Eric's Project #002

[Beagle123]

A Check of the Design.

Here's the current state of things. I drew in where everything else goes to check to see what it will look like.

 

[Beagle123]

Compare to this:

 

[safe]

I hate to rain on your parade, but angle shaped frame members are good in preventing flex in only one direction. The "L" shape doesn't do well in twisting flex which is exactly the kind of flex you're going to get on a swingarm. The proper member to have used would have been box or rectangular tubing. (or even round tubing would have worked)

What possessed you to go with the "L" shape instead of the box or the rectangle?

I'm simply at a loss to understand why you're doing things this way...

For the main frame I can see using the "L" shape because it makes a good container for batteries, but on a swingarm you use box or rectangular tubing...

Also, the swingarm pivot needs to be better build than that. Aluminum will loosen up really fast with use and you're going to get all kinds of slop in that joint. I really should have taken an interest in this sooner because I might have been able to give you some tips and point you in the right direction early in the process rather than late. I suspect you're going to have problems with this frame in practice...

 

[TylerDurden]

The BeagleBike is gonna be great.

Totally unique and easily upgradable.

Go piss in your own wheaties, Safe.

 

[xyster]

The BeagleBike is gonna be great.

Totally unique and easily upgradable.

Go piss in your own wheaties, Safe.

I second that sentiment (or sediment ). Somebody should post a poll -- let direct democracy (aka 'tyranny of the majority') decide what Safe eats for breakfast tomorrow.

 

[safe]

I second that sentiment (or sediment ). Somebody should post a poll -- let direct democracy (aka 'tyranny of the majority') decide what Safe eats for breakfast tomorrow.

I really honestly don't want to appear negative just to be an annoying person, but I also know enough about frame design to know that he's made some decisions that are sure to haunt him later on. I'm not a universally negative person (I've given rave reviews to dirty d's project for example) but I have some worries about the overall safety of this design. I might be wrong... but... I really don't think I am wrong on this one. Only time and testing will show us what the result will be.

I really would prefer to be able to say: "Great Job" or something to that effect, but my conscience forces me to point out what I think will be a problem down the road.

The main frame is fine... but the swingarm is just not very good. He needs to either add some extra bracing or replace the swingarm with one that uses boxed, rectangular or round tubing. The swingarm pivot will also wear out very quickly and needs to be changed.

I hope I'm wrong... I hope my advice is totally off base...

You never know... if the thickness of the "L" members is thick enough it can resist the natural tendency to twist and be a satisfactory design. However, if it's not thick enough and it has to rely on it's natural design tendencies then the rear swing arm will flex very badly. The swingarm pivot looks to be nothing more than a bolt through a hole that was drilled. Most bikes have very elaborate bushings for the swingarm pivot, so comparing this to what's out there tends to point to a deficiency in the pivot design. He really should have started with an existing frame and cannibalized it for all it's specialty parts. Things like the swingarm bushing could have been chopped from an existing frame. (that's what I've been doing)

 

[dirty_d]

the swingarm looks like its made of pretty thick aluminum, i think that will be fine. like safe said though that pivot is definitely going to wear out fast and have too much play, its an easy fix though, you said you're using a 1/2" bolt all the way through right? just bore out the swingarm pivot holes to 5/8" and put a bronze bushing with a 1/2" ID in them, these should work(http://www.mcmaster.com/itm/find.AS...hDtlLink&fasttrack=False&searchstring=7815K28).if there is enough room you can insert it with the flange between the swingarm and frame and if there isn't you can put it on the inside of the swingarm with it held in place by a 1/2" locking collar. when they wear out simply replace them, they're cheap.

 

[Jozzer]

Its beginning to look nice. Very nice thread, its great to see so much info about people building things. Keep it up, Its very inspiring....I feel a homemade trike comin on!

I'd tend to agree that the swingarm would be much stronger in box. It does look as strong as many aluminium swingarms i've seen however (like the linear recumbents for example, though it has to be said that that is the one thing that really needed improvement on the old linears). Since you've come so far with it though, it's porobably worth trying it to see how it fares. It wouldn't be the end of the world to redesign that bit later.
Swingarm pivot doesnt look strong enough to me, but I suppose alot depends on how it will be ridden. Bushes would at least stop it from wearing itself to bits.

 

[Beagle123]

What possessed you to go with the "L" shape instead of the box or the rectangle?

I'm simply at a loss to understand why you're doing things this way...

I used L shaped members because I would have rather had a single piece of metal, than having to worry about a weld breaking on this high stress spot.

To compensate for the inferior shape, I used very thick 3/16th inch aluminum. I'm sure its impossible to bend in the vertical direction or horizontal direction. I also beleive that it would be very very hard to twist.

I can see how there can be very strong forces in the vertical direction, but I don't see how there can be a strong force in the twisting direction.

Also, I'm using 20 inch wheels, and so each arm only sticks out 11 inches. Imagine trying to twist a 3/16 piece of aliminum over a 11 inch span. When you imagine that, then add that the two arms are tied together with the back axle. So its really like having to twist 3/8 inch of aluminum.

I don't see how much of forces will be appied in the horizontal direction to the back wheel. It seems to me that even when you lean into a turn at high speeds almost all of the force is in the vertical direction.

How much force is applied in the twisting direction when you ride?

In fact, I just thought of evidence that there's no large forces in the twisting direction: Bicycle wheels that are thin (like on 10 speeds) are very fragile. If there was any large force in the horizontal direction they would be easily be knocked out of "true." Once I bumped my bike into the couch and it knocked the wheel about 1/4 inch out of true.

 

[Beagle123]

like safe said though that pivot is definitely going to wear out fast and have too much play, its an easy fix though, you said you're using a 1/2" bolt all the way through right? just bore out the swingarm pivot holes to 5/8" and put a bronze bushing with a 1/2" ID in them, .

Hi dirty, thanks. I considered bearings and bushings, but I thought it was overkill. However, I'm liking your idea. Let me explain how I was envisioning it working, then let me know what you think.

By the way, your bike looks great. I've been checking your progress daily.

Here's what I was thinking: I agree with you that drilling holes in aluminum, and running a bolt through isn't good. I beleive the friction on the metal will wear it out. So to eliminate friction, I planned to have the bolt held completely STATIONARY with lock washers on either side of the bike. The bolt should not turn at all. (in theory) So, in the picture imagine that the the bolt and the battery box are connected as one piece. There shouldn't be friction in the joint because it will be locked together.

With the swingarm, I didn't want to "just drill a hole" either. So I welded a tube connecting both sides for the bolt to run through. The idea is to dristribute the weight over the entire tube so there is no friction point. The whole inside of the tube bares the weight.

So the friction points are inside the tube and on the washers on either side.

Also, I reinforced the sides where the bolts penetrate by welding little squares of metal over that area. The sides are 3/8 inch thick. Very Very thick.

All that being said, I'm sure your bushing idea is superior. I'm not sure how I'd get perfect holes. When I drilled my last ones with a hand drill, they weren't perfect.

Here's my question: If I can tighten my bolt so it doesn't move, isn't that the same thing as using a bushing?

Also, shouldn't I have the same concern with my shocks? I'm planning on "just drilling holes" for them. The brackets are made from 3/16 aluminum. What do you guys think?

 

[Beagle123]

What I Really Need is...

Batteries!!! Help!!!

I don't know anything about batteries. Here are my thoughts:

1) I guess I want LiPo4's.

3) I'd like 25 aH or so. The slower ones that you can use at <3C appeal to me because you can charge them so many times.

3) I don't want to mess with 8 chargers. I'd like a nice plug to just plug it in.

4) I don't want to explode. (not yet)

5 The dimensions of my battery box are 11.5 inches long X 5.75 X 7.5 (I hope I left enough room.

My current plan is to call these guys:

http://falconev.com/batteries.html

I'm going to ask them what they think I should buy. I'm going to beleive every word they say, and I'm going to end the conversation with, "Sounds great. Charge it to my credit card."

Does anyone have a good battery solution? xter, I know you're out there.

 

[TylerDurden]

I think the swingarm pivot looks fine. Grease the bolt well and consider nylon washers between the swingarm and the brackets.

The shock should have a built-in bushing, so the goal is to make certain the tube and through-bolt in the bushing are totally immobile relative to your bracket. Small washers, adequate torque and thread-locker should do the trick.

 

[Dingo]

This is starting to be like that chopper show where the the dad and the son are both making a new bike... only you and safe don't seem to be conspiring against each other or sabotaging at all, which is nice to see

 

[safe]

I can see how there can be very strong forces in the vertical direction, but I don't see how there can be a strong force in the twisting direction.

There are huge forces that want to twist the entire wheel at an angle.(rotation along a line that would pass straight through the middle of the bike as looking from the back) When we talk about a "high side" crash that comes about because you enter the turn and the rear wheel loads up and the tire tread wants to twist the wheel "inward" at the bottom. If the tire looses traction it will drift out until it catches again and then the real spring effect takes place where all the weight of ther bike and rider gets wound up into the swingarm and frame. So at this point your bike is an active and loaded "spring". When the spring unloads it throws you up into the air in what is known as a "high side" crash. You virtually eliminate this type of crash with a stiff frame and swingarm.

For your case it might never bring about a crash because the flex might be so severe that it just feels like jello back there... you learn very quickly not to go very fast because you know that something is feeling really wrong. (the feedback might be so negative while riding that you tell yourself to take it easy)

One cure could be to weld an extra piece of metal across the ends of the "L" and turn it into a right triangle. Your swingarm would resist twisting because the triangular shape would not allow it.

Also, Dirty D has a great suggestion with those brass bushings. I saw some at my local hardware store and I was thinking of all kinds of ways to use them. The 1/2" steel bolt matching up with the drilled aluminum is not a good idea... but that extra bushing would make it a winner.

 

[safe]

My current plan is to call these guys:

http://falconev.com/batteries.html

I'm going to ask them what they think I should buy. I'm going to believe every word they say, and I'm going to end the conversation with, "Sounds great. Charge it to my credit card."

Guys like you will help to fund the growing EV support businesses. If you have money to spare and you want a good battery it looks like they could do it for you. Most of us on this site will buy all the source parts and build our own. It costs a little less to do it yourself, but it requires a great deal of effort to make it happen.

I've been working on my #002 Project since June and don't expect to really be completed until final debugging is complete next spring. So unless to have year long time horizons to complete your "hobby bike" it might save you a lot of time to buy things prebuilt.

 

[xyster]

Does anyone have a good battery solution? xter, I know you're out there.

I'm more trusting of the high-C powertool packs, emolis and dewalts, than the lower-C, not-well-known ebike LiFePO4 and LiMn packs. Also, a bad cell can be replaced easily; the pack can be designed into odd, frame-fitting shapes; and charged with a single RC charger with built-in or add-on balancers like how Patrick Mahoney charges his 18650s. Low voltage cut-off can be provided by the CycleAnalyst, an LVC-modified controller, or manually by watching a voltmeter -- allowing the BMS to be jettisoned or bypassed.

I'd buy as many Dewalt or Milwaukee packs as necessary, disassemble, remove the BMS's, and cut the tabs such that the tabs could be folded over wire, crimped and soldered into parallel subpacks. Add wires for the balancers between the subpacks; wire the parallel subpacks in series and in the proper shape; build an enclosure and ride off into the sunset a satisfied, proud do-it-yourself'er.

 

[Beagle123]

Thanks for your replies. One at a time:

Tyler: Nylon wasers sound great. Eliminates friction, doesn't wear the aluminum, won't squeek. Sounds like a great idea to me! I was planning on using grease on the axle. I think I might as well use bushing for the shock brackets. I don't see why not. I need to get thread lock.

Dingo: Safe and I should have our own reality show. We'll have a boxing match at the end.

Safe: I'm not sold on your "high end" crash stuff yet. I'm sure that's possible at high speeds, but at 20 mph, I can't see it happening. And I be hard pressed to think of a turn I'd be willing to take at 20 mph. I understand the force that you're talking about. I'm going to try it first, and I will report back to you if I can feel anything like that going on. If so, I think you've offered a good solution with welding it into a triangle.

I'm in total agreement with you and dirty_d that bushings are a good idea. And I sure can't see an argument against them.

Xter Thanks for the tips. I'm really going to think about your advise because I know you have some valuable experience. I have so many questions I don't know where to start.

If I buy a pre-built pack of batteries, and there's a bad cell, I'm screwed? So in other words, these packs that claim to have 2000 cycles really have no chance of making it too far because a cell is likely to screw up?

I like your idea of being able to make any size battery to fit my bike. My box is 11.5 X 5.75 X 7.5 inches. I'm not sure I can fit a good sized battery in there.

Are you suggesting that I buy batteries for hand tools like the one pictured below and take them apart?

Do you have a suggestion for where to get instructions for building a battery pack?

I know that its hard to help me because I'm "behind the curve" on batteries. But trust that I'll be researching to get up to speed.

Thanks.

 

[Beagle123]

Seat Post Cut

No big news today. I just cut the seat post tube.

My welder guy won't be available until after the holiday, so I can't do much.

 

[Beagle123]

Are these the batteries you're talking about? xter?
http://www.amazon.com/Milwaukee-48-11-2830-V28-Lithium-Ion-Battery-Pack/dp/B0009F5E5M

How many amp hours are they? How many would I need?

 

[xyster]

Are these the batteries you're talking about? xter?
http://www.amazon.com/Milwaukee-48-11-2830-V28-Lithium-Ion-Battery-Pack/dp/B0009F5E5M

How many amp hours are they? How many would I need?

Those are my favorites -- and the cells I plan on using for my next pack. Jondoh and Maytag here use them. Rated 3.0 ah, they provide 2.6 real-life AH over the typical li-ion 4.2v --> 3.6v range. What kind of voltage and range do you want?

If I buy a pre-built pack of batteries, and there's a bad cell, I'm screwed?

If you couldn't get it fixed under warranty, you'd have to replace the bad cell with something similar; or take it out of the pack, and live with less voltage and a different charger. The BMS might not like that though.

So in other words, these packs that claim to have 2000 cycles really have no chance of making it too far because a cell is likely to screw up?

I've not seen evidence of that. Usually if a cell is bad, it's bad from the get-go. A DIY pack gives you the chance to load test each cell, and exclude any that are effectively DOA, or show excessive voltage sag.

I like your idea of being able to make any size battery to fit my bike. My box is 11.5 X 5.75 X 7.5 inches. I'm not sure I can fit a good sized battery in there.

The Milwaukee and Dewalt cells are size 26650 (26mm diameter X 65mm length) -- about 1" diameter by 3" length including wires on the sides. So you could fit at least 11x5x2 = 110 cells in one direction, or 11x7x2 = 154 in the other direction if you can fit two ~3" half-packs side by side in 5.75".
110 emoli's could be a 10s11p 36 volt 28.6ah pack; 112 could be a 14s8p 48 volt 20.8ah pack, for example. It looks like you've got plenty of room for a good size pack.

Are you suggesting that I buy batteries for hand tools like the one pictured below and take them apart?

Yes -- either Milwaukee V28 powertool batteries or Dewalt 36v powertool batteries.

Do you have a suggestion for where to get instructions for building a battery pack?

Here's a step-by-step Milwaukee disassembly and pack build guide:
http://www.rcgroups.com/forums/showthread.php?t=508443
There are similar guides there for the Dewalt/A123's.
Instead of yanking off the tabs and then soldering expensive battery bars to the tops of the cells, I'm planning on leaving the tabs intact, but cutting each one in the middle to separate the cells, then using the tabs to fold over the wire, then crimping the tab to the wire, and soldering the wire to the tab. This way, I can avoid soldering on the cells, which may cause some damage. I've not seen a powertool-cell EV pack done this way, but it's basically the same method I used for the tabbed-cell li-ion pack I have now.

I know that its hard to help me because I'm "behind the curve" on batteries. But trust that I'll be researching to get up to speed.

Thanks.

No prob.

 

[safe]

Safe: I'm not sold on your "high side" crash stuff yet. I'm sure that's possible at high speeds, but at 20 mph, I can't see it happening. And I be hard pressed to think of a turn I'd be willing to take at 20 mph.

I regularly hit a top speed of 40 mph and above and I really do lean the bike over at 25 - 35 mph in turns. You seem content with a frame that will flex and you seem content to go slow, so the two things go well together.

Just never go above 20 mph and you will be fine...

And it's called a "High Side" crash...

 

[Beagle123]

I just noticed that my current bike doesn't use any kind of tubing for the swing-arm. Its just a straight piece of metal with a slight curve. It is about 1/8 in thick steel however:

 

[Beagle123]

Seat Post, Neck Welded

A couple of pics of the seat post tube welded into place, and the neck. Actually the top piece isn't welded in yet because I was concerned about the fit of the side panel, so its just tacked into place now. When you connect the head tube to the battery box with "L" shaped pieces, all the angles get weird. The "L" shaped pieces don't form right angles at the corners. The bottom sides lean inward and the top side leanss outward (when you make the top and bottom flat) So I had to bend the top pieces to about 80 degrees before installing. THere's a bit of "fudging" going on on this part.

I added a little square of metal to further secure the bottom pieces to the head tube.

 

[Beagle123]

My Thoughts on a Motor

I was going to use this 600w gear-motor made by Unite, but I think I may want to upgrade. One problem with this motor is that its 36v, and I'm now thinking of making a 56v battery pack (thanks to xter) that would fry this little thing. Also, it is the same motor as I currently use on my converted moped at 48v. I love the added performance from upgrading to 48v, but it makes the motor really scream. I can't imagine what it would sound like at 56v.

I'm now considering this motor:

Mars Brushless motor
http://www.thunderstruck-ev.com/marskit.htm

I like this motor because it can handle 2000 watts easily. I don't plan to use it that hard, but I like the idea of using high rpms and lower current (compared to the motors specs). I'd like to create a bike that humms. I don't like the motor screaming. I realized this when I was riding on a nice flat surface, and I had my bike in 4th gear, and the motor was just humming happily because it was only using about 10-15 amps. It occured to me that the motor could always humm like that. It could humm up hills, you'd just need to use a low gear, keeping the rpms up, and using a big motor that's running at 50% of its power.

One thing that I don't like is that the higher voltage (56v) means that the motor would want higher rpms. This mars motor would need to run at about 4000 rpms to maximize its efficiency. I like the idea of lower rpms.


The thought then occured to me that I don't want a huge eTek type motor on my bike. This motor look perfect at only 9lbs! Also, safe mentioned that all evs are chooing to use brushless, and brushless is about 3-6% more efficient. I can't think of the downside.

The only issue is if I have space in my frame for this 6 inch motor, and I think I do. I think the motor is narrow enough to fit inbetween two members in the back. I'm talking to Thunderstruck Motors now about it.

I'm thinking of using the Milwaukee v28 battery packs, so I'd need to run either of these setups:

28v 36ah
56v 18ah

or think about other battery options..

Then I would be using either:

24v 80 amp controller

or

48v 40 amp controller.

Do y'all know how much performance I would lose by using double the amps and half the volts? I know higher volts is better but by how much?

I'd like to settle on my battery/controller/motor combo as one big decision. I already have two motors and a controller laying around.

 

[Beagle123]

Hey Xter:

Thanks for that great advise on batteries. The article you linked to said this:

The Milwaukee Emoli packs have been working out great when used in an application that doesn't require the latest and greatest lipo cells.

I assume he's talking about discharge rate? In terms of capacity, they are comparable to all lipo cells right? What is the chemistry of these cells?

Also, if I understand correctly, the LiFePo4 cells have approx 40% less energy by volume? This would be bad for me considering I'm lacking space.

I'm still researching. I'll get back to you later.