Evolution of Skill....

[gwhy!]

Im sort of playing around with a frame making exersise my self on and off ( more off than on ).. and Im going for a pivot point just above the bottom bracket. ( Just thought you might be intrested..) here is a pic.

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[AussieJester]

Have we enough clearance between the lower shock mounting bracket and the 'upright' tube the
t'other end of the shocky attaches too, when the suspension is in full upward travel, i'm sure you have checked, just looks like it could
come close to hitting in zee pic... Nice work though.

KiM

[Lenk42602]

gwhy -

thanks for the pic!

Did you come up with enough chain clearance considering your swingarm travel? I bagged this idea cause i couldn't get enough with travel and swing arm dimensions..

AJ, the lower shock mount on the swingarm is just eyeballed for now - I figure I will fab up the arm first with the pivot and BB, get every thing square, and then get the dimensions for the lower shock mount on the swingarm, as well as te final angles for the upper shock mount/seat tube support....

len

[gwhy!]

gwhy -

thanks for the pic!

Did you come up with enough chain clearance considering your swingarm travel? I bagged this idea cause i couldn't get enough with travel and swing arm dimensions..

I hope so. its very close. once I have fitted the bearings in the pivot point and mounted the shock I will then know if for sure if it will clear, or do you mean the chain ring on the crank ? . The peddle chain/ring will not be driving the back wheel directly.

[Lenk42602]

Ahh. I was assuming an isolated pedal only drivetrain.....I meant chain "slap" based on vertical swing arm travel using a traditional pedal only drivetrain.

Hub motor/swingarm/chassis is my main concern, really just trying to get the pedal - only drive train to work fairly well around it.....

Len

[gwhy!]

Ahh. I was assuming an isolated pedal only drivetrain.....I meant chain "slap" based on vertical swing arm travel using a traditional pedal only drivetrain.

Hub motor/swingarm/chassis is my main concern, really just trying to get the pedal - only drive train to work fairly well around it.....

Len

OK, I think If I put say a 40+'ish chain ring (if It will clear the swingarm) at the cranks and run a chain to the back, the chain would run along the swing arm ( may have a little bit of chain slap ) but what I intend to do is run a piece of chain slider material where the chain may touch the swing arm. I cant say for sure, but if you dont mind waiting to make a decision when I get the bearings fitted into the pivot point I will put a chain ring on and see if it would be a problem or not. I could prob fit bearings this coming weekend if this will be of any help.

[Lenk42602]

.....if you dont mind waiting to make a decision when I get the bearings fitted into the pivot point I will put a chain ring on and see if it would be a problem or not.....

that'd be great - I am waiting for some metal to begin cutting/fitting the swing arm sections. i'm working from th axle forward, so the area between the rear tire and the pivot point will be the last area I connect...

thanks,

len

[gwhy!]

Hi Len,
I managed to put some bearings into my swingarm to see what would fit chainring wise. It would have to be a min of a 44t this will just about work on my frame ( with a 16t freewheel on the back ). The centre of the BB to the centre of the pivot height on mine frame is 70mm and the swingarm pivot centre is 30mm behind the centre of the BB, obviously if you can get the height of the swingarm pivot nearer the BB then this would give you more room to play with. hope this will be useful for you.
Cheers.

[Lenk42602]

gwhy - PICS!


what about crank arm clearance? from the photo, it doesn't appear as though your swing arm is narrow enough for the crank set to clear it?

Len

[gwhy!]

gwhy - PICS!


what about crank arm clearance? from the photo, it doesn't appear as though your swing arm is narrow enough for the crank set to clear it?

Len

I will try and get some pics for you later today. crankarm clearance is ok.

[gwhy!]

gwhy - PICS!


what about crank arm clearance? from the photo, it doesn't appear as though your swing arm is narrow enough for the crank set to clear it?

Len

I will try and get some pics for you later today. crankarm clearance is ok.

Not sure if these pics will be of use to you.

The chainring fitted in the pics is a 32t I think a 44t would come about level with the top of the swingarm and would need some sort of chain slider or maybe a runner at the swinarm pivot, there will also be around 2cm of chain growth over the swinarm travel so a chain tensioner will be required. As I have said Im not going down this route as the chainring will not be driving the back wheel directly. I would imagine that peddle bob would be quite bad tho now I have mocked it up. Anyway here are the pics.

frame4.jpg

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[Lenk42602]

Got the metal I ordered for my swing arm last friday. My original plan was to narrow the CR80 swing arm I had, but it ended up seeming like more of a pain in the arse than just starting with new tubes and getting on with it.
Was off today, so i decided to dig in before my Valentine gets home from work.....

Cut all of the swing arm sections to length.

The BB shell at the front of the swing arm will actually set about 14mm rearward into the two parallel swing arm beams. Should be visible in the pic based on my sharpie marked CAD template..... The actual swing arm pivot will be located about 50 mm above the top of the arms, and about 25.4 mm behind the BB shell. This will all be welded and tie into the beams for strength. I am going to get all of this sorted and square before determining the lower shock mount position and configuration.

Another time consuming step coming up is going to be the dropouts - I plan on using 10-12 mm thick steel plate for my dropouts. Right now, the plan is to section out the inner portion of the tubing on the axle end to accept the dropouts, and then weld those mo fo's in. I wonder if mild plate steel, rather than hardened plate steel, will be acceptable for use as dropouts?

Anyways, with this configuration, I have plenty of crank arm clearance, chain clearance, and a nice straight chain line. I was a bit worried that this swing arm would be too long (and laterally flexy ) end to end, but the reality is that the actual length of the swing arm from pivot point to axle is what counts. The BB shell will just be welded on to the front of the swing arm, and really has no impact on the overall stiffness of the design. I hope.

[Lenk42602]

Well, last week it was 60 degrees here in Pittsburgh, and I actually rode my 29'er pedal bike to work everyday. Sweet. Then we got 8 inches of snow two days ago. Also decided to get my original stealth bike (circa 2008)re-wired and juiced with my 36 volt brushed heinzman setup. Rather lame , but at least I have throttle action to keep my mojo workin'... I may go from parallel to series and run 74 volts ....just to see what happens....

- Back to the bike...
Got the front sections of the swing arm notched out to accept the bb shell.

The gap in the upper section is is a result of the BB laying on the cardboard. Actually much less gap when placed in its actual location..

fitted to the swing arm head

JohnRobHolmes sent the second half of the wheelset custom built for this rig. 16" moped rim, 13 gauge spokes, custom nipples.


Just a note, I have been riding bicycles for 20 years now and am extremely familiar with bicycle mechanics, including wheels. I work in a bike shop. Lacing wheels and getting them straight in a truing stand is one thing, but it takes many, many years (or wheel builds) to understand the aspects of wheel building so that the end result:
1.) is well matched, in terms of strength, to the intended application
2.) not only rolls true, but stays true over time....
I know of two individuals in Pittsburgh that I trust with my my own wheel builds, and that is with conventional, readily available bicycle-specific wheel components. John's approach and execution of wheel building is many degrees higher than most individuals I have come across, including mechanics in bike shops.

Thanks John. You wheel building freak.

Next step is the rear dropouts. I am going to cut some out of thick plate steel and see if I can come up with a system that won't need torque arms. After they are good to go, it's jig building time. Then ,tack the swing arm together, without the shock mounts.

Len

[Lenk42602]

Began drop outs today. Cut two, 100mm sections of 9.5mm flat stock to begin with:

I absolutely need to get the inner facings of the dropout surfaces completely perfect in order for the axle flats on the hub motor to make a strong purchase, maximizing surface/contact area. All in effort to eliminate the need for torque arms. Still working on an integrated clamping mechanism at the drop out..

Len

[Whiplash]

Why not drill and tap the channel vertically so you can run a bolt through behind the axle then tighten it down clamping the axle with the channel? The channel seems thick enough to drill/tap no? Would make a simple but effective solution! Or even through bolt it vertically so you can run a fine thread bolt with better clamping force...

[Lenk42602]

Looks like my pics all crapped the bed...

So here is the second set of drop outs I made up - first set I cut the dropouts too wide , too much slop. That sucked.

Here's the basic form of the dropouts - need to clean up the inside a bit..

hey whip,

think I am going with a varition on that idea - the steel is 9.5 mm wide, so I would have a rough go running a hole vertically through the drop out... going to weld a steel bushing vertically where the file is pointing, and a nut on the lower side. I can run a bolt through and be done with it...

On the wheel:

mocked up near the monster swingarm. going to notch out the arms, then weld in the drop outs...

Plan on tacking the swing arm assembly together by the end of the week. Now I am gonna go back and repopulate my thread with pics....

[Factory Phil]

Len,
Great looking build! Can't wait to see more & how you fit in the batteries.
That front tire also looked great, what size rim was that? Also the tire, what size & make was that?

[Whiplash]

Yeah great idea on the dropouts, not only will the bolt allow you to pinch the axle, it will also keep it from spreading under load... keep up the work!

[John in CR]

Lenk,

Great work. WRT the clamping dropouts it seem appropriate to me add a thin slot in the steel to permit a good clamping action. My concern is that without one the clamping bolt deforms the metal slightly to make the axle impossible to remove without filing to enlarge the slot. I've had a hell of a time getting a motor out of a custom snug fit dropout before, and that was with no clamping. Another benefit is that the axle slot can be to big and the bolt snug it right down.

Here are 2 sets of mine, with hacksaw results, so your bandsaw was a great purchase. I did double up my blades though to make the cut a little wider.

Clamping dropouts.JPG (30.43 KiB) Viewed 674 times

[Lenk42602]

@Whip - build got delayed a bit. I landed a part time gig working in A MACHINE SHOP with an old timer. It has been great so far.. Time to play has just been minimized a bit though....

@Phil - Tires are BMX, 20" X 2.4", these: model IA-2021 - http://www.innovatires.com/menu.php?xCPId=B06
......for now.... pulled them off a kids gt stomper 20" bike at the shop I work in....

The rim is a 16" moped rim, DOT approved. Heavy duty. This gives me the option to run bmx tires or 16" moped/motorcycle tires....

I wont be getting back to the frame until after this swing arm is mostly complete. the sequence planned is swingarm, lower main frame (where swingarm pivot point is) main frame w/out head tube area, then attach head tube area, then shock mounts on swing arm (lower) and main frame (upper). then seat tube.

Good lord this takes for ever. I hope it comes out close to what I am envisoning....

[Lenk42602]

Great .... so your bandsaw was a great purchase.

Clamping dropouts.JPG

It would have been impossible to get this far without. Seems jigging material is the biggest challenge to getting the machine to cut well. Takes all of the sweating out of the equation....

DIdn't consider the slotting idea. makes sense. The drop outs are snug right now, so I will add the clamps prior to the welding phase of the swing arm and determine if I need to slot them..

Len

[Lenk42602]

Back on the horse.....

Got slowed with this build due to a terrible sickness over the last few weeks and work.... I think (hope) the last green caterpillar decided to crawl out of my right nostril this am. No bacon frying yet, but while sick I was able to fit the critical head tube junctures to tight tolerances, as well as notch the rear swingarms to accept the dropouts.

head tube, (top tube frame rails)

drive side swing arm pieces + dropout clamped/magnet jigged together..

We have been in the mid/upper 30's for the last few weeks. This simply should not be at this time of the year in pittsburgh.... Hopefully we will be in bacon frying weather soon.... You may notice the amount of tire clearance, I want to be able to run this size wheel as well as 24" mountain bike rim on the back in the future, so I gave myself some room......

Len

[johnrobholmes]

Just ran across this thread, great build you have going! You do all the dropout work with that band saw? Maybe drill a pilot hole for the rear of the dropout slot? I had been trying to make the same sort with my jig saw, and it just wasn't cutting the thick steel well enough to keep going with the work. In the mean time I think I figured out a way to make a clamping dropout without needing to use super thick stock, but I gotta make it before saying it actually works.

I'm so jealous of those wheels I built for you. Sooooooo jealous. Thanks for the kind words!

[Lenk42602]

yeah john, that little 4X6 bandsaw has been the key to all of the cutting everything parralel, square, etc..

I basically just took the two dropout blanks, clamped them together, put them in the carriage, and then let the saw drop. Then I flipped over the clamped dropout blanks and cut the other side. Had to hacksaw about 3/16" on each side to level them out, and then I used a drill press to round the back of the dropouts. Then the hand filing. More hand filing. Cut the dropouts to 9.28mm, then I hand filed the dropouts the axle sits in so that it is SNUG.

Keep me posted in your dropout clamp idea. I am a little nervous about running a hole vertically through dropouts and then tapping it for a cap bolt. I just don't think I can do so very straight with a bolt large enough to have any clamping force given the width of dropouts. Thats why I am leaning toward the more crude pinch bolt at the back of the dropout idea...


Len

[johnrobholmes]

Mine is more of a sliding dropout/ lollypop/ pinching idea where the pinching body keys into the dropout and also handles chain tension.