Author Topic: Rohloff on a Trike  (Read 344 times)

one arm bandit

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Rohloff on a Trike
« on: July 16, 2017, 02:26:49 PM »
In addition to my Nomad Iíve now got a rohloff equipped trike with 20 inch wheels plus 2 inch tyres. This is great fun until you get to a hill. Trikes are heavy and even in gear one climbing hills is a chore and thatís unloaded.  Iím not concerned at going fast.

Currently it has 50t on the chainring and 17t on the hub. I also have a 15t in the toolbox. To complicated the matter it has a 130mm BCD so limiting the chainring choice to 38t at the smallest. Iíve worked out that the 38 / 17 combo would give me about 12 gear inches. Iíd like lower if possible.

I know little about gears and not much about bikes - I just ride the things, but I see my options as:
Stick with the 38 / 17 combo. tbh Iíll try this first.
Change the crankset entirely to get a 32 / 17 combo to achieve around 10gi
Buy a Schlumpf Mountain Drive (or Patterson drive) to get even lower. This is the expensive route. I know that rohloff frown on this but the feeling amongst trike riders is that since youíre sat down the force you can exert is much less than a 200lb athlete standing on the pedals so using a Schlumpf is ok.

One thing you don't have worry about is balance at low speeds.

So, any advice?

mickeg

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Re: Rohloff on a Trike
« Reply #1 on: July 16, 2017, 05:02:43 PM »
A 110mm BCD crank would allow fitting a 34T chainring.  I do not know what your bottom bracket is, the crank I am citing fits on a square taper.  A triple crank that also has a 74mm BCD chainring could go lower than you would ever want to go.

I think I only paid about $35 USD for the crank on my Nomad, a Vuelta 110mm double crank for square taper.  Bought it on Amazon.

I had a very long hill climb several years ago on my Sherpa, Going to the Sun Road in the American Rocky Mountains.  One guy in our group had a trike.  He kept plodding up the hill really slow while the rest of us occasionally had to stop to take a break because we had to pedal hard enough to go fast enough to stay vertical, he could go as slow as he wanted.


Danneaux

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Re: Rohloff on a Trike
« Reply #2 on: July 16, 2017, 05:20:20 PM »
Like you -- and given the constraints of your crankset -- I'd try the 38x17 combo first.

Back in the days when I made my own extra-low derailleur gearing by using chainrings as cogs and cogs as chainrings with modified derailleur cages (and links in the case of quad-chaining setups), I got as low as 12.5 gear-inches. This was the practical minimum for me wrt maintaining balance, which is not a consideration for you with the trike.

What I did learn that might apply to your situation is this: It seems the human body perceives changes in gears logarithmically. By that,  I mean larger jumps between gears at the low end are needed to "feel" like smaller jumps between higher gears. For this reason, I used to plot my gears on log paper to better visualize the jumps between and so have some idea how they would feel before I built them up (this was in the days before personal computers. I switched to homebrew gear calculators I wrote for mainframes as soon as I could gain access to one...).

The upshot of this is if you go for the 38x17 combo for a low of 12 gear-inches and find it isn't enough, then you will likely indeed have to take more drastic measures and fit something that allows you to go substantially lower for it to *feel* lower. Options at that point might include a different crankset that allows smaller chainrings than your present 130BCD (second-cheapest option to keeping what you have) or going the much more expensive route of a (in order of cost) Patterson drive, Hammerschmidt, or Schlumpf 2-sp internally geared *underdrive* crank/bottom bracket.

I recently served as a purchasing agent for a Bavarian friend who wanted a Patterson drive, so I had the chance to examine it closely and dry fit it. Compared to the Schlumpf drive, the Patterson does not require you to bevel/camfer the BB shell. It uses a standaRd front cable shifter of any sort, but is not as well sealed a the Schlumpf or Hammerschmidt -- a real consideration for use on mid with a conventional upright bike, but not so much with the elevated boom of a recumbent, which I presume you have. The torque reaction tabs work nicely with a conventional BB/chainsaw setup, but would need to be adapted to a recumbent boom

There are some low-gearing cautions I can offer well beyond Roloff's and they are very real, based on my own practical experience. Super-low gearing results in tremendous torque-induced loads on the drivetrain. For example, I found my freewheels would twist onto the hubs so tightly the hub shoulders would distort. To solve this problem, I made my own crushable aluminum thrust washers until I found a source for aluminum BB spacers, which are the same diameter as freewheel threads. These, along with molybdenum disulfide paste grease kept the hub shoulders intact and allowed me to remove the freewheels. Even so, I found continued use even in a well built wheel would pull the right side hub flange slightly ahead of the left due to torque through a then-standard small diameter hub center, worse with large flange hubs.

The next weak link in the chain is the chain -- super-low gearing makes it much easier for even a weaker rider to pull one apart in other than straight-chain gear combinations. Aluminum chairing teeth can distort, so steel becomes a better choice. If you have ramped dropouts, it is much harder to hold the wheel in place with a standard quick-release;  a solid axle with nuts and serrated washer is a better choice. I found vertical dropouts were no real help, as at a certain point, the axle was pulled forward with so much force, the axle threads would emboss and slightly distort even a forged vertical dropout on the drive side if the axle became even a little loose 

If you are hauling a lot of weight, if the hills are really steep, if you are a masher or a very strong rider, all thse forces are increased, usually beyond design limits.

Wear increases dramatically, partly due to the increased torque and partly due to smaller pinion diameters and increased rotations.

Mine were worst-case examples: 50kg all up bike/cargo loads + my weight on an upright bike going up >20% grades at 12.5 gear-inches. Though I have always been a spinner, at the time I was riding 19,000+km/year and a friend doing his doctorate in kinesiology measured me on his ergometer, where I could ever so briefly generate 0.32 peak horsepower.

Just some data points to consider, but I think you may well run into Roloff Trubbles if you go too low and add those other risk factors The key with the Roloff's limitations is not so much pure gear-inches as it is ratios. Before going to a 2-speed underdrive crankset, I would swap for a different conventional  crankset that allowed smaller chainrings.

Hopefully helpful.

Best,

Dan.
« Last Edit: July 16, 2017, 05:27:43 PM by Danneaux »

one arm bandit

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Re: Rohloff on a Trike
« Reply #3 on: July 16, 2017, 09:13:24 PM »
Thanks guys.
Since most trikes are derailleur there 'should' be no problem with fitting a regular crankset with whatever is the best ring.

If the 38/17 isn't low enough at 12gi then the lowest recommended combo is 30/16 which produces about 10gi. Will I notice the benefit for the expense and hassle?     
The Patterson drive sounds like it would be best but as usual its money.

I think, Dan, you're right. Putting a conventional double ring crankset of, say, 44 and 28t with a front shifter just might work. The chainline isn't that critical as the length of the chain must be well over a meter (much of it through tubes) and I have a chain tensioner on the rohloff to take up the slack. I have no idea if this just can't / won't work so shoot me down.                 
As for damaging the components, I very very much doubt that I'll be able to do that. I'm not strong enough and I'll be sat down.

energyman

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Re: Rohloff on a Trike
« Reply #4 on: July 16, 2017, 09:56:32 PM »
Any chance of a photo please ?
(I have a trike in my shed waiting for a refurb)

one arm bandit

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Re: Rohloff on a Trike
« Reply #5 on: July 16, 2017, 10:13:21 PM »
What of? The whole trike, the front chainring??
Its an Ice Sprint 20
http://www.icetrikes.co/products/sprint-recumbent-trike
3x 20inch wheels. Front chainwheel is a single as you would imaging, looong chain to the rohloff
Fantastic fun downhill and pretty quick on the flat but very slow uphill. Someone said to me 'just spin up and take a sandwich to eat'

energyman

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Re: Rohloff on a Trike
« Reply #6 on: July 16, 2017, 10:34:03 PM »
Thanks

martinf

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Re: Rohloff on a Trike
« Reply #7 on: July 16, 2017, 10:58:35 PM »
Another possibility - get a sprocket with more teeth and keep the chainset and use a 38T chainring.

In screw-on Rohloff sprockets, the biggest I know about is 19T (which I have on my Raven Sport Tour with a 50T chainring).

In the new splined Rohloff sprockets the biggest I know about is 21T.

Depending on the actual size of the tyre, 38x21 on a 20" wheel will give a low gear of about 10", and a highest gear of about 53", which is too low, even for me, this equates to about 23 kph at 90 rpm.

If you keep your 50T and run a 38/50 double chainring with a 21T sprocket you could get gears from about 10" to 70"

For a cycle with very wide range gearing I reckon 70" highest gear is still a bit low. For a loaded trike I'd consider 38/50 double chainring with a 19T sprocket a better compromise. With nominal 20" tyre size, this would give a gear range from about 11" to 77" and still be in the range covered by the Rohloff warranty. If the 77" top gear isn't enough you could go to a 38/54, this would increase top gear to about 83" and the derailleur should still shift reasonably well with a 16T difference between chainrings.

My utility bike has an 8-speed Nexus hub, 38x22 which gives a range from 23" to 71".  Top gear equates to about 31 kph at 90 rpm. For very short periods in favourable conditions (downhill, strong tail wind) I can push it to 42 kph at 120 rpm, so top gear is high enough for my purposes on that bike. Lowest gear equates to about 10 kph at 90 rpm. If necessary I can pedal slower, minimum comfortable for me on that bike is about 7 kph at 60 rpm. This gear range is adequate for trailer towing (probably equivalent to a loaded trike) on the moderately hilly routes around my home, but I'd want much lower gears if towing a fully laden trailer on mountain routes.     


mickeg

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Re: Rohloff on a Trike
« Reply #8 on: July 17, 2017, 12:09:34 AM »
I saw a trike like that last summer in Iceland, he had a Rohloff on it.  Photo attached, although from the photo you can't see the Rohloff.

I mentioned that in the group I was in for a trip in the American Rockies several years ago, someone had a trike.  That looked like the one you have too.  He pulled a two wheel trailer with his gear, thus five wheels on the ground.  But only one of five wheels was a driving wheel, thus he was concerned about any steep hills on gravel, as he might spin with too much torque.

From behind at a distance that trike was not very visible from a drivers perspective.  I hope you use a flag pole.





one arm bandit

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Re: Rohloff on a Trike
« Reply #9 on: July 17, 2017, 09:46:54 AM »
Martinf. Are you saying that a derailleur would work, assuming I can physically fit one? The 21T sprocket sounds ideal assuming I can fit a double. I'd prefer something like a 32/48 to get the low gear below 10gi.

Mickeg. I plan to put panniers over the rear wheel with enough weight to anchor it and tow a trailer with lighter, more bulky, stuff
I thought the same as you about being visible but surprisingly that's not the reality. For a start I have 3 hi intensity rear lights and 2 front all flashing plus a flag. Mainly I use only the front 2 & 1 rear. I've always been an advocate of a rear flashing light esp in low light and intermittent shade. I have a good mirror on each side.
Cars are extraordinary careful of overtaking me. They don't quite understand what I am or whether I'm disabled (think hand powered trikes) so they slow down and most go right over the other side of the road. Most have their wheels at the opposite curb even on a fast road. I've watched the same car overtake my wife 100m ahead and they leave the usual 1m. It's such a pronounced difference that my wife now mainly stays within that protective 'bubble'.
The only time I think it works against me is if I'm turning right (in the UK), someone behind me slows down but someone behind them can't see me, overtakes them and hits me as I turn into their path. This can happen on a bike, of course but is a bit less likely. The other issue is passing parked cars with someone pulling out of a driveway having not seen you. Being doored is not so serious imo as there's a lot of trike and legs before you hit with your head and you're less likely to launch off into oncoming traffic I would think. Since I mainly cycle with my wife on an upwrong :) she acts to protect me as I do her.
I can see that meeting farm tractor on a narrow road where with a bike you just hop off and get over isn't going to work. In that case, I just hop off drag the trike around and go back to a wider part.
Turning circle is poor and no reverse gear.
Clipless pedals are very much needed as the prospect of a foot bouncing off a pedal and getting dragged underneath at 20mph is unappealing.
So yes there's problems and bikes are more agile. Personally speaking I have serious balance issues due to a historical head injury and fall off my Nomad a lot. Last time I broke some fingers. For me trikes are the answer - no falling! The rohloff was originally chosen because of the usual reasons compounded by a loss of timing and dexterity. But hey, I can ride a bike which is, according to my neuro's, almost unheard of at the time I relearnt to ride.
But overall, bikes are better.

one arm bandit

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Re: Rohloff on a Trike
« Reply #10 on: July 17, 2017, 09:50:16 AM »
Mickeg

Was the trike in Iceland on a gravel interior road? I'd like to visit Iceland but crossing the interior is a must.

martinf

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Re: Rohloff on a Trike
« Reply #11 on: July 17, 2017, 02:14:53 PM »
Martinf. Are you saying that a derailleur would work, assuming I can physically fit one? The 21T sprocket sounds ideal assuming I can fit a double. I'd prefer something like a 32/48 to get the low gear below 10gi.

I've run a double chainring with front derailleur and single rear sprocket on a hub gear without problems.

In my case an old Sturmey-Archer 5-speed, not a Rohloff, but the principle is the same.

I did this on a Brompton folding bike, to get a wider gear range for touring in hilly areas. The Brompton has a chain tensioner that will cope with at least a 20T gap in front chainrings. The racing-type front derailleur I adapted on the Brompton coped well with a 16T chainring gap, so that is what I used. I experimented with a bigger chainring gap and a "touring" type front derailleur,  20T was possible, but the change was not so smooth.

There are at least 4 variables to watch out for :

- chainline. I managed to get this so that the rear sprocket was aligned with the gap between the two chainrings. This will probably not be an issue with a trike.

- gap between chainrings. I like to keep this to 16T on a double, but more is possible with a suitable front derailleur. I believe a triple shifts better than a very wide range double, my one remaining derailleur bike has 28/46/50, this shifts without problems using an old Dura-Ace racing style front derailleur.

- capacity of the rear derailleur or tensioner. This must be adequate to take up the chain released, and depends on chainring gap. It shouldn't be a problem, as you don't have to worry about multiple rear sprockets, but with small wheels you also need to consider ground clearance, within the limits of possible avoid having a tensioner/rear derailleur that hangs too low, apart from the risk of damage, the lower it hangs, the more road dirt it picks up.

- clearance. You have to make sure that the chainrings, rear tensioner, rear sprocket, etc. are compatible with the frame.

Your proposed 32/48 should shift easily. Top gear seems a little low to me, and 32x21 will invalidate the Rohloff warranty (ratio 1.52, AFAIK the lowest ratio permitted by Rohloff is 1.9).

I have ignored the recommended ratio on my wife's bike, this has a 30x19 combination, so an input ratio of 1.57. This bike runs a Shimano Nexus Premium 8 hub, which is a fraction of the price of a Rohloff, so I don't worry about warranty issues.
« Last Edit: July 17, 2017, 02:53:07 PM by martinf »

mickeg

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Re: Rohloff on a Trike
« Reply #12 on: July 17, 2017, 08:00:21 PM »
Mickeg

Was the trike in Iceland on a gravel interior road? I'd like to visit Iceland but crossing the interior is a must.

That photo of the trike was down in the lower areas where the roads were paved.  That was the only trike I saw in Iceland.

Interior, the gravel roads, some are almost like pavement (tarmac) but some are pretty bad with cobbles.  Also, since there is little traffic in the interior, although the roads are generally wide enough for two vehicles, people are mostly driving down the middle.  Thus, the roads might not be that friendly for a trike that has three wheel tracks. 

Down in the lower areas, the roads although paved have minimal shoulder at the sides.  And the few times that have more shoulder they have the rumble strips (not sure if that is what they are called in the UK) which would be more problematic if you have three wheel tracks instead of one.

You can see photos of some of the interior roads at this post I created about my Iceland trip.
http://thorncyclesforum.co.uk/index.php?topic=11917.0

I pushed my bike up several hills in the interior, some of that was because of cobbley roads, if I spun out I could not start on too steep a hill again so had to push the rest of the way.  And part of it was just being tired and pushing allowed me to go slower.  In the interior, quite often I would be part way up a tall hill and a tour bus would come along, forcing me to get to teh side of the road where I could not maintain headway.  Thus, I often had to push the bike up the rest of the hill because of those <insert swear words here> tour buses.

My first two days in the interior I used SPD cleated shoes.  But after that I switched to hiking shoes.  I used Shimano M324 pedals, I can use either on those pedals.  The hiking shoes were much preferred on the cobbles for pushing up hills.  I like to be able to get my feet on the ground really fast when I am on difficult gravel and cobbles in the event that something goes wrong, being cleated in is something that I try to avoid in slow difficult terrain.  Thus the hiking shoes were also preferred for pedaling in the interior.

I attached three photos here, first two shows the lack of shoulder that is common on secondary roads in Iceland.  Third photo is a main road approaching Reykjavik, there is a rumble strip at the left side of the shoulder that would be problematic with three tire tracks.

I added a fourth photo, just because I like it.

one arm bandit

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Re: Rohloff on a Trike
« Reply #13 on: July 18, 2017, 12:22:55 AM »
Thanks Mickeg. UK roads mainly have no shoulder & bike paths are few in number. Basically you're cycling with cars around you.

Tigerbiten

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Re: Rohloff on a Trike
« Reply #14 on: August 18, 2017, 01:40:43 PM »
I have a Rohloff and a Schlumpf HSD on my ICE Sprint trike for the last 6 years.
My gearing now is a 54/38 double up front and a 21 tooth sprocket, 9.5"-175".

I started 30/16, but the shift into the overdrive was at too low a speed, around 14 mph.
I then tried 30/13, this was better as the shift was around 20 mph but I'd lost the ultra low gears I wanted.
Thats when I worked out with a 21 sprocket I could run a 54/38 double on the HSD, as the minimum spider size on the HSD is 130 BCD.
It is just out of spec but it works and I don't think going for lower gear is worth it unless you have very weak legs.
This combo works fine, low range to 14 mph, high range to 20 mph, low overdrive to 35 mph and high overdrive to 50 mph ......  ;D
I prefer the HSD to the mountain drive as the extra drag is in the high range and now I use twin chainrings I don't use overdrive that much unless I'm going silly speeds downhill.
The only downside I can think of is the spider is only held in place by a circlip.
If you shift chainrings under load then you can pop the circlip if you get it wrong, but you soon learn to treat it as another hub gear and shift the chainrings under no-load. It's been a couple of years since I last pop it.

I've been around Iceland on my trike and I wouldn't like to do the gravel roads unless I was on a fat trike, the extra drag from the tyres digging to the soft surface is a killer.
« Last Edit: August 18, 2017, 01:47:11 PM by Tigerbiten »