Jml Colorado

Rake and Trail assistance for a trike

22 posts in this topic

Hey folks!

Got myself s fun little project. Building a trike. I was going to cut the neck and rake the bike a bit more, but I looked at what it has for trail before welding everything together and found it has a pretty excessive amount with the current setup. It looks to have a 7 5/8" trail.

I hear that for a trike, trail should be more like 3-4"? Is that correct?

The way it lok,s right now, I'll need to find some different forks that have the axle mounted on the leading edge. This should reduce trail a little bit. Then shortening the forks and removing some rake would help as well, right?

I have already shortened the internals on these forks 2" and also slid the tubes through the tripples about 1 1/4" as well. I really cant get much more out of these forks.

Any ideas?

It's hard to see here, but I have a string running in the center line of the neck, all the way to the floor.

photo-415.jpg

The level shows centering of the front axle.

photo-995.jpg

The vice grips are just holding the string right at the center line of the neck.

photo-2215.jpg

And here is the trail number.

photo-207.jpg

Edited by Jml Colorado

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I decided to run the numbers through a rake and trail calculator and found my string wasn't in the exact right spot.

Here are the numbers:

Front tire-26.75"

Rake-43* (I know, that's a lot)

Tripple clamp offset-2 1/4"

Fork legnth-28.5"

Triple tree rake-0"

Total trail- 9.4"!!!!!! WOW!!!

Next, I punched in to see what I could get the trail to if I built a set of tripple trees with a larger Tripple clamp offset. I found that 6.5" got the trail to 3.58". Now THIS is a workable number.

I could also make raked tripple trees, but that would require absolute precision on a mill, which I have access to, but I'm not that skilled on it. It would be much easier to build a normal set of tripple trees with straight holes for the fork tubes, but with a larger offset from the neck stem to the fork clamps.

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Build a pair of triple trees longer on bottom and shorter on top. Or get some really wide bars so you can overpower the incredibly heavy steering.

Dusty.

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Build a pair of triple trees longer on bottom and shorter on top. Or get some really wide bars so you can overpower the incredibly heavy steering.

Dusty.

If I built trees like that, wouldn't I have to drill the tube mounting holes at an angle? Say, 5* to make the forks rake more then the neck?

I'm not sure how accurate I could do that on a mill.

I guess I could weld the two blank plates together that I'm making the trees with, then weld a piece of scrap under them so I drill 2 continuous holes through both at the same time.

That way, once I seperate the two, all four tube holes are drilled at 5*, then just make the bottom one longer from center of the fork mount and the stem.

It almost seems easier just to drill square holes and offset the stem and fork mounts 6.25" to get the same affect.

What are the advantages/disadvantages of each?

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I had researched vw trikes and there it is said that a lot of trail is ok. But them guys are very light on the front wheel. I built mine with six inches of trail. It is very stiff on my front engined trike. I am currently building a leading link fork to reduce trail to one inch. I would not recommend living with a lot of trail on a trike with a front engine. Leading links and girders seem to be the best alternative.

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I had researched vw trikes and there it is said that a lot of trail is ok. But them guys are very light on the front wheel. I built mine with six inches of trail. It is very stiff on my front engined trike. I am currently building a leading link fork to reduce trail to one inch. I would not recommend living with a lot of trail on a trike with a front engine. Leading links and girders seem to be the best alternative.

I'll look into a girder setup. It might be more beneficial to go that rout and get the trail right where it needs to be that way anyways.

On the plus side, this trike, 90% of the riders weight will be over the center of the axle and the engine is only a 350 so there isn't too much weight.

Since I'm still up in the air about it, I might try it with the trail where it is now, with the expectation that's it's crazy bad, and if it is, then build a girder at that point.

From what I understand, trail for trikes should be between 3-4". Is that right?

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Well mine is the only one i have ever built. But now knowing 6 inch is way too much i have looked into trikes that are more simular in balance and weight to what mine is. I have seen where a converted wing has to much trail for a trike. I do not know first hand yet. But they use raked trees on a wing and reduce the trail to around one inch. As i understand it now that it dont lean in the corners it now needs trail numbers like a car (castor in car terms). I am building mine at one inch, if it dont work out i can change the length of the leading link.

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And yes mine has gotta be a good bit heavier than yours. I have around 250 pounds on the front wheel. The stiffness might not be that bad on a light bike. I have a stroked vw motor in the front of mine.

Jump over to the trike thread and read through the pinned threads. A lot of good info there that i wish i knew when building mine.

Edited by DeathBySnuSnu

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And yes mine has gotta be a good bit heavier than yours. I have around 250 pounds on the front wheel. The stiffness might not be that bad on a light bike. I have a stroked vw motor in the front of mine.

Jump over to the trike thread and read through the pinned threads. A lot of good info there that i wish i knew when building mine.

Wow! Castor like a car? Now we're talkin in fegrees rather then inches!

Thanks for your input. Food for thought for sure.

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Yes you are correct. Caster is expressed in degrees. For example my little chevy truck is two degrees. Convert that to trail and it is about half an inch. I think one inch is a safe number for a trike.

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Thinking of building a leading link setup. So now the question is, what size DOM would be the best.

I need 1 1/4" if I plan on using my stock trees. With that said, .250 wall seems pretty solid. The legnth would be under 36". More like 30" total. To keep this a cost effective as possiable, I'd like to use a material that surpasses the requirements but it exceed that too much. I could bump up to .375 wall but the cost increases substantially.

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I think that the ones that get away with 6 or 7 inches do so because they have 3 feet or more of handle bar leverage.

I would think that .125 wall thickness would be fine in either RWS or DOM.

Even though I prefer Girders a Springer would make it easy to change the trail.

Dusty

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I think that the ones that get away with 6 or 7 inches do so because they have 3 feet or more of handle bar leverage.

I would think that .125 wall thickness would be fine in either RWS or DOM.

Even though I prefer Girders a Springer would make it easy to change the trail.

Dusty

.125 wall? Really? Man, that seems thin for this application. Maybe I underestimate the strength of DOM :)

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My Finch springer is .250 wall (1.25" OD without going out and measuring...lol) and it flexes @ 45* rake, no way would I trust my life to .125".

And DOM all the way for forks (or frames for that matter) IMHO.

Seams split especially if the designer/builder places the seam in the wrong plane.

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My Finch springer is .250 wall (1.25" OD without going out and measuring...lol) and it flexes @ 45* rake, no way would I trust my life to .125".

And DOM all the way for forks (or frames for that matter) IMHO.

Seams split especially if the designer/builder places the seam in the wrong plane.

A spriger is a way different animal from a girder structurally.

1" 1020 steel tube .125 wall 72 years of use and abuse made years before DOM was available.

post-12692-0-25643200-1348419346_thumb.j

Dusty

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I am building my leading link also. I lathed down stainless steel seamless. It left me around .200 wall. Mine are short and not super steep on the angle.

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My Finch springer is .250 wall (1.25" OD without going out and measuring...lol) and it flexes @ 45* rake, no way would I trust my life to .125".

And DOM all the way for forks (or frames for that matter) IMHO.

Seams split especially if the designer/builder places the seam in the wrong plane.

Were not building LSR's or drag racers on here. I'd build something like your springer and eat the weight instead of taking chances of eating pavement.

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So here's my next question.

Since I'm building my own setup, what is best to use for bearings in the rockers and other misc arms? Should I precision drill the rockers and install bronze bushings, Or would a bearing of so,e sort work?

Edited by Jml Colorado

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Bushings. Specially if you can get some alumabronze.

Edited by LeeRoy

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Oilite bushings and it's good to have a means of greasing them.

On my rockers there is a groove machined around the middle of the bushing and there's holes in the bushing that let grease lube the wear surfaces. Small grease fitting and you're set.

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more than 3.5" of trail is no good on a trike.On dirt roads that is the number i would use but i would bring it down to 2" if its all street riding.The more you rake a trike the uglier things get.years ago some of the old makes had girders that had 2 sets of holes for the arms so you could set up a better steering bike when you throw a side car on it.A girder is the way to go here but finding the rite shock sucks.Also a girder can make you bike look longer with less rake.You are better off using dom or erw for them also.Some guys like chromoly but is more likly to break were the lower carbon steels will give you some warning by bending.On your bike i would use 1 1/8" erw or dom(.120") and it would be super solid(actually overkill).springers require thicker steel in the rear leg because it is supporting and keeping everything else strait,totally different animal than a girder.Another cool thing is very few people run girders because the really need to be set up for every bike different were a springer you can change the rockers to get better trail specs within reason.

Edited by paintmegone

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