Pusher-Trailer: A Bicycle-Frame Solution

[rebelpilot]

It's been ten years or more since I used the trail-a-bike, but if memory serves me correctly once the kids hit about 80 pounds the tail would wag the dog, and the rear tire slid sideways. Certain terrain could cause an oscillation at even moderate speeds. I currently take up to 100 pounds in my Wike trailer, and have only a minimum effect. I can feel it tug sideways, but it doesn't ever cause a loss of traction. I have gone very fast with this trailer. I believe the lower hitch point is partially responsible, but also the fact the Wike trailer has two wheels helps.

[Kingfish]

Update:
The Plan is moving forward. I’ve started a spreadsheet to track the deltas. Key to everything is finding a machinist willing to craft a few parts: If I had a garage I could do it on my own with a welder and hacksaw; gosh if I only had access to a lathe. Anyway that needs sorting.

Slightly OT:
The good news is that the Taxman cometh and he taketh much less than anticipated leaving me free to open the purse strings for this adventure. I am excited! Spent last week refining the route and calculating the distances on http://www.Bikely.com. My longest and most difficult days are coincidentally the very first and the very last. Using the parameters and achievements of last summer, I am betting that I can go 35% farther and 35% faster by using two driving wheels over the one.

AMENDMENT:
Just to be clear: I will be carrying more batteries so as to go the distance

Back to Trailering:
Rebel, I am with you that the lower attachment will make a difference; it is how the BOB IBEX trailer mates. One thing I did note is that the pivot point on the IBEX Frame is at a slight forward angle, thus I presume that has to do with handling through a curve, as well as dampen wag/oscillation on the straight and narrow. I may need to consider how to adjust this angle through the connection between the rear axle and the steerer.

Pictures:
There are two frames that I have centered upon. One is cheaper, though I do not much care for the color, and the one I like is quite a bit more. I suppose it doesn’t matter; the majority of the “trailer” frame shall be covered with bags. Oh wait, crap the ugly color frame has been discontinued; well that’s me done – I’ll need to shell out another $130 to get white. The image below is the 26” frame from DMR. And the one below that is the Battleship Gray colored one that has been discontinued.


(Not keen on Red.)


Looks like DMR quit making 24” frames after 2009; no mention of them.

I’ve decided upon the 24” frame with the 135mm dropouts because I will be able to stay with the 24” Hookworms and matching Kris Holm Unicycle rims that I had previously purchased. To the best of my knowledge there isn’t a true BMX frame capable of accepting a 2.5” wide tire on the planet. The DMR Transition Frame is… well the name says it all: A transition between BMX, Jumper, and MtB. The frame can accept both Vee- and Disc brakes.

Unfortunately I do not have a spare 9C 2806 RH, so I’ll need to fetch one of those.

Lining my ducks into a row, KF

[Lemlux]

KF:

Recently I bought this 17.5" 1993 cromoly Giant atx 770 frame for $20 off of Craigslist planning to use it as pusher.

giant atx 770 frame

giant_frame.jpg (9.32 KiB) Viewed 1410 times

I thought I'd buy a 28" BOB trailer yoke (I have a BOB Yak with stock 26" yoke) to connect the Giant frame, but haven't yet determined a mechanically appropriate way to connect backward leaning 770 headtube with forward leaning BOB yoke pivot.

I'm leaning toward using a 24" wheel on this 26" frame for torque reasons. I suspect that a 20" wheel might lead to ground clearance issues at the bottom bracket, but I'm open to that possibility. I'm still musing about where to mount the battery but think I may center it on the underside of the downtube if it fits. For stability reasons I don't think I'd put any additional weight (except controller) on this bike frame trailer.

Looking forward to go to school with your project!

If all else fails I've toyed with the idea of cutting off the front triangle and welding the rear triangle to the back of my Bob YAK.

[gogo]

Back to Trailering:
Rebel, I am with you that the lower attachment will make a difference; it is how the BOB IBEX trailer mates. One thing I did note is that the pivot point on the IBEX Frame is at a slight forward angle, thus I presume that has to do with handling through a curve, as well as dampen wag/oscillation on the straight and narrow. I may need to consider how to adjust this angle through the connection between the rear axle and the steerer.

Yes, the angle of the pivot determines whether the trailer will lean with or away from you. To easily demonstrate the effect, simulate what will happen when the trailer is at 90 degrees to the bike. The pivot junction will rise and lean with you if slanted forward and if slanted backward will fall and lean away from you.

Check out the pics on my thread:
Subject: My project at mid-completion: It works!

That was starting out with a mini-chopper frame that had a 45 degree angle to start with and so when I turned it upside down it was just right. I'd think you'd have to do some modification to get a regular frame to work.

[Kingfish]

Hi Gogo

It’s interesting that you thought of inverting the frame; that had crossed my mind as well. Here’s my brief study:

• On the left is the frame rotated 16°. The ground clearance is less, but acceptable. Unless I’m riding over boulders and curbs – what does it matter?
• On the right is the inversion. My only concern in this orientation is the strength of the framework to take abuse. Realistically the frame is in tension, compression, and torsion when pedaling and landing. The ability of the frame to withstand shock is huge. I am convinced it can handle a 150 lb static load as a road trailer without issues. Off road, well – it’s going to see some horrible off-road this summer for a brief section, but then I won’t be taking that at 30 mph… no – more like 5 mph.

When inverted the angle will lean backward as oppose to forward. I do not think that will make a difference, so long as it leans. The angle at which it leans will determine how high the head/crown rises relative to the turning radius and angle of attack.

Reference:


BOB YAK


BOB IBEX

From these images the angle appears to be slight. I’ll try to do a bit of deterministic discovery later this afternoon on the BOB IBEX in my possession.

Inverted, however so slight - KF

[gogo]

Hi Gogo
When inverted the angle will lean backward as oppose to forward. I do not think that will make a difference, so long as it leans.

Just to be clear, forwards/backwards changes whether it leans with you into the turn, or away from your direction of turn. If your angle is shallow enough it might not matter?

Another option is to get a rear suspension bike and put an extra long shock absorber on it. By choosing the correct length of shock you can get the head tube angle dialed in exactly where you want it while preserving ground clearance and proper orientation of the rear fork ends.

[Kingfish]

Hmmm. Well I measured the BOB IBEX and the angle is precisely 80° relative to the trailer bottom. However we can see in the pictures that the angle of the bottom to the ground is relative to the height of the rear axle; a tall tire could neutralize the effect, whereas a smaller tire would increase it.

With reference to the previous DMR pair of images overlaid in CAD, if I took the inverted frame (on the right) and lowered it till we had an identical angle with the BOB then the DMR head would be well into the dirt; completely unacceptable. The frame on the left when rotated to 90° relative as shown has a bottom-bracket clearance of roughly ½ of the radius. If it was rotated another 10° that would cut it to 1/3 the radius. These are 24” diameter wheels, so quick math says this will be 6” and 4” respectively. I am not terribly whelmed by the thought of having only 4” of clearance. BTW – the frame on the left has a backward 7° angle.

Gogo, I am not sure that I follow you on the front shock theory; wouldn’t that promote a rear-leaning angle?

In another direction, who do we know that builds bike frames? Maybe it is cheaper to fab what we want?
Undaunted, KF

[gogo]

Gogo, I am not sure that I follow you on the front shock theory; wouldn’t that promote a rear-leaning angle?

Its the rear shock that would need to be longer.

[Kingfish]

Ahh, gotcha. Need to model it to be sure - but I see the direction.

I couldn't resist admiring this article on Wikipedia: Trailer Bike. That's one happy kid with a contagious smile in the first pic

Although I wish to redirect your attention to the last one at full height that is in my mind worthy of a quick study:



In this particular case, the mounting of the two frames appears to be perpendicular to the axis. That is however not the point I wish to consider: Imagine the front wheel and steerer tilting backward about 10° or so. You lean left, you turn left, the bike wants to go left... If the front section connected to the rear in the same manner, with the front frame acting like the front wheel relative to the frame, would not the rear frame follow accordingly?

Perhaps you are correct, that with small angles - it might not make any large difference. There's really only one way to know for certain
Tempting... KF

[Lemlux]

Another stability factor to consider:

Others have posted that pusher handling tends to be less squirrelly the greater the distance between the bike's rear axle and the trailer to trailer hitch pivot joint. This was one of my motivations in chosing a 28" wheel BOB yoke (BOB calls it a "fork") to attach to the pusher frame rather than using the 26" wheel yoke.

[Kingfish]

Hi Lemlux; that would make sense. Using the bike frame puts the wheel behind the axle at least 14” (minimum clearance) + 30” (minimum length of frame from head to rear axle).

Brief status:

• The project is officially moving forward with the purchase this week of quantity two of the 12 x 4110 MOSFET Extreme Modder Controller LYEN Edition. Also I ordered up another set of Rear LED Taillights and Turn Signals for the trailer; duplicates of what I have for the ebike.
• I am close to placing my order with ChainReaction in the UK for the frame and associated parts; it’s free shipping if the amount is over $250, so I want to get as much in from them as possible. The sticking point is the Mavic EX271 rim:
  
  
  • I mistakenly bought the EX729 Disc rim and mounted a 9C 2806 FH to it, not realizing I have rim brakes. The order must have been placed on the day I skipped breakfast and subsequently spaced out. Thread: Rim Brake on a Disc Rim.
  • This has led to exploring if one can just swap out the cover and convert it to disc, although I fear it might be a lost cause. Otherwise the options are to either buy a disc hub motor or a Vee-Brake capable rim and then swap that out. Regardless it is a money pit: Whatever the outcome, I’ll still need to fetch a 9C 2806 RH; the only rear hub motor that I have was taken apart to stuff 10-AWG wires through it. Thread: DIY 10awg phase leads through axle in 9C hubmotor.
    Sadly I honed the hole out to make enough room to put the wires through and now I don’t trust the axle to handle the weight and shock. In the end, this mod was unnecessary because I am not pushing enough current into the motor to be worth it. Anyways, I’ll need a new RH. Already have the rim for it: Kris Holm 24” Mountain. That will be mated to a 24” Maxxis Hookworm (already stocked). So the wheel business is almost sorted.
• The electrical system will be modified shortly. I have all the parts I need now – sans the two controllers which should arrive this week. Partial Thread: Advancing the state of Ebike Electrical Wiring. The difference here is that I will need to decide where the 2nd controller will live: On the trailer or on the ebike. If it’s on the trailer then I’ll need to pass all the signal wires and power over with connectors. Or if I leave the controller on the ebike, then it’s just 3-phase and Halls (as well as the brake/signals). The latter option pretty well keeps it simple.
• Speculating: The VKP60M312 DC-DC converter puts out 60W total. I figure the 3.3V circuit driving the LED blinkies and headlights won’t take more than 2A, but let’s say it takes up to 3A/10W. That leaves 50W to drive the 12V circuits, LED brakes and signals. I am guessing that the 12V regulator on the controller does not push beyond the maximum limit at 1.5A each (times two), but if it did, that’s 3A @ 12V = 36W.
  The part that I don’t know is the current draw of the signals and brakes, though it can be measured. The question I have is what formula should I use to determine the proper capacitor size to assuage the voltage drop during signaling/braking?

The saga continues. KF

[Kingfish]

Found another frame style having several manufacturers offering variations upon the same theme.


Product Link. This can be had for $300-390 range depending on the postage/insurance deal. Near as I can tell these are all made in China.
EDIT: Cropped a copy of the image from original source and colocated on my server for faster response.

What's interesting is that the "trials" bike frames are available in two models: no-seat & the "Street" (with seat) version. The Street version has a longer seat tube. Either way, in most cases the BB is up higher; having greater ground clearance. The price of these frames run close to parallel to what one might expect to performance bikes. The frame weights are about 3.5 lbs being made of Aluminum 6061. Not sure how that would pan out for overall strength, but I've seen video of what people are doing with them and I believe the frame can handle a 100 lb load as a trailer bike.

Caveats: One needs to pay close attention to the rear drop-outs; they should be parallel for better strength. Most accept 135mm wide, and also have integrated heads 110mm long; a very compelling geometry.

For a good list of what's out there, check out TartyBikes in the UK. There's also PinkBike and TopGears.

The question begs: What's the widest acceptable tire width? And should I go with the 24" or the 26" for a slightly longer wheelbase?
ADDENDUM 1: 4/24 - Just got an answer back on the frames above; they can accept a 2.5" wide tire.
ADDENDUM 2: Confirmed by rep that the Head Tube accepts 1-1/8th size steerer.

It's captured my fancy, KF

[Kingfish]

Oh man! Yeah, I think these frames can handle a little trailer action. Check this out; well produced film of Danny MacAskill...



Wow! KF

[docnjoj]

Hey KF! He does the most incredible stuff I have ever seen on a bike. Maybe like the old Kevin Costner film we should nickname him "Dances with bikes"!
otherDoc

[Kingfish]

I’ve narrowed my new-&-revised search for a frame down to these two beauties:

Class: Trails Frame (seatless)

• BECAUSE-2011 SIMPLE 26 Frame @ $300 USD + $40 shipping; link to seller
• Neon Wing 26" 2010 frame @ $390 USD + $45 shipping; link to seller

Both frames are within 5% of each other in terms of weight, length, and head rotation. Although I think that the Neon Wing is a better-built and stronger frame. The question though, is it worth $95 more?

Here’s the layout of the Because Simple 24” frame in CAD:


Note: Frame is rotated 15° CW in this view (the spec says the head is actually rotated 72° rather than 75°)

This class has the highest ground clearance when rotated. At 15° the BB still had about 8” of clearance with a 24” tire; that’s livable. The 26” frame will have lightly better clearance over the 24", and with the Neon Wing slightly edging out the Because Simple. The next step up in BB clearance becomes really pricy.

Kicking the tires, KF

[Kingfish]

Status:
Been quiet on this front although I have been very busy moving forward with acquisition of parts and supplies, advancing on design work, and generally setting myself up for a nice long 2000 mile trek. Items that have been sorted to date are:

• Controller 12-FET LYEN, QTY-2
• Hub Motor 9C 2806 FH
• Hub Motor 9C 2806 RH
• Mechanical Calipers; I may or not use these, but I have them nonetheless.
• CA, Direct Plug-in; already had a spare, so total of 2.
• Rims: Mavic EX 729 Disc, Qty-2
• Rim: Kris Holm 24” MtB (rear pusher)
• Hookworms, both 26” and 24” with tubes.
• Crown & Steerer, Marzocchi 888 Flat: OK, I was going to snag a used one off of PinkBike but the experience has left me with a lot of wait and doubt. At the same time I am staring at my unused Marzocchi 888 DH fork thinking that I can just take the parts off of it for free. They can always be put back on or replaced later. So that’s about $136 saved. Also might as well reuse the Frame Protectors as well.
• Connector, 6-way; on its’ way from Amazon.
• Signal Lights
• Rear taillight
• Controller mods: R12 and caps upgrade on its’ way from Digikey.
• Routes: All laid out on http://www.Bikely.com; it’s about 2000 miles round trip. BTW – I shall be passing through San Francisco and Portland for overnight on the return leg back up to Seattle/Redmond. The first and the last days will be the hardest and longest.

Left to do:

• 26" Frame, MtB DMR Transition; leaning pretty hard on the 26” frame over the 24” due to the width of the Hookworm. Not yet ordered. I am still toying with having a frame builder make a custom from frame parts. Check out these guys: http://www.cycle-frames.com/
• Headset, FSA Orbit BMX; not yet ordered.
• Trailer Hitch: This is a custom designed part that I am working on that will integrate the double-crown steerer to my rear axle. The design is nearly perfected.
• Rear Rack: I am hoping to use an off-the-shelf design; won’t know until I get the frame sorted.
• Battery bags: The trailer-bike is designed to carry Qty-48 Zippy FlightMax 5S1P 5000mAh 15/2C. That’s 24 batts per side, likely in a 3x3x4 (tall) configuration in saddlebags over the tire, equaling about 75 lbs.
• Faring: tbd.
• Batteries: Not yet ordered. Though I anticipate it will be 36 + 6 (to replace 6 bloated batts). This will bring my total up to 72 batteries.
• There’s one other mod that I am working on; the design is complete and I am negotiating with the machinist on price. The mod will allow me to mount a Campagnolo 53T triple chainring & derailleur onto my DH bike frame, allowing for a 53-11 ratio which I hope will allow sustained pedaling in excess of 35 mph with comfort. This mod is key to my success this year as it will allow me to increase my average speed by up to 10 mph over last year.
• Steering Dampener/Stabilizer: tbd
• Charger upgrade: tbd. Essentially I wish to raise the output from 700W to about 1200W, if possible. The present system is bulky, and I am not too keen on adding more to it for greater output.
• Wiring: got plenty, it just needs doing

So the short story is “Yes” I am still moving forward with this project, and there is a lot left to do. If the employment gods are kindred to my plight then I should be able to take July off and complete the journey. Too bad there’s no room for my guitar. Prolly just as well; I play horribly – though well enough to amuse myself. <sigh>

Sawing away at the ball & chain, KF

[Lemlux]

Very eager to read and see more about your custom designed trailer hitch. I have focused on the BOB 28" hitch only because I'm not aware of anything better. I'm also planning on going the cheap route with the $20 cromoly Giant MTB frame I showed earlier. It would appear to require sticking the steerer tube up in the air and welding or bolting something below the bottom of the steerer tube and tilted backward to get appropriate ground clearance and the 80 degree angle.

Per your comments on another thread, I/m particularly curious about your TBD steering damper / stabilizer presumably somehow connected through the steerer tube.

[Kingfish]

Hello Lemlux

I placed the order yesterday for this: Streamline Steering Stabilizer 7 Way Rebuildable Black



Search eBay; the seller is “atv_zone”. My total cost was $124.20 USD. It closely resembles the steering dampener that I had on my Honda Odyssey. Ultimately the desire for the 7-way adjustments and be rebuildable won out over the other device. Not sure if the clamps will be of use though. BTW - the seller was pdq on getting this order out first thing this morning and I already have a UPS tracking number

Frame: Correction...
The frame will be a 26” Neon Wing Trials weighing in at 3.5 lbs. I’m nearly convinced this would be easier than trying to get someone to weld up a custom bike frame. If I did the welding route then the tubes would be either Aluminum 6061 or Steel Alloy 4130 – all thin wall stuff. However every frame builder out there looks like their minimum is $1200; I’m better off modifying from off-the-shelf. So this will likely get ordered this week.



That's pretty flat! Any more and the price escalates rapidly

Hitch:
The present design has the hitch made from four elementary parts with some extra pieces; below is an analogy of one side. First, there is a design constraint with the rear axle on the right side where the derailleur is located; chiefly the location of the hanger restricts freedom of movement. Therefore a study was made to consider moving the trailer mounting point farther back behind the axle.

• Custom Rear Axle: 12mm through the Hope Pro II MtB hub, transitions to 10mm flats through the frame, but is extra-long to accommodate the adapter described below. In this manner the axle is self-locking in relation to the frame for when I secure the axle nuts.
• Axle Adapter : Moves the pivot connection behind the rear axle so the hitch assembly has better freedom of movement. The adapter will mate to the rear axle and use a shoulder screw as a pivot pin for the bracket.
• Bracket: I’m still sorting this out; might make it from plate, might be a weldment. Plate is simpler, weldment lighter and stronger. The bracket mates to the adapter pin by way of a bronze bushing, and secured with washer and nut. That’s one half of the mounting problem done; bike to hitch. Now we resolve the hitch to trailer-bike connection.
• Fork Clamp (2X/side): Basic C-Clamp designed to fit a 38mm steel tube and affix it to the other end of the bracket. The tube emulates the upper fork and is mated to the crown & steerer which follows using typical hardware.
• The Frame protectors will go on the 38mm steel tubes.
• A custom mounting is likely required to affix the steering dampener/stabilizer between the bike frame and the 38mm steel tube. We only need one, and I’ll put it on the right side.

That was as of last night. This morning I had an epiphany on how to simplify the design yet again, so it’s back to the drawing board. Actually I really enjoy engineering studies because ultimately the rewards are in the pocket

With crayons, KF

[Kingfish]

Frame Correction Part Duex:
Ack! The last couple of days have been fraught with naught! The seller of the 26” Neon Wing Trials was slow to get back and relate that the Disc option is no more; he's out and not getting anymore. Unfortunately there are few worldwide suppliers of this – apparently rare configuration – that sourcing a replacement was next to impossible

On top of that I have learned that BECAUSE, NEON, and BORN are all of the same manufacture, or at least in league with each other to covet/control the market (they share the exact same cookie-cutter website layout). With my options quickly running out, my choice was to forgo the Disc option altogether, perhaps entertaining the “Brake Therapy Disc Brake Conversion Kit”, or to move away from Trails Stock frames to hybrid 24” frames with Disc. Ultimately that’s what I did, reverting back to the Because Simple Trials White frame as previously suggested. With no domestic supplier, I went to http://www.TartyBikes.com and paid $442 after shipping and insurance.



Brake Therapy Disc Brake Conversion Kit: These run about $136. There was no guarantee it would fit the frame, rotor, brake, & hub, therefore I elected not to entertain the risk.




24" Because Simple Trials: I snagged the white frame from TartyBikes in the UK.

Custom Widget:
The Revision-D passed muster with my machinist and he has provided a favorable quote this AM; we are proceeding forward with a prototype and I hope to have it in hand for testing shortly. The widget will allow me to mount a Campagnolo 53T triple chainring & matching derailleur onto my DH MtB frame.



The parts necessary for the potentially-fastest pedal ebike: 53T Chainring & custom Phil Wood BB

Hitch:
Now that I know how the frame will be I can finally sort out the hitch details and get that off to the machinist as well.

Honorable mentions:
People running these sites were helpful in educating me on what I needed to know about the trials frames.

• MidWestBikeTrials
• TopGears
• WebCyclery

Moving forward, one day at a time, KF

[Kingfish]

Status

A great week for parts.

The 24" Because Simple Trials that was ordered on Tuesday arrived at 10:30AM on the nose Thursday from the U.K.; evidently TartyBikes shipped it to me expedited ~ no complaints, just big wide smiles! Inside the box was a nice large black T-Shirt from TartyBikes and a lower chain stay protector; very nice schwag! The frame is in great condition, feather-light, and built strong. My only concern are the drop-outs which look a bit thin on material. From the specs, my CAD drawing required very little modification after having the frame in hand. Overall, it is a very impressive bit of construction and I am quite pleased.

Steering Dampener: Arrived in good shape & reviewed.

90 Degree Valve Step Extension: Basic yet essential convenience for my ebike; reviewed.

Headset: Decided on only the best and ordered the Cane Creek 110 in Black from eBay for $91.49 total with shipping.

Charger Upgrade: I need an upgrade to keep pace with the time it will take to charge the large pack. The later postings on the How-To: Meanwell 63-84V CV/CC Charger thread discuss my findings, though suppose it couldn’t hurt to announce here that the unit selected and ordered is the HRP-600-24 and -48, one each to create a 63V 600W charging array. Cost was about $360; should arrive around Tuesday-Wednesday. $pendy, yesssss ~ I know. But then it is a crucial piece of equipment just as important as the trailer frame, and we can’t afford failure. The new assembly is roughly twice as powerful with less volume for the same weight.

Hubs: E-BikeKit says the front hubs arrived yesterday and mine will ship out Monday. These are the 9C 2806 Disc models, Front & Rear. My present FH is not disc; rim brakes are so noisy and I look forward to this upgrade. The new tire will be the 26”x2.5” Maxxis Hookworm. The rear tire will use the Kris Holm 24” MtB rim mated to a 24”x2.5” Maxxis Hookworm. I was sold on this rim after watching the guy perform some incredible feats!



That’s all I knows from this front. More to come.
Dutifully, KF

[Kingfish]

Status
It’s been a week since my last post; here is what has changed.

• Headset: Delivery delayed till Monday. I kinda need that to finalize my design this weekend; bummer.
• Charger Upgrade: Done! Review: Meanwell HRP-600 Series & How-To: Meanwell 63-84V CV/CC Charger. This is a hug win as this upgrade literally cuts my charging cycle in half. I’m still not out the door though: There’s a tiny detail with cutoff that needs to be addressed to prevent overcharging.
• Hubs: In transit and expected on Tuesday.
• Custom Widget: Received from Machinist on Wednesday; looks sharp and hope to have it mounted this weekend.
• Throttle: Replaced failed throttle with a similar HE throttle for now. I may or not upgrade to the Magura; depends on how the Lyen Controllers adapt when the time comes.

Custom Hitch:
I went round and round on this knowing that the machinist is the most expensive route and trying to create thrifty alternatives. Yet each time I have been frustrated by the lack of- or difficulty in finding appropriately compatible hardware.

I used BeamBoy extensively although I do not trust it to report cantilever solutions correctly, being off by a factor of 10. I probably went through five complete iterations before coming back full-circle to one that just makes the most sense. Sorting out my questions, I waited a day before fetching the parts and try to get my answers direct from the machinist in one fell swoop. And I am glad I did because his welder-partner was conveniently there as well.

Turns out that um… Fate has a hand on this tiller:
My machinist built an electric-powered Chevy Luv running off 12Vx10 car batteries two years ago, and he drives this to work. It only has a 20 mile range, but this truck is absolutely clean! I’ll try to get some pics next time I’m in. The welder-associate works across the street and fabricates racing frames for motorcycles for himself and others. They’re pretty excited about my ebike and I have to think that this is a match made in heaven!

Therefore I am redesigning the hitch to be a CrMo tubular weldment assembly for simplicity, fatigue-resistance, and strength. This whole assembly will include the new axle, bracket, faux fork tubes, and fork clamps.

What’s next

• Torque Arms: Two sets; front and rear. In conceptual stage.
• Battery Bag mounting brackets: tbd
• Battery bags
• Cargo bags
• Additional batteries
• Faring
• Handlebar reorganization
• And lots of little details.

Five weeks to go.
Methodically, KF

[hekdude]

Was this the bike attachment you were thinking of


from

http://troyrank.com/category/bikes/

here is a way to attach a complete kids bike, though it is not what you are looking for.


http://clevercycles.com/products/access ... -coupling/

[Lemlux]

Hekdude:

Interesting connector, but $399?

[Kingfish]

Was this the bike attachment you were thinking of

<snip>
here is a way to attach a complete kids bike, though it is not what you are looking for.


http://clevercycles.com/products/access ... -coupling/

The design will be similar to that except that I am using a DH fork crown with the forks removed, and replaced with a “faux fork” short tube that is long enough to engage the crown & steerer. The side brackets will mount to that. By removing the forks (or rather shortening the length) the bike frame rotates forward – creating a near horizontal platform for loading up batteries and cargo. Maybe I need to post a 3D model… wait, lemme get to that shortly for a picture is worth a thousand words

~KF

[Kingfish]

Status
I was distracted by work this past week and ended up commuting to Seattle and back several times – a 45 mile loop. Nice to know my present setup can do it at nearly WOT through hilly urban terrain: 15S6P @ 27.5 W/mi; batts never dropped below 54V. New charger restored the pack in less than 2 hours.

What’s changed

• Headset & Hub Motors from E-Bikekit: UPS driver had his knickers stitched up past his ears and refused to leave my packages – two separate deliveries – with the designated terrestrial representative. Why do some Earthlings lack the capacity to follow simple instruction? Round and round we went with the driver leaving more sticky notes – and Customer Service that wasn’t. After close to a week delay – and on the second attempt to the Distribution Center I was able to fetch my packages. One appeared damaged…
  
  I dread biting the hand that feeds me but my hope is that a picture is worth a thousand words; this is not the way to ship product:
  
  
  
  Regardless, I will actively use alternate shipping if given the choice henceforth.
  
• Rear Hub: This is off to REI for mating with the Kris Holm 24” MtB rim & 24”x2.5” Maxxis Hookworm. I suspect this will take two weeks because the spokes are custom-order and my wheel-builder guy only works one day a week.
• Front Hub: I have one mounted ready to go now except it doesn’t sport the disc brake covers. What to do. I could save some dough and just swap the cores. The center ring is not painted so it might look a bit peculiar. Regardless I hope to get that sorted shortly. The front brake will need to be replaced (parts already on hand) as will the Torque Arm arrangement which brings up a good point...

Custom Parts
Knowing that machining can be expensive I have gone round and round on the designs attempting to keep things simple; match materials with stock product dimensions to maximize utility and economy. Before I can mount the front hub I need the torque arms and that is a two-week lead. Designs have to go out tomorrow. There’s a lot to do, however the layouts are completed.

I am now focused on the trailer battery box. The design initially began with each side holding 24 batteries, though now I think it should be 30. The calculus:

• Last summer on my last day with 15S12P I went 173 miles, climbing nearly 8000 feet and dropping 13000 – and averaging about 26.5W/mi overall which included a lot of pedaling. This year my most arduous day will be about 240 miles with matching ascent/descent of 12000 feet, hence the doubling of the batteries. That’s
• 36 * 2 = 72. There are 18 batteries (15S6P) mounted now in the forward triangle. 72 – 18 = 54. Split that between left and right bags 54 / 2 = 27. This is rather an uneven number:
• Stacking can be done by 2 or 3 deep. The study below shows the difference in width; 2 deep makes good sense being more streamlined. 27 / 2 = 13.5; not a convenient number, however 30 / 2 = 15, and 15 can be achieved by stacking 5 x 3. A box containing 30 LiPo bricks (Zippy FlightMax 5S1P 5000mAh 15/2C) measures roughly 17x9x4.5 and needs to withstand a static load of 38 pounds.
  
  
  
  The red dashed line in the top view indicates the relative width using the pedals. My preference is to remain slim and slippery
  
  As such, mounting this box and its’ construction has my undivided attention. I looked at several off-the-shelf solutions but the weight was in excess of 5 pounds; I think I can do better with a simple framework and bag. Anyway – that plan is developing.

For the most part things are progressing well enough. I am concerned about my time now. The batteries will have to be ordered this week. It doesn’t leave me much room for road testing.

EDIT: Batteries ordered on this day. 36 + 5 replacements. This will be enough for road testing. I can always get more if field testing suggests the need. Amazing that the HK-USA shipping price was so low; < $25. I can't imagine USPS trying to deliver 52 lbs of batteries! I wonder if HK-USA does will call?

Four weeks to go.
Antsy, KF