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Old 05-05-10, 05:55 AM   #1
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Make a trike! Technical issues to discuss: two wheels on same axle, driving, braking

Hi people,


I was going to buy a trike from Germany, because here in Finland they're just so effing outrageously expensive. I need it for safe winter riding and for hauling groceries.

I realized, by seeing some bicycle to tricycle conversion kits, that I could convert a beater frame into a trike with a bit of mumble mumble and few spare parts.

One result of the mumble mumble is that I realized I need wheels/hubs with full axles (not QR-type). I am fairly sure I could get a pair of used 26" rear wheels with bolt-on axle hubs.

Now, I have two options: have a long solid axle common to the two hubs, and freely rotating. In this case, I should have a cog/freewheel/sprocket on each hub, and drive them separately in some way. Doable, but complicated.

The other option derives from the previous one: same as before, but the axle is not rotating in the hubs: the cups are somehow jammed (remove the ball bearings and replace them with some kind of washer(s) and/or bolt. The axle would then be rotating inside a couple of cartridge bearings on which the rear cart and rear dropouts would rest. In this case I would only need to drive this axle. But how do I mount a freewheel on it? And how about a discbrake rotor?

Also, any random thoughts that come to your mind, please share. BTW, I am determined to do this myself and not buy a ready conversion kit. I know some will feel the urge to say "just buy this existing kit". I am not going to spend $450 on this kit (cheapest quote with shipping, not even including customs and taxes).
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Old 05-05-10, 06:12 AM   #2
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Most trike kits use live (spinning) axles, which means that the hubs must attach directly to them rather than have bearings. Otherwise the axle would spin in the hub and you wouldn't go anywhere.

Typically the drive is at the center where there is usually an open cross-brace where one or both axles come in and the drive sprocket is mounted. A common arrangement is to use a dummy hub so that standard cassettes and RDs can be used, then a short loop of chain to the axle sprocket. The long trike axle spins on bearings within the adapter and the wheel hubs mount on outer ends.

Visit this site for an idea of how they look.
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Old 05-05-10, 06:29 AM   #3
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Most trike kits use live (spinning) axles, which means that the hubs must attach directly to them rather than have bearings. Otherwise the axle would spin in the hub and you wouldn't go anywhere.

Typically the drive is at the center where there is usually an open cross-brace where one or both axles come in and the drive sprocket is mounted. A common arrangement is to use a dummy hub so that standard cassettes and RDs can be used, then a short loop of chain to the axle sprocket. The long trike axle spins on bearings within the adapter and the wheel hubs mount on outer ends.

Visit this site for an idea of how they look.
THANKS!

This is exactly how I imagined it, when I drafted the second arrangement.

What are viable options for a mechanical attachment point, on the frame, for such a conversion kit? dropouts, or somewhat higher on the seatstays? Or dropouts and seat tube (near the top)?
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Old 05-05-10, 06:32 AM   #4
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Before you spend a lot of time (and money) building a trike, I would try to find one to borrow or rent for a couple of days.

They ride much differently than a bike (in my opinion, they are horrendous to ride).

Just suggesting that if you haven't ridden one any distance, you might want to give it a whirl to make sure you don't hate it...!

edit to add: I have achieved great safety in winter with studded tires, and unbelievable cargo capacity with xtracycle. I never use my cargo trailer anymore.
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Old 05-05-10, 06:44 AM   #5
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Usually you'd attach to the dropouts, with a secondary brace to the seatstays or chainstays for rigidity.
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Old 05-05-10, 06:46 AM   #6
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Usually you'd attach to the dropouts, with a secondary brace to the seatstays or chainstays for rigidity.
Isn't it a bit risky to use the chainstays for this purpose, from a structural safety POV?
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Old 05-05-10, 06:49 AM   #7
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I know you mean well, but don't you think that
- I have already used studded tires (a lot, in fact) and have therefore some educated reasons why I chose to have a trike?
- I wouldn't be willing to pay $1200 + $BIG****INGNUMBER for shipping, for an xtracycle?

I knew a few comments like this are unavoidable, but I didn't want to just completely ignore your input. I think that would be impolite.

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Originally Posted by larry_llama View Post
Before you spend a lot of time (and money) building a trike, I would try to find one to borrow or rent for a couple of days.

They ride much differently than a bike (in my opinion, they are horrendous to ride).

Just suggesting that if you haven't ridden one any distance, you might want to give it a whirl to make sure you don't hate it...!

edit to add: I have achieved great safety in winter with studded tires, and unbelievable cargo capacity with xtracycle. I never use my cargo trailer anymore.

Last edited by wroomwroomoops; 05-05-10 at 05:24 PM.
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Old 05-05-10, 07:23 AM   #8
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I know you said you didn't want a kit, but if for some reason you change your mind then here's one for $229 you can check out.
http://www.bicycledesigner.com/defau...umber%3D870000

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Old 05-05-10, 07:38 AM   #9
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That kit is a terrible deal! It doesn't even include the wheels. And their shipping service sucks monkeyballs: "Order Total $447.05" I guess you've not been paying attention.

If I really did want a kit, I'd order the one FBinNY linked to, which includes wheels AND costs $200. But considering postage, custom and taxes, even that is too much.


Is it possible to keep this discussion technical?

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I know you said you didn't want a kit, but if for some reason you change your mind then here's one for $229 you can check out.
http://www.bicycledesigner.com/defau...umber%3D870000

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Old 05-05-10, 08:05 AM   #10
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Isn't it a bit risky to use the chainstays for this purpose, from a structural safety POV?
It's one of those trade offs you and have to do some stress calculations. There are two issues.
1- torque, wherein the entire rear end is cantilevered out beyond the dropouts and would tend to rotate upwards.
2- twisting forces as either rear wheel hits a bump and rocks the unit (and frame) sideways.

For the twisting higher bracing to the seatstays or upper seat tube would be preferable, but for simply supporting the unit, reaction arms extending below the chainstays and tied off there would probably serve very well. The chainstays have the advantage of being stiffer and shorter so they'd offer more rigidity than going a few inches the long and slender seat stays.

BTW- you might not need bracing to control the twisting forces if the dropouts are beefy enough, unless you expect to be using in on very rough roads, I've also seen some make a rear basket something of a structural element to add rigidity to the entire unit.

Lastly there's the question of a differential, and braking. You have to think about this a bit. Some units only drive one wheel, eliminating the need for a differential, but that means there's be some torque steer especially when the (inboard) brakes are applied. If you drive both wheels without a differential there'll be some scuffing on turns (I don't know how much this matters).

I knew of one racing trike years ago that drove both wheels with a common axle but each hub had a freewhel so the outer wheel could overrun the inner on turns, and used rim brakes to stop.
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Old 05-05-10, 08:24 AM   #11
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I was worried mostly about the torque (axis parallel to the rear wheel axis), and didn't think much about twisting. I somehow implied that fixing the former would take care of the latter as well. If I ran two rods from the rear wheel construct towards the upper part of the seat tube, I'd form a sort of triangle, somewhat reminiscent of the structure you have on mixte frames. Not the lightest, but I thought, simple and rigid.

I definitely did not think about the differential. Or better say, I did, and implied that it wouldn't be much of a problem. From what I can see, the commercial conversion kits don't take care of this problem, either. I do like the idea of two separate freewheels, but that would make the drivetrain quite complicated. I guess? It probably could be done this way, on the cheap: get two used steel (front) forks. Respace them so that a 120 mm rear hub could fit. This might be a bit of a challenge, but not impossible. Have a long axle with a fixed gear in the middle, driven by a gear on the rear hub, which sits in the rear dropouts. This last thing needs a bit of engineering on the rear hub body. The long axle would also have two cogs near each end, drive the freewheels on the hubs in the forks. These forks would be welded onto a rear basket of some sorts, forming a single unit. Added bonus: one could use 700C wheels with the basket having it's baricenter well below the hub of the wheels.


but I'm really curious, how much does having a differential count, in practical terms? Do purpose-built tricycles have differentials, usually?

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It's one of those trade offs you and have to do some stress calculations. There are two issues.
1- torque, wherein the entire rear end is cantilevered out beyond the dropouts and would tend to rotate upwards.
2- twisting forces as either rear wheel hits a bump and rocks the unit (and frame) sideways.

For the twisting higher bracing to the seatstays or upper seat tube would be preferable, but for simply supporting the unit, reaction arms extending below the chainstays and tied off there would probably serve very well. The chainstays have the advantage of being stiffer and shorter so they'd offer more rigidity than going a few inches the long and slender seat stays.

BTW- you might not need bracing to control the twisting forces if the dropouts are beefy enough, unless you expect to be using in on very rough roads, I've also seen some make a rear basket something of a structural element to add rigidity to the entire unit.

Lastly there's the question of a differential, and braking. You have to think about this a bit. Some units only drive one wheel, eliminating the need for a differential, but that means there's be some torque steer especially when the (inboard) brakes are applied. If you drive both wheels without a differential there'll be some scuffing on turns (I don't know how much this matters).

I knew of one racing trike years ago that drove both wheels with a common axle but each hub had a freewhel so the outer wheel could overrun the inner on turns, and used rim brakes to stop.
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Old 05-05-10, 08:48 AM   #12
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I don't think the differential is critical. I've seen single side drive/brake and am not a fan and I've seen solid axle systems and the scuffing seems not to matter enough. The racing version was the only one I'd ever seen and it was purpose built and I think the reason was to reduce power loss as much as possible and improve control. However most folks racing trikes pick them up onto the inner wheels for high speed cornering anyway.

In your case, I'd go solid axle all the way across. I'd also extend a reaction arm under the chainstays (like a coaster brake arm), then triangulate the outer ends up to the seat lug or high on the seatstays for rigidity. Since it's to be a work trike you might tie the axle ends and upper frame together via the basket unit.

BTW- if you google tricycles creatively like "adult tricycle" or other qualifiers, you should get some pictures of what others have done and pick up some hints. Your main challenge will lie in buiding the "banjo" axle housing and bearings, providing good structure and decent bearings, and connecting the single axle with the central drive sprocket.

I can see why you'd rather do your own, but like I said learn as much as you can from what's already out there.
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Old 05-05-10, 09:07 AM   #13
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This is excellent information (I mean, all the good info you provided in the whole thread). Thank you very much.

How would the reaction arm be mechanically connected if I don't want to run a roller, drum or coaster brake for now? I mean, to which component would it be affixed, other than the chainstay?

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I don't think the differential is critical. I've seen single side drive/brake and am not a fan and I've seen solid axle systems and the scuffing seems not to matter enough. The racing version was the only one I'd ever seen and it was purpose built and I think the reason was to reduce power loss as much as possible and improve control. However most folks racing trikes pick them up onto the inner wheels for high speed cornering anyway.

In your case, I'd go solid axle all the way across. I'd also extend a reaction arm under the chainstays (like a coaster brake arm), then triangulate the outer ends up to the seat lug or high on the seatstays for rigidity. Since it's to be a work trike you might tie the axle ends and upper frame together via the basket unit.

BTW- if you google tricycles creatively like "adult tricycle" or other qualifiers, you should get some pictures of what others have done and pick up some hints. Your main challenge will lie in buiding the "banjo" axle housing and bearings, providing good structure and decent bearings, and connecting the single axle with the central drive sprocket.

I can see why you'd rather do your own, but like I said learn as much as you can from what's already out there.
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Old 05-05-10, 01:16 PM   #14
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I definitely did not think about the differential. Or better say, I did, and implied that it wouldn't be much of a problem.....but I'm really curious, how much does having a differential count, in practical terms? Do purpose-built tricycles have differentials, usually?
Apart from perhaps tadpole trikes, most people riding trikes do so because it's the only riding left available to them. Means that there aren't many people asking for "performance" trikes.
Schwinn has a factory trike, which hasn't got a diff. Consensus from another forum was that people who had a solid bicycling background reacted to it handling differently in L/R turns, while non-riders who were looking for an alternative to walking(due to restricted sense of balance for instance) were quite content.
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Old 05-05-10, 01:43 PM   #15
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That's really good to know. I do have quite a lot of cycling experience, but if all I will notice is that I'll "react to it", well I'm really fine with that. As I said, I want to haul groceries and have a solid ride for the winter. The last winter in Finland was exceptionally snowy, and I was seriously contemplating getting a Surly Pugsley, but I am far from able to afford it, now that we have a little baby boy at home.

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Apart from perhaps tadpole trikes, most people riding trikes do so because it's the only riding left available to them. Means that there aren't many people asking for "performance" trikes.
Schwinn has a factory trike, which hasn't got a diff. Consensus from another forum was that people who had a solid bicycling background reacted to it handling differently in L/R turns, while non-riders who were looking for an alternative to walking(due to restricted sense of balance for instance) were quite content.
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Old 05-05-10, 01:47 PM   #16
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If the two rear wheels will both be driven then a differential is essential. There would be a HUGE amount of friction and lost effort by the two contact patches fighting each other on a locked axle. I could easily see it being bad enough that you'd have trouble steering effectively. On a car or truck with lots of power such friction isn't a big deal. On a trike with a single manpower for energy it would be a big factor. This is likely the big reason why the low rider tadpole and delta style trikes all have only one driving wheel.

On a bicycle to trike conversion if you leave the axle line at the classic position of the dropouts your rear wheels will be a LONG way back. Combine this with a rather high center of gravity and you'll find that a bike to trike conversion of this sort will be extremley tippy unless the wheels are spaced out a lot. A better conversion would shift the rear axle axis forward as much as possible so that the overall center of graivity is positioned closer to the dual wheel axle. Both of the kits linked earlier and many of the commercially available upright trikes fail miserably on these factors. I'd much rather just ride with studded tires in icy conditions than with either of these conversions. In particular the second conversion kit which moves the axle line back by a good 5 or 6 inches and compounds the issue.

I know that this example is not a conversion but it's an example of what I mean about the rear axle position with respect to the rider's mass and the need to move that mass further back between the rear wheels to achieve proper stability. It's sadly also the only one I could find that seems to locate the dual wheel axle closer to the rider's center of mass. All the others resemble the kit conversions more closely and for anything other than very slow and casual riding would be extremely tippy. It would appear that the lowrider delta and tadpole trike folks are the only ones that take trike stability and performance seriously.

http://video.google.com/videoplay?do...14500244331571#
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Old 05-05-10, 02:00 PM   #17
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There is some good reading on trikes on this guys bike blog: http://pedal-trikes.blogspot.com/
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Old 05-05-10, 03:45 PM   #18
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Hey Woomwroomoops,

I was paying attention. You said you didn't want a kit...first thing I said. I just thought I'd be nice posting that sight just incase you changed your mind, wanted to check them out, they carry trike parts, etc. You said you could probably get used 26" wheels. That kit doesn't come with wheels, so less shipping, which you were crying about, right?

Sorry I wasted your time!!!
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Old 05-05-10, 03:55 PM   #19
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Mr. Gnome: I specifically mentioned that I'm not buying trike conversion kits. If you're associated with bicycledesigner.com, tell them (or yourself) to lower those ridiculous shipping expenses. And don't use the 26" wheelsize as an excuse for your astroturfing. Thanks and bye - I'm putting you on iggy.
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Old 05-05-10, 04:04 PM   #20
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For someone with 4386 posts one would think that you would have learned to be a little more polite on forums.

Yes he did post a link to a kit. But when you're looking for information on making or somehow adapting stuff any information can be useful.

You'll likely think that I also wasted your time. I welcome you to go ahead and put me on your ignore list as well. At least I'll enjoy the company more.
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Old 05-05-10, 04:08 PM   #21
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You raise a good point about the trippiness of this structure - provided that you're talking about sideways trippiness. I'll definitely put that into the mumble mumble. The center of gravity isn't, however, particularly high - about the same as with a regular bicycle. In fact, even a bit lower when loaded.

Differential: FBinNY and dabac convinced me that it's not essential. Now you are trying to convince me that it is. I don't necessarily believe that "the truth lies somewhere in the middle", so which one is it? If Schwinn and many others have been making trikes without a differential, could it be that it's not, actually, indispensible? I get that you'd lose some energy during cornering, but maybe that's not such a big issue if you're not in a hurry and can shift low enough gears to generate the necessary torque?

I do have plenty of studded tires (a couple of both Schwalbe Ice Spiker, Nokian Extreme 294 and Nokian Hakkapelitta W240. Previous ot these I used the Hakkapelitta 106 and Schwalbe Snow Studs, but they had way too few studs to offer a reliable traction in all condition. Turns out, with loose snow (when themperatures are very low and cars turn snow into some sort of loose sand) or with half-melted snow, especially when there's a mountain of it, no studded tire will help. As I said, I considered the Surly Pugsley with the Large Marge rims and the Endomorph (I think) tires. But that setup is extremely expensive.


In other words: this trike is gonna happen.

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If the two rear wheels will both be driven then a differential is essential. There would be a HUGE amount of friction and lost effort by the two contact patches fighting each other on a locked axle. I could easily see it being bad enough that you'd have trouble steering effectively. On a car or truck with lots of power such friction isn't a big deal. On a trike with a single manpower for energy it would be a big factor. This is likely the big reason why the low rider tadpole and delta style trikes all have only one driving wheel.

On a bicycle to trike conversion if you leave the axle line at the classic position of the dropouts your rear wheels will be a LONG way back. Combine this with a rather high center of gravity and you'll find that a bike to trike conversion of this sort will be extremley tippy unless the wheels are spaced out a lot. A better conversion would shift the rear axle axis forward as much as possible so that the overall center of graivity is positioned closer to the dual wheel axle. Both of the kits linked earlier and many of the commercially available upright trikes fail miserably on these factors. I'd much rather just ride with studded tires in icy conditions than with either of these conversions. In particular the second conversion kit which moves the axle line back by a good 5 or 6 inches and compounds the issue.

I know that this example is not a conversion but it's an example of what I mean about the rear axle position with respect to the rider's mass and the need to move that mass further back between the rear wheels to achieve proper stability. It's sadly also the only one I could find that seems to locate the dual wheel axle closer to the rider's center of mass. All the others resemble the kit conversions more closely and for anything other than very slow and casual riding would be extremely tippy. It would appear that the lowrider delta and tadpole trike folks are the only ones that take trike stability and performance seriously.

http://video.google.com/videoplay?do...14500244331571#
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Old 05-05-10, 04:20 PM   #22
wroomwroomoops
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I don't need to read the posts of a company's shill. I was plenty polite for not putting him/her on ignore after his/her first post. First in this thread and first ever on bikeforums.net.


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Originally Posted by BCRider View Post
For someone with 4386 posts one would think that you would have learned to be a little more polite on forums.

Yes he did post a link to a kit. But when you're looking for information on making or somehow adapting stuff any information can be useful.

You'll likely think that I also wasted your time. I welcome you to go ahead and put me on your ignore list as well. At least I'll enjoy the company more.
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Old 05-05-10, 04:41 PM   #23
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BCRider,

Thanks for the support. Whatever I did in that reply, and for that matter, the first one here...shoot!!! I knew he didn't want a kit (I think that was the first words I said), but sometimes you have to change your mind to get things to work...or decide maybe that would be a better way to go, etc. Just checking out the picks there maybe he could have a local shop make something up for him within his budget.

And no, I'm not with, bought from, sold to, married into, or in any way with Bicycledesigner. Most all of the stuff there is for the kids low riders, not a 56 year old retired Teamster. I just ran accross it one night searching for ideas/parts for my Sun X3-SX trike...like less teeth axle gear, larger wheels, etc.

Anyway, I'm outta here before I get yelled at,
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Old 05-05-10, 04:55 PM   #24
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Hey Woorm dude,

Click on my name. I joined in March and this is the first thread I replied to, so I guess I'm a pretty poor shill!!! LOL

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Old 05-05-10, 05:01 PM   #25
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Wroomwroomoops,

One issue you will have with a trike is the single drive wheel, unless you arte going to set up a positraction system. My wif'e trike absolutely sucks in snow, although it's nice on ice. Her drive wheel just spins, even using a studded tire. We've even tried rigging a kind of tire chain on the drive wheel and it did help, at least. I'll be interested in the results you get and feel free to PM me the results of your build and how it does on snow and ice.
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