that there wouldn't be collateral damage and the result would be flat.

I feel like a belt sander would be closer to the right way to do this, but.. i'd like as close to perfect flatness so that i don't compromise the mechanical bond i'm making with a shorter screw.

 

[amberwolf]

A belt sander doesn't make a flat surface unless you move it around a lot over a big area in the correct way--the belt itself shudders and vibrates and shimmies between the plate and the surface being sanded. (if you want flat wood, for instance, use a planer, not a sander).

A hand file (or rather, a rasp, given the amount to be removed) would do a better job if it is secured in position and the surface passed by it, but like lathing something down, the tool holder would have to move with it.

"perfect" flatness can be achieved with patience and fit-test-file-fit-file-fit-file, but it can take signficant time.... :/

 

[neptronix]

I want the most absolute flatness i can get because there is no spring loaded chain tensioner on the left side to soak up the side effects of any additional left-right motion. I would have to slacken the chain to counter that, which is bad.

A big flat sander is a problem because the square taper interface sticks out relative to the bolt holes.

I think some place that rebuilds small engines or such could figure out how to machine this properly. It's well worth doing correctly.

 

[amberwolf]

It's "easy" on a lathe, which is why that if I had to do it here, without using my lathe, I'd put the spider on a BB spindle, and spin that spindle, while using whatever tool to remove the material. Hand-holding the tool could get a very flat surface if enough patience and time were spent to get the technique right...but it would be "easier" if a tool support can be implemented. (but that's a lot of DIY and also time).

On a lathe, the tool would be affixed to the lathe bed, as is the motor support, so the tool stays in the same place relative to the lathed object (spider in this case), but is on a sliding holder that can be cranked toward the lathed object to keep removing more material while allowing the user to make the surfaces flat.


So any place that has a large enough lathe for the diameter of the spider will be able to do the work, if there's no crank arm to deal with.

 

[bananu7]

Perhaps an easier option would be to order a custom-made offset sprocket?

 

[neptronix]

AW: yeah, it sounds like this involves a lathe to get close enough to perfectly flat. I'm thinking a small engine repair shop would have such a thing. Does that sound right?

bananu: hmm, that would be difficult to do for such a small sprocket considering that the distance from sprocket teeth to the bolt holes holding it in is just millimeters. I think it would be easier to modify the gear carrier itself.

 

[amberwolf]

AW: yeah, it sounds like this involves a lathe to get close enough to perfectly flat. I'm thinking a small engine repair shop would have such a thing. Does that sound right?

They should, if they do their own work and don't farm it out. I imagine there are a number of things a lathe could do with engine parts, though I haven't ever worked on one in that way (I just replaced parts with new ones).

 

[neptronix]

Got the Uding H20 cargo fork in.

The good:
Fork height is +/-2mm vs the spinner grind fork.
6mm wider, which can be worked with since the widest part has a lot of extra meat.
Looks like it will take a 3.0" tire versus the max of 2.8" on the spinner grind.
The fork height could probably be reduced >10mm by cutting the legs ( good )
More than 10mm offset versus the spinner grind. Offset is within 5mm of the stock fork, that's great.

Stiction is worse though
The unit says it was made in 2023 and so we might have some sticky old oil in it. It was also shipped compressed and took a ton of pressure to expand, revealing that it was dry. Yet, when i removed air pressure, i got some lubricant spray, which tells me there is some lubrication inside. Maybe it needs a lot more.

I coated the stanchions with some new fork oil and it improved after many pumps. But still stickier than the spinner grind. hm.
Also, it only has 50mm of suspension instead of the promised 60mm
Maybe the seals will take a while to break in and i feel like i should give it some miles and maybe an internal cleanout before judging the stiction. The Spinner Grind i got was used, so may have been broken in.

I would say that for the purposes of using a larger tire ( this will improve suspension over imperfect surfaces which is my main problem ) and getting very close to a stock offset, the fork is a tiny bit over the threshold of worth trying.


I also called around some machine shops and was referred to an 85 year old local guy who is interested in taking the project of milling or lathe-ing down the crank spider. I just have to setup an appt with him. Booyah!

 

[bananu7]

Maybe the seals will take a while to break in

That is often the case and if it's a new fork it can be a good thing. If the legs themselves are straight and the bushings and seals aren't total crap, after it all beds in it should give you virtually no play which should in fact result in smoother operation than a loose rattly fork that's easy to press by hand but kinks in the bushings the moment side load from the frame head angle is applied.

In fact, in moto suspension, it's common to do an early first oil change to flush out the remainders of the break-in period.

If it's a budget fork and you feel that you want to invest in it, high quality seals thrown in then will almost always improve the situation.

 

[99t4]

What about storing it upside-down overnight to saturate the foam pads under the seals?

 

[neptronix]

These are great ideas. I'll give em a shot.

 

[neptronix]

Did some more measurements on the fork.

Uding H20 seems to be a couple mm less tall.. awesome.
With the 20 x 2.8" tire mounted.. i have 8mm of space on the extra sides, which is 0.3 inches. I 2x that to estimate how much extra tire i can stuff in.
That means my max should be a 20 x 3.4" tire

It's my intention to keep this frontend as low as feasibly possible, but i'm happy that i have some room to play with!

 

[neptronix]

Bad news:
This 130mm bottom bracket kit, on one of the cups, had the threaded part separate from the part you tension the BB with.

Good news:
New fork is installed and crank clearance doesn't look like an epic challenge.

I found 131 and 133mm bottom brackets on ebay from China. I can't believe what i paid for them. $78 shipped for two. These tariffs are kinda harsh!

 

[neptronix]

China BBs are in. Got some frickin' great news.

There is very minimal pedal -> fork interference with a 133mm BB. I could just remove meat from the cranks and get away with it.

Instead i would rather minimize the width and strategically shave metal off this fork too. This way, the 131mm BB works.
This way i'm only gaining 2mm width per side.

I think it's okay to compromise a tiny bit more on my insistence for a low Q factor. Because since this Mid drive has gone from 900w to 1600w, i shouldn't have to pedal too hard. I do hope this is not the point where my knees get pissed off though. Otherwise we gotta go back to the crappy fork.

should be able to reassemble and ride again soon.

 

[neptronix]

Howdy. Been too busy at my business to ride or play with ebikes until now.

I've been gradually shaving the cranks with a dremel grinding wheel and file.
The situation was a little worse than expected.

4mm total had to come off the sides of the cranks and 0.5mm had to come off the fork edges for clearance to happen.
I cannot take more off the edges of the cranks otherwise i will not have enough bolt surface to tighten/loosen the pedals, and in fact, they may be permanently stuck in there ( but that's OK )

I could take another 1mm off the edges of the forks, but the lighter weight of these forks with 30mm stanchions vs my previous 25mm stanchions makes me suspicious about the forks' strength.

Will test to see if my legs can tolerate 133mm in the next week ( i doubt it )
Because i have less crank, the worst case scenario is that i got back to the 25mm stanchion fork and have a 123mm or 125mm wide bottom bracket, which is what i know my legs like most.

More later!

 

[neptronix]

Good news.

Metal reductions come out to:
edge of fork: 1-2mm depending on spot
side of cranks: 2.25mm removed from inner

I'll admit.. this is cutting it a little close. I would have not removed this much metal if this wasn't a semi-recumbent ( super light front end, substantially lower pedal force possible )

Despite the lost metal, this is still huge step up in strength versus the spindly little thing the cannondale had ( plus that awful 16" wheel )



My legs seem to accept the 133mm bottom bracket, at least up the test hill.
My feet instinctively move inward as much as possible, to the point of touching the cranks.
And thanks to the super low offset big dog pedals, my feet can sit inwards to counter-correct the extra width.
These things were a serious win and i have 3 sets now.


I'll have to take it on a much longer course to see if pains develop or not.

Cornering wise, the extra 10mm of forward offset on the fork vs that spinner grind is a HUGE WIN at both high and low speeds for stability / steering confidence. It's starting to very much remind me of the cannondale.

Hamster pedaling at ~33mph, i didn't notice any major side to side wiggling. This might be because this fork is a bit less tall than what replaced it. This seems to have improved a tiny bit.

There is another 7mm of fork leg i could remove. I think it would be reasonable to remove half if possible and leave open the opportunity to go from 20 x 2.8" to 20 x 3.0".

Fork quality?

I doused the Uding fork's legs in some more oil before this ride and this fork still has mega stiction
I'm hoping that those bushings will eventually wear in.
I can tell the 20 x 2.8 tire on low pressure is doing a lot of the work on weaker bumps, so NVH is still okay.

Despite this, the frontend is still nice!

So far i am pleased. There's still a decent amount of room to improve comfort/handling. I'm starting to think 40mph is possible.. I'm taking it down a hill very fast as soon as possible before winter hits so i can gauge how close i am to that target.

 

[neptronix]

Interesting finding. Seat position 3, the most laid back, has improved enormously.

- The handlebars need to come in by ~2 inches. This problem can be fixed with taller cruiser handlebars. But it's tolerable for now.
- in this mode, the aerodynamic difference is large enough that i can be in 1 gear faster when pedaling.
- the bike is no longer a handful getting started from a stop in this position.
- doesn't seem rickety up to 32mph. Still wants to stay straight.



Awesome!

The next modifications are:
- longer handlebars
- move from 32T max rear cassette to 36T max so i can still climb on pedal power
- get crank spider machined -> finish lower battery mount.
- front wheel gets a 12mm wider rim

 

[Zambam]

What happened to the battery?

 

[neptronix]

The mount for the lower tube hasn't been created yet because i need to do some machining for clearance on the crank spider.
I needed to know what width bottom bracket i was going to end up with before creating that mount.

Just been using hills to help simulate speed to tune the handling

 

[neptronix]

Okay i figured out how to make an +5mm offset lower battery mount with some plate aluminum. It's more metal than i'd like but it will work.

Looks like next week we may have a little 50F weather.. so there's a chance to test the bike at high speed to see how the lower battery mount corners..

More to come..