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Bob 
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Joined: 06 June 2022 Location: Derby Status: Offline Points: 27 |
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 Posted: 12 July 2022 at 4:52pm |
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I am using freewheels at the moment with the pawls stripped out - my only concern is this solution is quite heavy.
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Bob Scothern
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Bob
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Posted: 12 July 2022 at 4:57pm |
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I am pondering on the question of making a FWD fixed bottom bracket bike for which I will need a medium sized pulley ,maybe a 34t rear sprocket .
I have stripped out a Shimano freewheel which holds an 8 speed cassette,so it rotates both ways ,but again the solution appears to be quite heavy
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Bob Scothern
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stormbird
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Joined: 10 November 2005 Location: United Kingdom Status: Offline Points: 605 |
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Posted: 31 July 2022 at 9:58pm |
Toothed are considered quieter and longer lasting than a pulley as most non-cycling pulleys are not designed for bicycle chain. A lighter solution is to cut down the right hand threaded BB shell and screw on a single speed free wheel with the pawls removed. You will still probably need a chain keeper and some light side plates to stop the chain coming off. The worst scenario is free wheeling on a bumpy road where there is little or no chain tension. If twisting chain FWD the next worst scenario is pushing it backwards and trying to steer it  Paul
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Bob
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Posted: 01 August 2022 at 8:36am |
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Thanks for your comments - I have done exactly as you describe, that is used a free wheel with the pawl removed for the power side of my first homemade recumbent. The only difference is I screwed it onto a wheel hub which I then cut down to size to fit on the bike.
Hoping to go to the Ashbourne meet in August to pick up some ideas. cheers Bob Scothern
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Bob Scothern
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stormbird
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Joined: 10 November 2005 Location: United Kingdom Status: Offline Points: 605 |
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Posted: 01 August 2022 at 3:38pm |
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Bob Sorry it was the 8 speed bit that confused me , I was thinking you were using the whole of a cassette screw on FW ! Hmm Darley Moor maybe do-able , if I can get a pass out from the higher domestic authority.  Could bring my tilting Python trike along ? Already running very close to the wind being to Holland this year for a week AND doing LEL a volunteer silly NOT riding it ! Paul
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Bob
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Posted: 01 August 2022 at 4:07pm |
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Paul
first ,I have my pass out and really looking forward to the Ashbourne meeting. Now ,to address the confusion 1 - I have built my first SWB recumbent with a conventional rear wheel drive. For this bike I used a single speed freewheel and stripped out the pawls. 2 - my next project is to be a FWD FBB recumbent. The chain must turn through 90 degrees in the route down to the front wheel. I have a couple of ideas about how to mount the large pulley at the top of the front fork. One would be to use a rear wheel hub but strip out most of the cassette save the largest 34t chainring. Another would be to use a front wheel hub and bolt onto the flange a large pulley. Another idea would be to laser cut a set of discs and rivet them together to form a pulley. I would weld a stub axle to the side of the fork. The machine in your picture looks interesting. This is exactly why I want to go to the meeting, camera in hand. One problem I currently do not know how to address. That is a swing arm bush assembly. They are used extensively on MTB rear suspension bikes. I simply want to make a swing arm pivot. I can drill and ream holes but I do not know how to source a set of bits to make a close fitting bearing assembly. Yes I can source bearings, but the matching shaft is my problem. Fitted bolts maybe? I do not own a lathe - at the moment!
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Bob Scothern
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stormbird
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Posted: 01 August 2022 at 10:04pm |
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Bob A simpler solution would be to use M12 rod end bearings ? The pivot would be M12 also , these are used vertically on my Pythons for the last 9 years. They have not failed in use , however they need changing every spring as riding through the winter and inadequate shielding from the elements causes premature death by grinding themselves away   They can be seen here Paul
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Bob
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Posted: 01 August 2022 at 10:37pm |
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Paul - I will look into that as a solution. I found a website selling Brompton suspension rubbers for a reasonable price last year, which in combination with a pivot would give me rear wheel suspension with a little bit of damping.
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Bob Scothern
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stormbird
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Posted: 02 August 2022 at 7:51am |
Bob Where was the site @ for the rubbers ? I am contemplating rear suspension for the trike after a fairing/back box for the camping gear instead of towing a trailer or panniers. Currently CAD'ing it as I type :-  Have you found this ? http://www.python-lowracer.de/construction.html From 4 onwards it shows how to suspend a single rear wheel with an elastomer. My problem is deciding whether it would work on a trike where there are greater lateral forces ? Paul |
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Bob
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Posted: 14 October 2022 at 5:06pm |
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Geoff
typing into Google " jig built recumbent" I came across your T7. I wonder if I could ask you a few questions 1) the front suspension - I cannot work out where the pneumatic spring sits 2) you mention stressing a high tensile bolt. This of course assumes you have a load case; so I was wondering what insight you have into load cases. 3) the rear dropout detail. Looks very compact, so I am assuming it is a brased detail? 4) do you have any details of the drive line regards Bob Scothern - retired mech eng. Currently building a jig to make a bike similar to the p38 Lightening
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Bob Scothern
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Bob wrote: