LouB 

Has anyone ever tried to mount a smaller chain wheel on a Raleigh "Heron" cottered crank. I dont want to give up a cool vintage crank on my Lenton, but need more gear going up hills than my current 49/46 (half-step)crank gives me. Thought if I could adapt a Raleigh single 50T Heron and add a 40T ring, that might make riding my Lenton a bit friendlier. Currently running Benelux RD and FD. Figured, that if the mod could be done I'd need to replace the FD. Having to replace the read would be a no-go for me. Its just too cool imho.
Thoughts please.

3speedslow

Okay, so by saying you don't want to replace the rear dr, you mean you do not want to consider a freewheel change? What is the upper limit of the dr you have on it now?

You have an interesting inquiry. Looking forward to the responses!

juvela

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Since your chainwheels are riveted it would mean grinding of the rivets and replacing them with bolts.

Given the bolt circle on the outer chainwheel it does not look like you could go much smaller.

Alternately, you could search for another Raleigh marked right arm with a smaller inner.

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juvela

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Pic assist for other respondents -



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dweenk

Go larger at the rear, that is easier and non-destructive.

rhm

Is that the right crank, really? I know the later version Lenton Grand Prix has that crank, but the earlier one had a Williams crank with herons. The smaller ring is 46t.

If you have one of those, it may be possible to drill and tap the three arms to fit a 36T ring with 116mm bcd.

juvela

Nice idea when capacity present. In this case we have a Benelux Mark 7 stern mech with a largest cog capacity of 22T.



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BigChief 

I suppose you could put your original wheel aside and build up a new one with an AW hub with twin cogs. The internal gears would give you a 25% decrease in underdrive and a 33% increase in overdrive.

1989Pre 

I have a Raleigh-branded Nicklin 46-49. It is swaged, so for me, anyway, modifying it is out of the question. What I did was had a 28T low gear put on my Maillard 4-sp freewheel. It came from a later Sachs 5-sp.
Getting my Benelux Mk7 (which is rated at 22T) to accept the big low gear may take some doing, but I had it going for a while, and I think the chain was too short. I'm going to try again with a longer chain.
I've seen pics of bikes with MK7's and 28T low cog, and like I say, I've done it so I know it's possible. I just have to figure out if I can adjust it to work reliably long-term.
You can find vintage 46-40T cranks, so if you have to swap, do what you have to do, but I can handle the 46T-28T low gear and if the hill is too steep, I'll just get off the bike and take a relaxing walk to the top of the hill.

rhm

I agree with @1989Pre, that the Cyclo can be made to shift to a 28t cog. The derailleur on my Lenton GP was a bit bent (as is usually the case) and I didn't have the 4-sp freewheel anyway, so I put a 14-28 five speed on there. The derailleur shifted across all four bigger cogs no problem, and once in a while I could coax it into the 14t. Since the latter was rarely necessary, I thought it a good compromise.

juvela

What about the wrap? Did you find the Mk. VII to have adequate wrap with the larger cog installed?

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1989Pre 

I don't know. My shop did the work, and it worked while it was working, so I didn't check it. I had a pulley pin issue later on, so I took the Mk7 off and ran a Suntour (@2000) for a bit. I'm waiting for the pins in the mail, but these pics might help...It's all I've got right now.
In the second pic, I am pushing the cage forward until it meets the adjusting screw. If i don't get the recommended three chain rivets visible on 28T, it looks like I'll get at least two. I'll let you know in about a week and show the chain wrap I get.

1989Pre 

Here are a couple of pics of a Raleigh with Cyclo Mk7 and 28T low gear. I don't know the owner, but it appears he's satisfied with the setup:

1989Pre 

Here are a a couple of photos of a Claud Butler with Cyclo Mk7 and a 28T low sprocket.
I don't know the owner, but it appears he's satisfied with the set-up:
In photo #3, I can't guarantee that that is a 28T.

juvela

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Thanks very much for the response. I learns me somethin' with each visit to the forum.

With regard to the gold bike suspect large cog more in the 24T-26T range than 28T.

When your parts come in and you have everything re-installed will be interested to hear if it is able to shift into and out of the small/small & large/large combinations well. Suspect that determining a chain length which will permit this may be a challenge. One can fine tune chain tension in limited measure by moving rear axle in dropouts.

Thanks again!

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1989Pre 

Yeah, I sure will. The only challenge that I see is what RH referred to: getting the cage to swing all the way out to grab the small cog (that's why I have a spacer on there).

juvela

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Manufacturer's instructions with parts drawings for the Benelux Mark 7 rear mech:

https://www.peterbrueggeman.com/cr/ca...elux_mark7.pdf

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juvela

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1989Pre has begun an new thread on the fine tuning of the Benelux Mark 7 rear mech here:

https://www.bikeforums.net/classic-vi...-tweaking.html

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