Delta trike design- For under seat steering-

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Jul 8, 2022
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Sagle, Idaho USA
Hey guys and gals- Question- I'm changing my delta trike from a top side cable - to cable under seat steering arrangement. But with Under seat steering the range of motion lock to lock is limited by the width of the seat and the inside distance between the handlebars- On this prototype right now it's about 90 degrees total or 45 degrees either side of straight ahead. And I noticed that with my previous arrangement the steering could be cranked over hard and if you missed your knees with the end of the handlebars you could get turned around in about double the length of the trike, so that is what I'm shooting for again with the under seat steering. If anyone has any good pics of such an arrangement, I would be very interested to see them or any ideas would also be welcome!
 
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Don't forget that you can ratio the leverage between the bars and the forks by having differing link placement lengths from the pivot at the two places. ie 45 degrees fore and aft at the bars doesn't have to mean 45 degree fore and aft at the forks.
 
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Thanks for the reply! And yes I know the ratio can be changed. But since I am running cables instead of a push rod steering system, and I have already had a successful ratio set up with a system similar to a soap box derby car. But the problem was that the steering tube height and angle was not very ergonomic and I would often scrape my knees on the handlebars or the steering tube itself. I thought of cutting the steering tube to re- weld it into a higher position, but my hands already get tired at the height I have it at now. So I thought I would re-design the steering but use the front third of the cable system that I had already built. The potential problem is that there will be insufficient range of motion if I use the same ratio as before because the handlebars do rotate into the seat frame at the limits of travel. So far I have kept the same ratio on my handlebar "pulley" as I had originally, and the steering tube pulley is still the same one I have been using for years. The ratio here is about 1.25 to 3 and it will turn the bike around in about a 15 foot circle if you drop one knee and crank the T bar over to a vertical position. The front wheel goes to almost 90 degrees with that system, although you have to think it through to keep your knees from scraping the underside of the handlebars or the steering tube.

The biggest reason I chose the 1.25 to 3 ratio was to stop the trike from going into a violent head shaking situation when going downhill fast on a bumpy section of the bike path. The ratio used to be 1:1, but changing to the slower 1.25 to 3 ratio was the solution to that problem and the stability of that ratio is amazing. The trike feels like it is "on rails" at any speed that I am ever likely to ride it.

So I am wondering - is there some formula or calculation that can be used, or at least a minimum turning radius that the pushrod steering trikes can easily attain with a known set of dimensions ?

It would be a lot of work to modify the head tube on this bike only to find out that that change was not something that I would end up being satisfied using. I'm mostly concerned that the pushrod will stick out too far to the left side and interfere with my big feet or get bent easily.

Are you running a delta recumbent yourself?
 
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Popshot-

That's very interesting- did you build your own?
How do you like it?

What kind of steering does it have?
Do you have a bike path to use, or do you ride on the street?

I have a hundred questions on that subject- I might build a tadpole for my next project! I'm scrounging parts as fast as possible. There is a bike shop in a town not far away that has a "free" bikes rack and I visit often. The hubs for a tadpole are the thing that's the hardest to get cheaply.

I have a metal lathe, Milling machine and a mig welder, but still no real brazing skills- working on that!
Thing is now I'm 73 and the old "frame" is getting stiff in the wrong places, so I hope to live long enough to build a tadpole and try it out.!!!!
 
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Joined
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I've built many machines. Most are, or at least were, detailed on here. Some will have been lost to the forum change. The only type of steering I don't use is direct into the head tube on a tadpole. I briefly tried it and hated it as it just fely awkward and wrong. USS or tank steering are both good and my latest tilter uses caster steering. There can't be more than a small handful of trikes using caster steering in the world. I ride on roads mainly. Tadpole hubs start around £15 each in Europe but you can use BMX wheels with 14mm axles to avoid that. Not many folk braze these days. The MIG is fine for anything bike or trike related.

If I ever build a delta it will likely be a Mosquito type.
 
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Apologies to the OP tillerman6 but just wanted to ask Popshot a quick question. You mentioned the forum change and I have been looking through the archived stuff on 'the way back machine'. There are some really interesting sounding threads there but only about half of them will click through to anything and almost none of them seem to allow viewing of any pics. Is there another source for old AZ forum topics as I'd really like to be able to see these historic threads and the ingenuity contained in them.

Thanks
John
 
Joined
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Messages
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Location
Sagle, Idaho USA
I've built many machines. Most are, or at least were, detailed on here. Some will have been lost to the forum change. The only type of steering I don't use is direct into the head tube on a tadpole. I briefly tried it and hated it as it just fely awkward and wrong. USS or tank steering are both good and my latest tilter uses caster steering. There can't be more than a small handful of trikes using caster steering in the world. I ride on roads mainly. Tadpole hubs start around £15 each in Europe but you can use BMX wheels with 14mm axles to avoid that. Not many folk braze these days. The MIG is fine for anything bike or trike related.

If I ever build a delta it will likely be a Mosquito type.
Popshot- I will look for a "Mosquito" type delta- very new to this forum, so bare with me if you can.
Progress today- got the cable steering hooked up to my original size pinion steer tube (under the seat) but alas it could only move the front wheel about 3 inches either side of centerline, so tomorrow I'm going to try hooking the cables to the cross arm tubing. That will give me much more adjustabiity as far as range of motion for the limited space under the seat. Who knows it may even work! I still need to scavenge some seat stays or something similar off one of my junk frames and re- weld them into the frame in a way that will clear the under seat steering much better than what I had originally. I really want the ability to turn the front wheel to nearly 90 degrees if that is at all possible with under seat steering and still not have a twitchy bike at speed.
This may cause me to go back to a soap box derby type situation, but once you have ridden a delta trike that has a live axle, 2 wheel drive, and turns almost in twice it's own length, you are hooked!

It's fun to tinker, but I'm not riding anything in the meantime, so it's also frustrating to have the trike "down" until the mods are done..

Brazing- I would never be using this method normally, but when the tubing is very thin, the brazing method (or silver solder) is much more forgiving to the parent material. it does not eat into the tubing wall like a mig welder. In addition, the parts can also be dis- assembled if necessary without losing any of the joint material. A tig machine is still out of my price range as well as having to learn an entirely new skill from scratch. So for now I'm going to look into brazing a lot deeper.

I really cut my teeth on soldering, but the only close cousin to that is silver soldering and that may turn out to be the ultimate solution. I have to find out if Mapp gas alone can do silver soldering or do I really need an Acetaline rig.? The brass/bronze does not really have an afinity for steel as far as I can see at this very beginner level. Time will tell. What I do know is that the joints have to fit extremely close and the material has to be pristine clean for any kind of silver soldering so that the silver will wick into the joint. This is a sight to behold as the fillet is automatically created in the process and shines like mercury when it is flowing. Very little cleanup is needed afterwords, plus the joint is very very strong.

You were saying that hubs for a tadpole trike are fairly inexpensive in Europe? Can you show me a link? I can forgo the disk brakes, but it might be a nice option if the price was reasonable.

I built my own hubs from billet aluminum bars for the Delta trike I'm working on now. Each hub has a sprag clutch and a normal ball bearing. I run a live tubing axle and this creates a two wheel drive trike. But a trike hub can be much simpler and smaller, so it would reduce the cost and weight considerably. All three wheels are 700 C, but the rear axle carries most of the weight, so the tires on the back are something like a 45mm diameter whereas the front is a 25 racing tire.

I would like to see all your creations if possible. It's a shame that some have been lost to the machinations of the digital world. Many of my photos have met a similar fate.
 
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John
Brad would be the man to ask that question. As well as the owner he also hosts the forum and website so will have definitive answers to such questions.

Tillerman6

Use a 15 to 12mm adapter and M12 bolts

 
Joined
Jul 8, 2022
Messages
94
Location
Sagle, Idaho USA
Popshot- I will look for a "Mosquito" type delta- very new to this forum, so bare with me if you can.
Progress today- got the cable steering hooked up to my original size pinion steer tube (under the seat) but alas it could only move the front wheel about 3 inches either side of centerline, so tomorrow I'm going to try hooking the cables to the cross arm tubing. That will give me much more adjustabiity as far as range of motion for the limited space under the seat. Who knows it may even work! I still need to scavenge some seat stays or something similar off one of my junk frames and re- weld them into the frame in a way that will clear the under seat steering much better than what I had originally. I really want the ability to turn the front wheel to nearly 90 degrees if that is at all possible with under seat steering and still not have a twitchy bike at speed.
This may cause me to go back to a soap box derby type situation, but once you have ridden a delta trike that has a live axle, 2 wheel drive, and turns almost in twice it's own length, you are hooked!

It's fun to tinker, but I'm not riding anything in the meantime, so it's also frustrating to have the trike "down" until the mods are done..

Brazing- I would never be using this method normally, but when the tubing is very thin, the brazing method (or silver solder) is much more forgiving to the parent material. it does not eat into the tubing wall like a mig welder. In addition, the parts can also be dis- assembled if necessary without losing any of the joint material. A tig machine is still out of my price range as well as having to learn an entirely new skill from scratch. So for now I'm going to look into brazing a lot deeper.

I really cut my teeth on soldering, but the only close cousin to that is silver soldering and that may turn out to be the ultimate solution. I have to find out if Mapp gas alone can do silver soldering or do I really need an Acetaline rig.? The brass/bronze does not really have an afinity for steel as far as I can see at this very beginner level. Time will tell. What I do know is that the joints have to fit extremely close and the material has to be pristine clean for any kind of silver soldering so that the silver will wick into the joint. This is a sight to behold as the fillet is automatically created in the process and shines like mercury when it is flowing. Very little cleanup is needed afterwords, plus the joint is very very strong.

You were saying that hubs for a tadpole trike are fairly inexpensive in Europe? Can you show me a link? I can forgo the disk brakes, but it might be a nice option if the price was reasonable.

I built my own hubs from billet aluminum bars for the Delta trike I'm working on now. Each hub has a sprag clutch and a normal ball bearing. I run a live tubing axle and this creates a two wheel drive trike. But a trike hub can be much simpler and smaller, so it would reduce the cost and weight considerably. All three wheels are 700 C, but the rear axle carries most of the weight, so the tires on the back are something like a 45mm diameter whereas the front is a 25 racing tire.

I would like to see all your creations if possible. It's a shame that some have been lost to the machinations of the digital world. Many of my photos have met a similar fate.
Popshot- That Mosquito design is rather involved and I am still at a loss for how the steering works, but I'm sure you could pull it off if anyone can. It would be interesting to see how it works, but I will not live long enough to ever build one myself.
 
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The trapezoid holding the seat at the rear pivots at all 4 corners. This pivoting action points the seat and front wheel one way or the other to provide steering fixed with tilt. The pivoting is controlled by wires from the bars to the trapezoid. Not the simplest of builds and the cable steering is sub ideal.
 
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I think I will have to forgo building one of those. I suppose it has it's purpose, but looks like mostly for setting records and where time and expense is not a factor. In the meantime, I'm scouring the internet for pics of the different arrangements for under seat steering or OSS steering by cables. My thinking is this: If it's good enough for a light plane, it's good enough for my trike.

Progress-/more work needed- Since my design is a one off, and I am the only one in the world with a Delta trike like this one, it takes some trial and error to locate and fabricate everything in it's proper location while still ensuring that there are no hiccups along the way. I can't just copy someone else's work or work off a set of plans.

Steering cables hooked up again! Today I installed two turnbuckles into the cable system so that it could be fine tuned and tensioned properly. That was really needed to get the front wheel and the steering crossbar synchronized. That worked well, but I noticed that the cables were getting tighter at the extreme edges of travel. This was caused by my failure to support the centre pivot bolt on both the top and bottom ends.
This caused the pivot bolt to bend slightly towards the front of the trike, and this in turn caused the top end of the steering bar pivot to move side to side. I believe this is what was causing the cable loop to change tension as the handlebars were swung side to side.
I also noticed that the mounting holes in the tack welded prototype frame were drilled off center and leaning to the front slightly. So tomorrow I will correct all that and if I have time I will also install the replacement frame members that brace the seat frame to the main spine. This new bracing should provide more clearance for the USS handlebars to swing and possibly increase the travel limits side to side.
 
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You can make a combination. If you put the cables on a part and let the handlebars go there, you can change the ratio with that part. So you can also make tank handlebars.
 
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