Author Topic: Radmission Gearing  (Read 2118 times)

mtatkow

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Radmission Gearing
« on: October 27, 2021, 06:12:57 PM »
OK - so I purchased a Radmission knowing that some things could use improvement based on the price point.  Among what I feel are shortcomings is the single speed chain line.    Where simplicity is king, and some folks get into this, the single speed is where to go.   However,  your torque input to the pedals is fairly low given the 3.125:1 stock gearing, so the result is poor battery life.   In hilly SW Wisconsin I was getting around 25-30 miles per charge down to empty.  Once you get below about 50% battery the driveline starts to struggle.

I have successfully converted the front drive using a pair (48/38) of 130BCD chainrings, proper spacers and bolts and a vintage derailleur - all from my unloved toy collection.  The derailleur was a trick, as there are limited positioning options and this one worked with only a repositioning of the controller up the tube.  An old Sun friction shifter on the left bar below the controller interface (I actually used a right one on the left mounted upside down as I like the way that shifts - backward, but easy to use) and routed the cable down the down tube along with everything else.  I added a nicer chain guard, as the stock unit is pretty drab.  The only last thing necessary was to increase the tension on the chain tensioner by 1 spring point (look at install instructions for that item and you will know what I mean) and I now have a 2 speed front end.   FYI, I doubt the stock tensioner can take up more than 10 teeth - and I might change the 38 out for a 40 as it is near it's limits with this configuration.

With the low range gear (2.375:1) I can keep the boost at a 1 or 2 and ride comfortably at 14+mph for the 1st 3 bars of the battery b4 it drops off.   Due to gearing and simply the cadence that is comfortable with the stock gearing, I used to ride at 16-17mph at boost 2-3.   Due to the improved ability to get leg torque to the wheel in low range, battery life has increased to 30-35 miles/full charge, or about 20%.  Also, generally climbing hills or pedaling with no boost (read as dead battery or broken electronics) is easier to manage (obvious).

On high range, a 4% reduction from stock to 3:1, I can tool along all day at 18mph without feeling like my legs are flailing.  (if you look at the math here, about the same cadence at 14mph low range as 18mph high range.

All changes are completely reversible.

Posting this so other Radmission owners can contemplate the benefits.   Total conversion cost, even if I had to find a new derailleur which would do the job, should be around $125-$175 depending on brand of components used.  Of the tweaks I have done thus far, this is the one that has had the most positive impact on rideability.   Keep in mind this is from a 62 year old trail rider who is putting down 18-22 miles a day on this machine every day - at least until the snow flies.

Feel free to contact me with any questions, I will try to help.

wtfg

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Re: Radmission Gearing
« Reply #1 on: October 28, 2021, 07:54:36 AM »
Show pictures!
I would like to do that too.

mtatkow

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Re: Radmission Gearing
« Reply #2 on: October 28, 2021, 02:16:24 PM »
BTW - one tech error, these are 110BCD chainrings - still easy to get hold of - I used a set of vintage Shimano Biopace rings, you can grab a complete crankset with chainrings in decent shape on Ebay for around 40-50 bucks if you shop a bit.   I've put about 50 miles on this in 2 test rides and it works well - I shift back and forth as I feel fit base on how fast I want to go and how much pedal I want to use versus motor. 


synthesizerman

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Re: Radmission Gearing
« Reply #3 on: October 29, 2021, 02:16:40 PM »
Really cool. Really interesting. Makes me wonder how gearing affects the cadence measurement.

so, if cadence is an estimate of rider effort, then having a larger front cog would cause the rad system to under estimate your effort, being on a smaller front cog would cause the rad system to over estimate your effort. is that true?

speed measurement comes from the drive wheel? It would be interesting to understand how the assist level is calculated...assist amps = alpha*(cadences/speed).


mtatkow

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Re: Radmission Gearing
« Reply #4 on: November 06, 2021, 09:46:05 AM »
The system does not really estimate "effort" like a torque system does - but that is a separate discussion.

Using 2 sprockets, the larger of which is a 48 (vs the stock 50) and the smaller being 38 gives you two fallbacks.  First, if you live near any kind of hills the 500w hub can be a bit underwhelming, so dropping back to the 38 tooth front gives you more leg power to the wheel in the form of torque.  The 48T sprocket compares very closely to the stock 50, just what I had on hand since the type of stock sprocket used is rather plain and does not behave with the shifter.

Anyway, just sharing an idea that I consider an improvement.

synthesizerman

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Re: Radmission Gearing
« Reply #5 on: November 08, 2021, 09:44:35 AM »
The system does not really estimate "effort" like a torque system does - but that is a separate discussion.

yeah, it was all hypothesis on my part. Sometimes it seems like the mission assist is just on /off. Or like you said, not really estimating effort/torque.

First, if you live near any kind of hills the 500w hub can be a bit underwhelming, so dropping back to the 38 tooth front gives you more leg power to the wheel in the form of torque. 
yeah, whenever I hit a hill, I'm slowly losing speed, even with the throttle all the way on.

Anyway, just sharing an idea that I consider an improvement.

I do think this is really interesting. I was just trying to raise question for an overall discussion, not be critical. Thanks for sharing.

mtatkow

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Re: Radmission Gearing
« Reply #6 on: February 27, 2022, 07:16:47 AM »

BTW - I recently completed the gearing change.   I installed a 3 speed freewheel - yes, Chinese replacements are still available out there in ether-land, right off Amazon - and a vintage Suntour VGT Luxe derailleur I had on hand along with the matching friction shifter from what I showed above on the left.   Just what the Dr. called for - rear cogs of 16/19/22 in combination with the front 48/38 lets me ride this much of the time like a bicycle and hit the boost when I have a bad headwind or a hill.  It also got rid of the proprietary chain tensioner used by RAD.  I can now climb most light grade hills in level 1 or 2 without too much effort - all up to the rider and their desire to get a workout vs using the throttle.   If anyone wants pictures and some guidance on how to do this, please contact me offline.  If you have sources for some parts, or have a parts bin from your bicycle hobby, this is an inexpensive and a major upgrade to the bike.  The hardest part was finding a derailleur hanger - I used one from a TREK 7100 that I was able to modify in about 20 minutes with hand tools for the job.

PS - I had to add a spacer on the hub to assure that the derailleur did not touch spokes.   My measurements say I could have installed a 5 speed freewheel (barely! - but without a spacer), but it would have been so close, with minimal added benefit, that I did not go there - even though I have several 5 speed cogs in the parts pins.   The driveline alignment with the spacer and 3 speed freewheel is about perfect - another reason I did not bother with the 5 speed rear hub..

mtatkow

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Re: Radmission Gearing
« Reply #7 on: February 27, 2022, 08:53:56 AM »
thought I would add a photo


Jeff_RI

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Re: Radmission Gearing
« Reply #8 on: April 13, 2022, 11:03:50 AM »
Nice job mtatkow!

I really want to upgrade from the RAD stock tensioner on my Mission1. My original tensioner failed after 500 miles, the part is not good quality. I brought my bike to my LBS and they found a good tensioner (SURLY SINGLEATOR) that they would mount to the rear hub but they could not find a hanger plate that would fit the Mission. You mentioned using one from a TREK 7100. Any ideas of where I could source a tensioner that would fit without modification? The opening needs to be 12mm?
« Last Edit: April 13, 2022, 04:38:59 PM by Jeff_RI »

J3rry

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Re: Radmission Gearing
« Reply #9 on: July 16, 2022, 11:44:04 AM »
thought I would add a photo

If you put 3 or 5 gears in the rear wheel and not change the front at all, do you think that would work?

It would be so great to have this bike be somewhat useful with no battery.

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