LightningRods mid drive kit

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
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izeman
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Re: LightningRods mid drive kit

Post by izeman » Oct 07, 2017 4:01 am

john it's not about: will it break or not, it's about doing it right or not.
screws are just not made for what they are used here. they are there to clamp parts together primarily and not for shearing forces (though they can take some of course)

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Re: LightningRods mid drive kit

Post by SlowCo » Oct 07, 2017 12:14 pm

izeman wrote:john it's not about: will it break or not, it's about doing it right or not.
screws are just not made for what they are used here. they are there to clamp parts together primarily and not for shearing forces (though they can take some of course)
A bolt is used to clamp and should not see much shear when used right. The clamping force will mate the surfaces of the spacer together with enough strength that they will not shift. And even when the bolts would only be finger tight there are multiple (7) shear layers and multiple (6) bolts. I bet that the freewheel mechanism will give up long before the bolts do...

http://www.engineersedge.com/material_s ... _calcs.htm

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Re: LightningRods mid drive kit

Post by LightningRods » Oct 07, 2017 1:19 pm

I’m glad that there’s so much interest in these parts. I do appreciate all of the input.
Zlagger is going to take a shot at machining the spacers in two thick blocks. I’m hoping for 6061 aluminum that I’ll get hard anodized.
Between the splines on the stainless steel sprocket engaging the freehub and the friction between the spacers and sprocket I don’t think the class 10.9 hardware is going to see much shear force. The plan is to have the back spacer countersunk and the front spacer tapped. If I could find an off the shelf bolt that was unthreaded until exactly the point where I want threads I would use it.
I may also make a thin spacer version that will allow multiple sprockets with 8 speed spacing. Users could have 3 to 5 sprockets, wide ratio, centered for less cross-chaining. The main limitation here is how large a ratio jump we can have from one sprocket to the next and still have decent shift quality. I’d like to be able to use an 8 speed indexed shifter.
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Re: LightningRods mid drive kit

Post by izeman » Oct 07, 2017 1:53 pm

SlowCo wrote:
izeman wrote:john it's not about: will it break or not, it's about doing it right or not.
screws are just not made for what they are used here. they are there to clamp parts together primarily and not for shearing forces (though they can take some of course)
A bolt is used to clamp and should not see much shear when used right. The clamping force will mate the surfaces of the spacer together with enough strength that they will not shift. And even when the bolts would only be finger tight there are multiple (7) shear layers and multiple (6) bolts. I bet that the freewheel mechanism will give up long before the bolts do...

http://www.engineersedge.com/material_s ... _calcs.htm
ok. this will be my last reply to not become even more offtopic. lightning rods looks for the best design and likes to tinker to get 100% perfect results. that's why i posted the first time.
and now back to your post: if you look at the picture in your link you'll notice that it shows a BOLT. just because a screw is not a bolt. and if you try to search a bit deeper (google for "screw shear force" and don't be surprised if you get results about "bolts" only),you'll notice that it's just bad practice to use a screw that way. but maybe they told me wrong at university and they were all wrong.
your arguments may be all correct, and it will not break, and as i said: it probably won't matter. but you still use bolts and not screws for the job if you want to do it right. period.

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Re: LightningRods mid drive kit

Post by LightningRods » Oct 07, 2017 2:17 pm

Spinningmagnets has offered to help me source exactly the optimal bolt. I can’t argue against using the best possible components. Thanks for your time.
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Re: LightningRods mid drive kit

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Re: LightningRods mid drive kit

Post by Dogboy1200 » Oct 08, 2017 6:20 pm

SlowCo wrote:
izeman wrote:john it's not about: will it break or not, it's about doing it right or not.
screws are just not made for what they are used here. they are there to clamp parts together primarily and not for shearing forces (though they can take some of course)
A bolt is used to clamp and should not see much shear when used right. The clamping force will mate the surfaces of the spacer together with enough strength that they will not shift. And even when the bolts would only be finger tight there are multiple (7) shear layers and multiple (6) bolts. I bet that the freewheel mechanism will give up long before the bolts do...

http://www.engineersedge.com/material_s ... _calcs.htm
I agree entirely. This is why every motorcycle rear sprocket I have ever dealt with (and that’s a lot of bikes) has the rear sprocket bolted on. All have a hub in the center that supports the sprocket so only the shear force due to tourque is the only force that acts on the clamping force of the fasteners. The splined shaft on this set up replaces center hub on a motorcycle set up. This is how it’s commonly done on well engineered stuff.
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Re: LightningRods mid drive kit

Post by LightningRods » Oct 08, 2017 7:26 pm

I feel that the most significant issue with having a fully threaded bolt is that the threads act as stress risers. It's much easier for a crack to start in a sharp valley like a thread than on a smooth shaft. If there is shear stress on the bolts it will be greatest at the sprocket. I hope to find a bolt that is unthreaded to that depth. It might not ever be an issue with the splines and the crush between the sprocket and spacers. There's no harm in being doubly sure.

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Re: LightningRods mid drive kit

Post by ScooterMan101 » Oct 09, 2017 1:03 am

Mike,

Try to find Aircraft , AN bolts that are the right size.

AN bolts can be found at your local Airplane Mechanic Shop/Hanger.

Once you know what to get you could get them online these days .

I have experience with them in an Emergency Landing on soft sand,( Hanglider Trike ) I nailed the Landing perfectly in a very small area , but the Soft Sand put an abrupt stop to my landing roll resulting in some bent tubing at the front landing gear and front strut , they did not sheer off, instead they bent and by allot , If I had not seen it for myself I would not have believed how much they bend without braking .

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Re: LightningRods mid drive kit

Post by zlagger » Oct 09, 2017 10:10 am

WOW! Such a passionate discussion about bolts and screws. Had me laughing pretty good, honestly.

As someone who has worked almost 15 yrs in the machining trade, I can tell you that most design are iteration of the initial idea. If a weekness presents itself, the design is rev’d up to the next iteration. The work I have seen Mike do on this thread has presented well above average design skills and a relentless desire to better his product.

So how about we see how this turns out, and we can all get back to drooling over his great work!

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Re: LightningRods mid drive kit

Post by LightningRods » Oct 09, 2017 10:21 am

I love quality hardware so I get where people are coming from. This discussion has been enjoyable. I haven't felt like anyone has been going for my throat.

I'm excited to see what you can do with machining the spacers, Rich. This should be a very cool part when it's finished.
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Re: LightningRods mid drive kit

Post by Ecyclist » Oct 09, 2017 5:13 pm

Mike, you can totally eliminate the problem by using 3 dowel pins and 3 bolts. Or you can go 4 and 4. Simple, cheap, and effective.

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Re: LightningRods mid drive kit

Post by LightningRods » Oct 09, 2017 5:30 pm

Thanks ecyclist.
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Re: LightningRods mid drive kit

Post by LightningRods » Oct 19, 2017 4:29 pm

We've made solid progress on the single speed free hub adapter. Zlagger just happens to have several large 5 axis CNC machines laying around. Just the thing for machining complex shapes like freehub splines.

The first three images are CAD renderings. The red and blue anodizing is just to show the front and back of the two part spacer.

Image

Image

Image

This is the first physical prototype of the rear spacer, hot off of the 5 axis mill.

Image

I did decide to go with three 1/4" locating pins and three stainless steel bolts. I also decided on captive Nylock nuts instead of threaded holes. That eliminates the heartbreak of stripping tapped threads in an aluminum spacer.

If anyone is interested in one of these assemblies please let me know. Zlagger is a good guy but he can't make these for free.
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Re: LightningRods mid drive kit

Post by KarateDoc » Oct 19, 2017 4:36 pm

This looks pretty cool and I may be interested in one. I have yet to get my single stage kit going. Near completion of the fabrication, just need to mount the battery and program it. Since I don't plan on pedaling much, a single speed may be worth pursuing. What gear(s) would you be making?
New to Ebikes, building a Santa Cruz Bullit with a single stage small block Lightning Rods mid drive, EM3EV 50v7p30Q battery, Cycle Analyst V3, Lyen 12 Fet Controller.

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Re: LightningRods mid drive kit

Post by LightningRods » Oct 19, 2017 6:28 pm

I'll make whatever tooth count there is a demand for. The sprocket I'm working with now is a 48t. Combined with the single stage drive overall motor reduction is 13.7:1. This would be a good ratio for 72v and above. You might want a higher gear for 13-14s.
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screw

Post by John Bozi » Oct 20, 2017 5:52 am

No idea this was still going sorry.

guys the screws and bolts are not worth mentioning. No way they would have ever been a problem. If they were those weak ass alu things (ring nuts?) bicycles use YES! The pic I posted had a broken head from my own force of trying to get the dam thing in.

On top of that, even though I ran a pack of stainless,before that I was running alu bits bolted together and with alu "sprocket arms" too with only slight spline wear no other problems.

This is under tremendous amount of torque.

Priorities, if I did this again would be the swing arm meeting the pivot points and as mentioned the freehub twisting. The star mechanism the way the teeth engage on mine only had micoscopic wear. I still cant really explain my hub body taking force to one side a bit too much? and finally got pulled away... probably just the constant swing arm crab...

my tip is get the right frame or get lucky.

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Re: LightningRods mid drive kit

Post by LightningRods » Oct 23, 2017 9:39 pm

The prototype rear half of the single speed sprocket carrier arrived in the mail today. We wanted to check the fit on the spline before CNCing the other half. The spline fits perfectly. I took some careful measurements off of the free hub and tightened the tolerances up over the cassette that was on the hub. Time to make the front half!

Image

The locating pins are an interference -.001" press fit on this half of the carrier and a snug +.001" slip fit on the front half.

Image

Image
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Re: LightningRods mid drive kit

Post by LightningRods » Oct 24, 2017 12:19 am

The stainless steel sprocket fitted to the carrier.

Image

Image
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Re: LightningRods mid drive kit

Post by izeman » Oct 24, 2017 2:12 am

excellent engineering. part pr0n :)

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Re: LightningRods mid drive kit

Post by howlndog » Oct 24, 2017 11:11 am

I have been running one of the early kits for a number of years. So much fun! Unfortunately, the jackshaft axle of the primary drive has broken. I see the Lightning Rods website sells new jackshafts (http://lightning-rods10.mybigcommerce.c ... haft-axle/), but will they fit my particular set-up? They are visually a bit different as the new ones have c-clips on both ends. My original. does not.

My second question is that is there anything else I should be doing (upgrading) while I've got mine torn apart?

Derek

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Re: LightningRods mid drive kit

Post by LightningRods » Oct 24, 2017 12:01 pm

Yep, those early 12mm jackshaft axles had a tendency to break like this. There were several factors that caused it. First, the relatively small diameter of the axle. Second, the metal that they were machined from. Third and most to blame, the deep tapped hole in the center. This tapped hole turned the small diameter rod into a tube, which was even weaker. Add to that the machined keyway and a retaining clip groove between the sprocket and the bearing, and it's pretty well compromised.

The new axles are 4140 hardened chrome moly steel, they're 15mm in diameter, and they're solid with no tapped center hole or rear clip groove. I have not had one break yet. The length of the new axle should be the length of your original plus the outer retaining clip groove and last bit of axle. It's about +.160" per side.

If you want to upgrade to the new axles you'll also need new 15mm ID bearings [same OD to fit your original housing], a new alloy freewheel hub with 15mm bore and a new 219 driver sprocket with 15mm bore. The axles are normally $50 but I'll make a replacement for $30 for customers with the old 12mm axles. The 15mm ID bearings are $10 each. The hub is $20, the sprocket is also $20.

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Re: LightningRods mid drive kit

Post by Remus » Oct 24, 2017 10:52 pm

Hi folks,

I'm close to getting my 1500w rebuilt up and running.

I recently mounted the motor and chainring and noticed a fairly aweful chain line (Please review picture)
Does anyone have any idea's how I can improve my chain line ?
20171025_084315_resized.jpg
20171025_084315_resized.jpg (70.17 KiB) Viewed 530 times

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Re: LightningRods mid drive kit

Post by howlndog » Oct 25, 2017 3:17 pm

LightningRods wrote:Yep, those early 12mm jackshaft axles had a tendency to break like this....
Excellent, thank you. How do we make this happen?

Derek

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Re: LightningRods mid drive kit

Post by LightningRods » Oct 25, 2017 3:35 pm

PM sent Derek.
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