Stretching the wheelbase on a trike

[momus3]

My Traditional Sun trike finally arrived, and now I can get started with converting it to an eTrike once I figure out which hub motor kit to buy. The short wheelbase worries me. I'd like to see it extended at least a foot or two to increase stability and add to the carrying capability. I don't have a welder, so I wasn't going to stretch the frame, but I was looking at a cargo bike today that had been stretched by simply bolting on one of those Extracycle add ons.

I'm going to buy another welder (thank you Uncle Sam for the xtra funny money), and it looks like it would be possible to build something like that Extracycle design and bolt it onto the Sun trike. That way I wouldn't have to cut the frame. I saw the trike that DDk made and love it, especially the low slung look and the bigger tyres.

Has anyone else here stretched a conventional trike? There's probably more ways to do this. Sometimes I get one idea in my head and can't see the other possibilities. Not looking to do a complete makeover, just put a suspension fork on the front w/ a disc brake, a hub motor somewhere (On the front? One side of the rear?) and stretch the bike as simply as possible.

 

[donn]

The short wheelbase worries me. I'd like to see it extended at least a foot or two to increase stability and add to the carrying capability.

That would work on a 2 wheel bicycle, but I suspect it could make a 3 wheel tricycle less stable. Depends on where the weight is (i.e., you) - if you stay near the two side wheels, then no great problem, but if you stay forward while the wheels move back, you're now closer to the edge of the triangle.

 

[goatman]

I built a normal trike for my son with a heavy front DD hub motor, if he goes up a bit of a steep gravelly path the front wheel will start to spin and once he starts to pedal, he gets up no problem, like a 4x4, 2 wheels under power/traction.

 

[ddk]

...
I'm going to buy another welder (thank you Uncle Sam for the xtra funny money), and it looks like it would be possible to build something like that Extracycle design and bolt it onto the Sun trike. That way I wouldn't have to cut the frame. ...

If you read about 1/3 the way down in this thread you will notice I stretched the main frame by simply copying the rear dropouts that attach the tricycle rear to the main frame from 3/16" mild steel. I extended mine by 10 inches IIRR. If I were to extend further I would have used square tubing for additional lateral strength.

I thought I noticed the sun traditional trike went with 24" wheels all around?
My Trike came with 20" rear tires and a 24" front. Initially I used a bigger tire that brought the size of the 24" tire to 26", but I eventually went back to the supplied chinese tire (amberwolf knows the manufacturer but I forget the name)

 

[Balmorhea]

My Traditional Sun trike finally arrived, and now I can get started with converting it to an eTrike once I figure out which hub motor kit to buy. The short wheelbase worries me. I'd like to see it extended at least a foot or two to increase stability

Nope. One of the main things that makes a trike squirrelly is twist between the rear axle and the steering axis. If you lengthen it, even with well-designed welded reinforcements, that twist will increase. Try to use a bolt-on solution designed for bicycles, and it will be unmanageable (as well as weaker than before).

Please take my word when I say this: If you don't like the way a Sun Traditional trike handles, you simply don't like the way upright trikes handle. You can modify it, but it won't become significantly better.

This is why my first suggestion to anyone who tells me they want a trike is to ride one for a good while, and see if they still want one.

 

[dogman dan]

I say stretch away all you want. But like said above, make it stiff so it doesn't handle worse. Add whatever it takes to stiffen up the thing, after the initial stretch using a piece of steel like DDK did. If that sun trike is steel, you can even stiffen up the front part using additional struts, somewhat like a mixte bike frame.

This was the basic goal when we made AW's trike, we copied this semi bent for the front frame, then he used an existing trikes rear frame to complete it.

I was there only for the initial build, and the result after one day was fairly flexy as I recall. But it did not ride shitty. Later on AW added enough framework to make it quite stiff compared to the original build.

But right now, I still feel what you need is the correct motor on it, which will result in a very low top speed. 15 mph ideal, but for damn sure nothing capable of 25 mph. Learn to ride the thing as is, then consider modifications. Consider it training, or learning curve.

Bear in mind as well, that nothing will make it easy to ride on the edge of a highly cambered street. So if your routes have a lot of tilt on the pavement, you will have trouble steering at 10 mph. Or you have to ride up the center so you get off that camber. Cornering adult trikes is not hard.. you just have to slow down and not be expecting a 25 mph corner like on a bike.

 

[ddk]

Bear in mind as well, that nothing will make it easy to ride on the edge of a highly cambered street.

the trike i pictured not only rides a crown of the road like a bicycle, but also turns at speed without tipping.

My other trike?
not so much...
actually, it acts like what you described

 

[ddk]

Mr dogguy,

the poster above you added so much false information I don't know where to begin. But begin I will with:
let's have a conversation about some of the real reasons traditional trikes are so 'tipsy'.
On a bicycle we humans (and some monkeys, chimps and orangutans) are playing a balancing act with an inline two-wheeled thingy. This act includes feedback to our bodies as to how far we can take things, like a turn, before everything goes to poopoo.
A trike, being self-balancing, offers no such feedback, so we aren't made aware of 'too much' (until it's 'too late') and since we can turn the front wheel of both bikes and trikes +- 170 or so degrees you know right away not to do those extremes on a bike... and on a trike it's useful for making extreme turns at less than 1mph.

I've owned or ridden only one trike with a 'squirrely' rear and that was because the manufacturer forgot to insert the bearings in the rear wheels!
(too much fun in my life)
...and I can't think of any traditional and non-traditional delta trike that doesn't use a bolted-on rear end to a chopped bicycle frame. And I've ridden all the Sun's offerings. Yorks (whattheheck happened to york?) Belize and several other brands but never a Schwinn.

the end

 

[donn]

let's have a conversation about some of the real reasons traditional trikes are so 'tipsy'.
On a bicycle we humans (and some monkeys, chimps and orangutans) are playing a balancing act with an inline two-wheeled thingy. This act includes feedback to our bodies as to how far we can take things, like a turn, before everything goes to poopoo.
A trike, being self-balancing, offers no such feedback, so we aren't made aware of 'too much' (until it's 'too late') and since we can turn the front wheel of both bikes and trikes +- 170 or so degrees you know right away not to do those extremes on a bike... and on a trike it's useful for making extreme turns at less than 1mph.

If Mr. dogguy objects to this account of the difference between bicycle and tricycle riding, he's not the only one. Starting with the way a bicycle rider turns the wheel, in actually the opposite direction.

 

[dogman dan]

No objection.

But to clarify, I have found trikes I have ridden to pull to the downhill side of a crowned road. But how bad depends on both speed, and the slope of the crown. City streets in general, have a moderate crown and you simply steer up it a bit. No big deal, even at 25-30 mph. But a county road with a deep ditch on the side can have a very steep slope on the shoulder, the "bike lane". Easy to solve, simply slow down to below 15 mph. Or take the lane on a 55 mph road.

What you don't do, is move out of the lane onto that shoulder at 30 mph.. Hello ditch.

Again, if you ride a trike a lot, DO master the low speed, say 10 mph or less, two wheel turn. It will teach you where that point is. You may need it in a pinch someday. Definitely nice how tight you can turn a trike at sub 5 mph. Way tighter than you can typically turn a bike, unless you have feet on the ground.

But all this discussion is a bit like how many angels on the head of a pin. Those tall schwinns, suns, and worksman trikes don't handle all that shitty. Flipping one is rarely a hazard, at all. But just don't try a 30 mph turn to avoid a tree, or dive onto that steep shoulder at 30 mph. If you build one to go faster than 15 mph, learn where the limits are and respect them. Not much different than any vehicle. it has limits, and you need to feel them out before you try it at speeds that are faster than normal for the design. Learn when your wheel lifts, and what it feels like, and how you steer to put it back down. Then you have no problems.

 

[donn]

Again, if you ride a trike a lot, DO master the low speed, say 10 mph or less, two wheel turn. It will teach you where that point is. You may need it in a pinch someday.

Now I'm wondering, why not? Rather than put all the effort into engineering it so that all 3 wheels stay on the ground, design the tricycle so that it's manageable on 2 wheels and assume that's going to happen in turns.

I expect with a typical wide design, steering is pretty wacky on two wheels, with the front wheel at 45° to the road or worse. So it's great for the vast majority of the time, but very badly messed up when the curve is too hard. The narrow 2/3 design would probably be kind of rocky much of the time, take some getting used to - but great in curves. OK at slow speed turns, better clearance in bike lanes.

 

[momus3]

Wow, that is one beautiful trike dogman dan. I am impressed. Probably the most stable and stylish example I've ever seen. Great design and workmanship. Looks very modern and low slung compared to what I will be riding.

Thanks to everyone for all the good advice. I'd never even considered frame twist. That should be easy enough to address now that I know about it, and I don't care if the trike weighs a ton as long as the weight is low. I'll probably go w/ a front hub motor to simplify things even though I would prefer rear drive. Can always go that route if I don't like the puller action.

Yes, this Sun trike model is steel. That's what you get at this price point, and that's fine w/ me because I can't weld aluminum anyway.

 

[amberwolf]

Wow, that is one beautiful trike dogman dan. I am impressed. Probably the most stable and stylish example I've ever seen. Great design and workmanship. Looks very modern and low slung compared to what I will be riding.

I don't see any trike in his posts? Just a semi-recumbent bike?

Which trike are you referring to?

Has anyone else here stretched a conventional trike? There's probably more ways to do this. Sometimes I get one idea in my head and can't see the other possibilities. Not looking to do a complete makeover, just put a suspension fork on the front w/ a disc brake, a hub motor somewhere (On the front? One side of the rear?) and stretch the bike as simply as possible.

Have you looked at my SB Cruiser trike thread? It's quite an evolution there, that might give you ideas you've never thought of.

There's also the Delta Tripper trike, which was cannibalized to make the SBC, that has many ideas in it. (but as finally implemented is very tall for it's wheelbase and width, and very very tippy, earning it the nickname "Delta Tipper")



BUT: whatever you do to yours, it's still a trike...and it still has limitations, especially when designed like the one you're starting with, and without some radical changes is unlikely to be stable / "safe" above 10-15mph, and much less if you're turning.


This was all discussed in the other thread already, but I'm not really sure how much you've taken in from that.

Keep in mind that many of us are speaking from *direct experience*, and not from theory.