4-stroke gas scooter build

[CI]

The total sprocket ratio from the motor sprocket, through the jack shaft, and to the rear wheel sprocket is 8:1.
The go-cart site has a nice speed ratio calculator.
The target speed is about 3 mph at 800 rpm.
I will have to find out if an rpm that low will give the motor sufficient torque, else I may have to use a different sprocket ratio.

I will probably tack weld the motor mount and jack shaft supports, and take it for a test ride, just in case things need to move around a bit.
Measure once; verify; and then weld permanently once.
Luckily steel if very flexible material, and can be relatively easily cut, bent, and welded to make adjustments.

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[CI]

Work continues on the 4-stroke scooter.
I got the steering head (I forget the formal name for this item) machined for sealed ball bearings top and bottom.
I tack-welded this piece on, but them forgot my phone inside when I went in, so no further photos, although I have made more progress.
Lets hope I got the angle correct.
Much of this is uncharted water stuff.

I got the front forks fabricated.
It is raining today, so my welding work has been stalled.

I am using modified go-cart parts for the most part, and so I am basically making up the design as I go.
Sort of a function over form affair at this point.
Refinement can come later after I have a working scooter.
This will be scooter prototype No.01.

I would like to cast some aluminum rims, but no time to 3D print patterns for that now.
I can't find any cast rims for 4.10 x 3.50 - 4 tires.
Cast rims are available for larger tires, but I want to stay with a 10" diameter tire.

I found some handlebar levers.
I did not have any 7/8" tubing for handlebars, so I ordered a piece of that.
Standard pipe sizes come close to being usable for handlebars, but I need the grips and levers to clamp securely, so I need exactly 7/8" diameter tubing.

The chain was shipped with a thick oil on it, and what a mess it is to handle that.
I have a jackshaft for speed reduction, so I will have two chains to keep in adjustment.
I am contemplating using fan belts in lieu of chains, but will leave that to a later refinement phase.

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[Johnmcc69]

Looks like a fun project!

 John

[CI]

This has been a fun project, but also something I really need as soon as possible.
My electric scooter is plagued with flat tires for some reason, and they are almost impossible to change, due to the motor being built into the hub, and the small clearances between the tire and rim.
I do like getting out in the morning, since often that is the only time I will go outside.

My wife runs in all weather, including snow, ice, etc. (this scooter is to accompany my wife while she runs), and so I purchased some snowmobile pants, gloves/mitts with pockets for hand warmers, scarf which covers most of the face, wool hat, etc.
Last year we had some 18 F mornings, and I was comfortable with all of my gear on, and three hand warmers in each glove.
The only problem with the really cold weather is that the equipment tends to start locking up.
Last year on a cold day, my throttle stuck wide open, and the electric scooter did a huge wheelie.
I had the prescence of mind to hang on to the handlebars at all cost (an old dirtbike riding habit), and manually push the lever-throttle closed.
My wife looked at me like "what the flock are you doing ?", LOL.
Life comes at you fast some days.
.

[CI]

I ground the welds on the forks and sanded them.
I am not keen on the stress that will be on the end of the 5/8 inch rod, but no time to redesign at the moment.
This is not a high-speed scooter anyway, but I think a tube design would be better than the rod that I used, as far as resisting breakage.
I considered a motorcycle-style front end arrangement, with dual fork tubes and clamps, but I am trying to go as minimalistic as possible on this build, and also keep the weight as low as possible.
The steering column will fold down so I can transport the scooter in the car.

Note, the first photo shows the wheel and fork inverted, just as a way to support these items, to take a photo.

I am not too concerned with aesthetics on this scooter, but I also don't want a "franken-scooter" look either, so I am sanding things out.

At some point (not now), I would like to convert to a mono front fork and rear swingarm design, and carry a spare tire/rim, so I can change a tire if it goes flat.
I have enough rigidity in the frame to use a mono design, I just don't have the time to design it.
I need to verify that I have a functional geometry and drive train before I get too far into it a design.

.

[CI]

I was going to install the jackshaft up higher, behind the motor, but the chain appears as if it will strike the oil fill cap.
I lowered the jackshaft, and I think that position will work ok.
I cut the front chain first, with the motor as far back as its mounting slots will allow.
I cut the second chain to length, keeping in mind that the rear axle has to be able to move towards the rear for chain adjustment.

Things seem to be working out ok, so far.

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[Minh Thanh]

 Interesting !!!! 

[CI]

Thanks Minh, it has been pretty fun so far.

I was concerned about my steering shaft being too small (5/8" solid shaft), and when I started thinking about how I was going to attach the stem, and how I would have to clamp the entire assembly and tighten it, plus add a pin through the steering shaft, I decided to redesign the entire steering head assembly.

I cut the 5/8" rod off of the forks.
I found a spare axle stub which had a threaded end, with slotted nut, and a hole drilled for a cotter pin to lock the nut.
I cut the axle off short.
I welded the axle stub onto a length of 3/4" shedule 40 pipe, which is 1 inch diameter, and then welded the pipe onto the forks.

I turned some bronze bearings, and will press those into place in the head tube.

This steering assembly has a much more solid feel to it, but is still relatively light, since most of the shaft is hollow pipe.
The threaded nut on the top of the shaft will allow me to tighten the assembly, and the solid threaded shaft is large enough to allow me to drill a 1/4" pin hole, to pin the stem to the top of the shaft, so that the stem rotates with the steering shaft.

A steering assembly is more complex than I was thinking, such as my design where the forks don't extend upwards to a top yoke.

I have confidence that this steering shaft will not fatigue and break over time, and the handlebars and stem will remain in place, pinned, and secured by the large nut.

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[CI]

One more photo.
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[CI]

The front hub is about ready.
I still have to turn it for the sealed bearings.
The front axle will be dead-style, and the rear axle will be live go-cart-style.

I added a few braces for the steering head.
Probably not necessary, but better safe than sorry.

And I got the handlebars bent into shape, and am installing the levers, kill switch, etc.

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[CI]

I got the front hub finished, assembled the tire, rims, and tube; and pressed in the two sealed ball bearings.
Aired the tire.
The front wheel, hub, forks, and steering tube are complete, and ready.
I need to make a stem, and a hinged tube to go up to the handlebars.

Assembled the rear tire, rims, tube, and hub, and aired that tire.

I welded some angles onto the rear axle bearing brackets, so that I can slide the rear axle rearward, to tighten the 2nd chain.
The engine will slide forward to tighten the 1st chain.
The jackshaft will be in a fixed position.

I always wanted a TIG machine, and that would save me a lot of tedious grinding, but I would not use it enough to justify the cost, so that is not in the cards for me.
No space to add a machine in my shop anyway.
I would like a tombstone Lincoln AC/DC welder, but the prince for one (like many things) has gotten out of reach for me.

Making progress.
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[vtsteam]

What kind of welder do you use? 

[CI]

I use the trusty old $100 (when purchased) tombstone Lincoln.
It always works, and while it does not produce the best looking weld, it will produce a solid weld.
I extended the leads on it about 10 feet.
Rods are standard 6011.

Part of the sloppy look of these welds is that they are often out of position, and also in some cases, a thinner piece welded to a thicker piece, which tends to try and punch through the thinner piece if you are not careful.

My dad had an ancient large Lincoln with the crank on top, and it was AC/DC, and with a good DC rod, and the correct polarity, welding was infinitely easier, and a smoother weld surface too.  That welder had about a 30" square footprint.

My Lincoln goes for perhaps $600 now, and the AC/DC model is well over $1,000.
I have more time than money at this point, and so I just grind the welds down.

I have used a MIG before, but I have used a stick welder for over 60 years, and so no sense changing now, especially for that price.
I would hate to think what a good TIG would go for these days; I would not buy an off-brand.

The key to a strong weld is using the right gap between the pieces.
It may not look pretty, but with the right gap and heat setting, you can get full-depth penetration, and the weld will be strong.
This scooter does not need to win any beauty awards, it just needs to work in a reliable fashion.

Edit:
One time I tried some rods that had metal filler in the jacket, for horizontal use only.
They created a very smooth weld that looked great, but I had a weld fail, and so I never used that rod again.
The high-fill rods create a superficial weld that does not have full pentration.

The 6011 is agressive enough to melt down to the backside of the metal being welded (with the correct gap), and is an all-position fast-fill rod too, which is handy.
I have never had a 6011 weld fail.
.

[vtsteam]

I have a Lincoln tombstone, too. But it cost me about $200 back in 1996, I think. I also extended the leads, like you.

I see people have added DC w/ a full wave rectifier of enough capacity, plus heat sink, and a choke -- here's a dude doing a dude level job of it. I'm sure with your background you probably could do better, but you get the idea:

<a href="https://www.youtube.com/watch?v=NpVj6QLwHlU" target="_blank">http://www.youtube.com/watch?v=NpVj6QLwHlU</a>

[CI]

I have looked for a turn-key stand-alone DC module for a welder, but have not found one yet.
I found this discussion on a forum.
Sounds like it can be tricky to get the diodes to share the load equally, and they will overload and burn out one at a time, according to one person's post, if not set up correctly.

https://forums.yesterdaystractors.com/threads/converting-an-lincoln-ac-welder-to-dc.937685/

Here is another interesting site:
I would probably not attempt to add DC to my tombstone, unless I could find a turn-key plug-in box that had a good reliability record.

The beauty of the AC tombstone is that like the energizer bunny, it keeps going, going, going.
There is not much to break on them.  I had a little trouble with the amp selector switch snagging on one tombstone I had, but otherwise no problems.
The welding examples on the site below are not that impressive for DC welds, in my opinion.
I recall the DC welds I made being very smooth and even, and I was not very good at welding when I used it.
As I understand it, polarity is important when welding with DC, and one polarity works a lot better than the other (I forget which way works better).
And the rod manufacturer is critical for good welds too.
I bought some big name welding rods from Norther Tool (I won't mention the brand, to avoid a lawsuit), and while I had never had trouble welding before, these rods were unusable, and I had to toss them in the trash.
I went to a welding supply house, and told them I needed a good AC rod, and they sold me a brand (I forget the name), and they weld very well.

https://www.hildstrom.com/projects/2009/01/ac-225/index.html