newbert

Just got a brand new HP Velotechnic Scorpion FS 26 with the intent to replace my Catrike Villager. It's only been 2 days so far but I'm frankly shocked at how much more pedalling effort this HP requires than my Villager! I figure there's got to be something wrong, so I hope to get some ideas to check here.

First, the Specs between the two:

Catrike Villager:
3 20" wheels
Bosch "eCat" 250w eAssist Motor
Standard gearing and derailleur on back:
Standard disc brakes
No parking brake on rear tire

HP Velo Scorpion FS 26:
2 20" wheels and 1 26" wheel
Shimano Steps 250W EP8 w/640W battery
Bosch Rohloff Internal Hub on rear wheel
Standard disc brakes
HS Mesh Seat so slightly higher seating position from Catrike
Hydraulic Parking Brake on rear wheel
Significantly heavier than Villager

Now here's my problem - on the same road, on the same day, I can ride my Villager at the same speed or faster in ECO mode as the Scorpion in BOOST mode - and with significantly less effort! The Shimano on the Scorpion supposedly has almost twice the torque in neuton-meters as the Bosch on the Villager (90 vs 50 AFAIK). I can only think of 5 possible reasons why the Scorpion takes so much more effort to ride:

1. The extra weight - but shouldn't the extra power (torque) in the Shimano motor negate this?
2. The higher seat on the Scorpion changes the seat to pedal angle a bit. But would it make so much difference?
3. 26" wheel vs 20" wheel in back? Shouldn't it be faster, not slower?
4. Ive read that the Rohloff is slightly less efficient that a derailleur system (ie - more drag). But this big a difference?, and
5, Perhaps the parking brake on the Scorpion needs adjusting (ie - creating drag)?

Is this normal? Any thoughts on what is most likely at fault and what else to check (and how) would be GREATLY appreciated!

Thanks,
Bert

DeadGrandpa

Are you sure that the parking brake (if it has one; my ICE has a rim brake on the rear wheel) was disengaged? It's pretty easy to forget about it when your mind is on other things. I know someone who rode with the brake almost fully engaged
​​​​ the other day, for just over 10 miles. Thought he had a bad headwind, or something wrong with his legs.

I guess you checked that the wheels spin freely when you lift one at a time off the ground? The 26" wheel will give you a slightly higher gear range than the same sprockets on a 20" wheel. And the extra weight of the HP with the suspension and giant battery is not to be sneezed at. Without counting teeth on your cassette and chain ring and diving into Sheldon Brown's gear calculator, it's hard to say what the difference in the drive train may be.

Check the chain path and the chain tubes; make sure you don't have a chain tube binding the chain against a pulley, or vice versa. The chain could have been installed with a 180 degree twist. Rotate the chain in each direction where it comes out of a tube. It should have the same amount of play in each direction. If it resists rotating in one direction but goes easily the other way, it could have been twisted when installed.

If the front wheels were not aligned properly, that would also add rolling resistance. Good luck.

Edit: I should have said "twist" instead of "rotate" the chain. I did not mean for you to rotate the crank.

newbert

DeadGrandpa - Thanks for those suggestions.

As far as I can tell, the parking brake is fully disengaged. All wheels spin freely.

I've checked the chain path and everything looks fine there too. I don't hear any rubbing sound, but there's a slight squeak at the trike's front end as I pedal.

I don't know how to check alignment, but visually it's not completely out of whack.

I realize that the HP is significantly heavier than the Villager, but shouldn't the increased torque provided by the Shimano (85 nM vs Bosch's 50 nM on the Villager) negate that increased weight? I'm totally frustrated at this point. At the bike shop, everything felt great during the test ride - The HP rode like a Cadillac!. As soon as I got home, although it still absorbs the bumps it feels like I'm dragging a trailer behind me. I'd return to the trike shop where I bought it, but it's a 10 hour round trip drive that I would rather avoid.

I'm going to top off the air in the tires as soon as my air pump re-charges. I don't expect that to make much difference though.

I'm starting to suspect that the Shimano-s eMotor settings need adjusting. Would you know of a Shimano online forum to ask questions about using their app to make adjustments?

Thanks again!
Bert

DeadGrandpa

I feel your frustration. I know little to nothing about the relative power of the different motors. Nm per pound of trike? I know if I'm just starting a ride, with legs not warmed up, I can reach 9 mph comfortably in the first hundred yards, with the e-assist still turned OFF. I hit the button and the ECO assist level adds 2.5- 3 mph for the same leg effort. If the trike feels sluggish now, but didn't at the dealer, I wonder if a trip back to the source might be necessary, however unpleasant. Any chance the Rohloff hub is the malfunction?

I found this forum by accident; hope it helps.

https://electricbikereview.com/forum...ebike-forums.3

Leisesturm

Dead Grandpa asked excellent questions. I too suspected a parking brake scenario. Because of the 26" rear wheel the HPV is geared significantly higher than the Catrike. It's literally geared for speed. I imagine the motor software should allow you to compensate. I don't know of any online forum supporting Shimano products but maybe the manual for the Steps Drive is online. I'll take a look. Thing is, long term you don't want to use motor torque (battery life) to compensate for bad gearing. For what you paid I don't think asking for mountain gearing is out of line. Essentially, by using smaller front rings or larger back rings (or both) you get (back) the same kind of gears you had on the Catrike with the 20" drive wheel.

newbert

Thanks for your thoughts, Leisesturm.

I think that what you're saying makes sense - for a stock HP SF26. But mine has the Shimano motor at the pedals and a 14 gear Rohloff internal hub on the rear wheel. Theoretically, I chose this combo to achieve a very wide gearing range. So, based on my limited understanding, isn't any discussion of smaller or larger rings moot in this case?

Leisesturm

Well, wide is relative. As IGH goes the Rohloff is considered wide. I forget exactly but the range is over 500%. But it's 14 speeds. An 8 speed Shimano IGH has at least close to 500%. So the steps between each gear is much smaller on the Rohloff which is a good thing in general. But standard rings and cogs can offer unlimited gear range in theory. In practice ... a triple plus 10sp cassette should deliver well over 600%. But to your specific case, the Rohloff will have a drive cog that takes the input from the motor. Right now its too small. You need a bigger one. In a way its an easier fix because replacing just the one cog is going to raise the tooth count of all 14 speeds just like that.

I'm going speak in the language of gear inches. Sorry. Most bikes and trikes are set up so that the lowest gear is a 1:1 ratio or close to it. Your lowest gear is therefore equal to the diameter of your drive wheel in inches. 20" in the case of your Catrike and 26" for your new one. 6" is a huge difference at either end of the gear range. For comparison, the low gear of my cargo bike is 18". The diameter of the rear wheel is 26" but the gears are managed in such a way that it feels like it's only 18" in the lowest gear. So when you talk to your dealer they need to understand that you want a new drive cog for your Rohloff that will lower the overall gearing by at least 6". They should understand that. I forget what count is OEM on those things but the new one will be two or three teeth more in count. Not earthshattering a difference to consider intellectually but very significant where it counts. You will notice I haven't considered what will happen at the top end of the gear range. It drops 6" as well. From 116" to 110". Even if its 104" to 98" you'll be fine, I think.

DeadGrandpa

I think Leisesturm is correct. If you have ruled out impediments in the drive train, the next most likely reason for the big difference in pedaling effort is the gearing intrinsic to each of your trikes. Changing the front chain ring would be the easiest way to make the entire gearing range lower, and the pedaling easier. My trike, with a 26" rear wheel, has a 44T front chain ring and an 11-36 cassette. My trike's low gear is about 31 Gear Inches, which is not low. I just ran the numbers for the same gearing setup, but with a 20" wheel, and the low gear is about 23 Gear Inches, which approaches the low gear you might need for touring (loaded DF bike weight approximately equal to a trike with e-assist). If you change the front chain ring from 44T (or whatever you have now) to 38T, you will drop about three Gear Inches, which may not be enough. A larger cog on the Rohloff, as Leisesturm said, will also help you. If you want to, get deep into the gearing calculator. You can insert the numbers from your Catrike and the Scorpion drive train (one at a time) into this, from Sheldon Brown's website:

https://www.sheldonbrown.com/gear-calc.html

From my own experience with riding DF bikes, a low gear near 20 Gear Inches is low enough for grades up to maybe 8-10% (your mileage may vary). If you start with a low gear of 20, the Rohloff, with a 500% range from low to high, would give you a high gear near 100 Gear Inches, which is high enough for most tourists. My trike gear range is about 31 to 103. The same setup with a 20" rear wheel yields a gear range of 23 to 75. It's a compromise of gear range, weight and money. I think you made a good choice with the Rohloff, just need to tweak the driving gearing. Use the calculator to see what happens with different sizes of front and rear cog/chain rings.

FWIW, I'm looking into getting a 11-42 cassette and 38T front chain ring for mine. I'd put a 11-46 cassette on it, if the derailleur would handle it. Hope you can figure out a solution.

Leisesturm

Agreed, changing the front ring would be easier, but I'm not sure the FS26 has one. A good point made by the o.p. earlier. Some of those mid-drives only have a small cog that is physically very tiny but acts like a full size chainring due to the multiplication in the gear train. The worst ones are when they are an odd fraction of the virtual chainring.
Edit: it occurs to me that getting a larger cog for the o.p. Rohloff doesn't require a trip. The dealer can mail the part and a local LBS can make the swap. Maybe even the o.p. I don't imagine it is a difficult procedure. Probably a YouTube video tutorial on the technique.

newbert

Guys, This excellent discussion made me think of another, even more obvious solution. I'm embarrassed to say that I didn't think of this earlier or at least mention this one additional factor.

When I bought my Catrike Villager, I had some pain in my hip so my dealer installed a crank shortener (170-155?) for me. I've left it on ever since and I had it transferred over to the FS26 because I though that I needed it. Long story short - I tried the Villager today (short ride) without the crank shortener and found that perhhaps I no longer need it. So I was back at "full crank" on the Villager and what a difference that made, both in climbing and in level ground speed! So, I suspect that it would also make a significant difference on the FS26. I'll try that tomorrow,

I can't "fix" that the FS26 is heavier than the Villager, or that it has a larger rear wheel. But I can certainly make changes to the crank length (easy) and perhaps the front chain ring (if still needed).

I don't understand all your specific numbers presented but I think I "get" the gist of larger crank = easier pedalling (if all else remains constant).

That said, does anyone know the percent difference in required pedalling effort between 155 cranks and 170 cranks (all else remaining unchanged)? Just curious.

I'm learning a lot in this thread!

Leisesturm

Shorter cranks actually increase the perceived pedaling effort of a given gear. Enough so that the crank length is part of the calculation that computes the effective 'gear inch' of a front ring/rear cog combination. Usually a corresponding reduction is made in the gear ratio when short cranks are used. 155 is 91% of 170. So a (very) crude approximation is one gear higher in perceived effort. Smaller front rings and/or larger rear cogs decrease pedaling effort. Larger front rings and/or smaller rear cogs increase pedaling effort.