gearing question

[stuee147]

hi all
iv had an idea and would like to run it by everyone and hopefully get some feed back.(good or bad)

im planing a second recumbent trike build and have been looking at different gearing options and iv seen some brilliant things out there such as the Shlumpf HSD, i may be behind the times but i think its a stroke of genius the way it works.
anyway i was thinking of how can i get excellent low gears for hills but still get great high end for the flats and long runs,
so my idea is this
if i use the back end of a MTB so i have the wheel, the frame (poss suspension) and the bottom bracket. then weld my frame onto the bottom bracket, i would then cut off the pedal on the right leaving the gears intact. i would then remove the left pedal and fit a second set of gears with the pedal cut off as i did for the right. then i would fit a second bottom bracket at the front of the trike as you would see on any trike but with the gears on the left rather than the right.
i would then have a chain running round the front gear set using a standard front derailer then the chain would run down the left hand side of the trike to the rear bottom bracket and around the gears on the left, i have a couple of ideas on haw to do the gear change either a standard front derailer and have a rear derailer somewhere between the two bottom brackets to keep the chain tensioned or maybe adapt a rear derailer to do the gear changes on the rear bottom bracket. or i may just fit a single gear on the left of the rear bottom bracket any thoughts are welcome.
then the gears on the right of the rear bottom bracket and the rear wheel would be linked in the normal way.
now i know this set up would mean 3 or even 4 gear levers (unless i think of some elaborate digital touch screen gear changer ) but im not concerned with that at the moment.
but as far as i can work it in my head if i select small gear on the front set running to a large gear in the middle on the left which is connected to the right side where if i select the small gear that would drive the large gear on the wheel surely this would give me an ultra low gear for hills, and if i change it to large gear drive left small gear driving right large gear driving wheels small gear then surely this must give me an ultra high gear for flats or downhills ect..???????????

i may be completely wrong with my workings or i may have missed something either way pleases let me know as i dont have the best track record with working out gear ratios i once built a gokart with a 250cc motorbike engine and i spent hours setting up gears and chain runs ect only to find on my test drive all the gears worked grate apart from the fact it drove me backwards dont ask as i really havent got a clue how i managed it just that good i reckon
all im doing here is throwing around ideas for a cheap idea for having better gearing..

stuee

 

[mrandmrspoves]

Why not just use a Shimano Mega Range rear cassette/freewheel, and a triple on the front? Easier, less to go wrong and will give you a "Granny gear" that can get you up almost any incline.

 

[stuee147]

Why not just use a Shimano Mega Range rear cassette/freewheel, and a triple on the front? Easier, less to go wrong and will give you a "Granny gear" that can get you up almost any incline.

Iv not really decided how I'm going to go with the gears yet its more I was sitting looking at bike bits and just had the idea that it could be an option
Stuee

 

[mrandmrspoves]

[QUOTstuee147, post: 3052669, member: 34880"]Iv not really decided how I'm going to go with the gears yet its more I was sitting looking at bike bits and just had the idea that it could be an option
Stuee[/QUOTE]
They say that if you want to find the most efficient way of doing something you should ask a lazy person! :-)

 

[Rickshaw Phil]

nWhat kind of gear range are you looking for?

Having spent a while working out gear options for my current bikes and then playing round with lots of ideas for hypothetical bikes, I'd suggest utilising a rear wheel with a freehub to give a better choice of gear ratios. You could then go for something like a 48-36-26 chainset with 11-34 cassette which would give a range of approx 19 to 109.5 gear inches (this is based on a mountain bike size wheel and 1.75" touring tyre), which should get you up the majority of hills but still be pretty sprightly on the faster bits.

If you wanted a super low gear, change the chainset for a 44-32-22 and then using the same 11-34 cassette would give a range of approx 16 to 100 gear inches. Still reasonably quick at the top end but you could wind your way up practically anything.

I hope that's of some use.

Edit to add: You would obviously need a Megarange compatible rear mech and the above set ups would be pushing the limits of what it would take.

Alternatives would be a 48-38-28 chainset giving approx 20.5 to 109.5 gear inches or a 42-32-22 chainset giving approx 16 to 95.5 gear inches.

 

[raleighnut]

hi all
iv had an idea and would like to run it by everyone and hopefully get some feed back.(good or bad)

im planing a second recumbent trike build and have been looking at different gearing options and iv seen some brilliant things out there such as the Shlumpf HSD, i may be behind the times but i think its a stroke of genius the way it works.
anyway i was thinking of how can i get excellent low gears for hills but still get great high end for the flats and long runs,
so my idea is this
if i use the back end of a MTB so i have the wheel, the frame (poss suspension) and the bottom bracket. then weld my frame onto the bottom bracket, i would then cut off the pedal on the right leaving the gears intact. i would then remove the left pedal and fit a second set of gears with the pedal cut off as i did for the right. then i would fit a second bottom bracket at the front of the trike as you would see on any trike but with the gears on the left rather than the right.
i would then have a chain running round the front gear set using a standard front derailer then the chain would run down the left hand side of the trike to the rear bottom bracket and around the gears on the left, i have a couple of ideas on haw to do the gear change either a standard front derailer and have a rear derailer somewhere between the two bottom brackets to keep the chain tensioned or maybe adapt a rear derailer to do the gear changes on the rear bottom bracket. or i may just fit a single gear on the left of the rear bottom bracket any thoughts are welcome.
then the gears on the right of the rear bottom bracket and the rear wheel would be linked in the normal way.
now i know this set up would mean 3 or even 4 gear levers (unless i think of some elaborate digital touch screen gear changer ) but im not concerned with that at the moment.
but as far as i can work it in my head if i select small gear on the front set running to a large gear in the middle on the left which is connected to the right side where if i select the small gear that would drive the large gear on the wheel surely this would give me an ultra low gear for hills, and if i change it to large gear drive left small gear driving right large gear driving wheels small gear then surely this must give me an ultra high gear for flats or downhills ect..???????????

i may be completely wrong with my workings or i may have missed something either way pleases let me know as i dont have the best track record with working out gear ratios i once built a gokart with a 250cc motorbike engine and i spent hours setting up gears and chain runs ect only to find on my test drive all the gears worked grate apart from the fact it drove me backwards dont ask as i really havent got a clue how i managed it just that good i reckon
all im doing here is throwing around ideas for a cheap idea for having better gearing..

stuee

Seat position would be high due to the chain/nads interface situation. Why not a 3spd Hub with 5/6 screw on freewheel and a front triple.

 

[stuee147]

Seat position would be high due to the chain/nads interface situation. Why not a 3spd Hub with 5/6 screw on freewheel and a front triple.

yea i hadn't thought of the seat, even if i dropped the rear bottom bracket that would then put that to close to the ground.
i was thinking lastnight that if i fitted a single on the left with a triple on the front. and if i make the single the same teethe as the middle front then that would give me a 1:1 ratio and then i use rear set as normal but then i have a choice of a larger or smaller front gear to give me different ratios depending if im after ultra low for hills or extra high for flats. that would help a bit with the clearance on the seat but i think im gona have to do some scale drawings to find where the chain will run and what clearances i have for the seat.
i dont quiet get what you mean by 5/6 screw o freewheel ??

stuee

 

[raleighnut]

yea i hadn't thought of the seat, even if i dropped the rear bottom bracket that would then put that to close to the ground.
i was thinking lastnight that if i fitted a single on the left with a triple on the front. and if i make the single the same teethe as the middle front then that would give me a 1:1 ratio and then i use rear set as normal but then i have a choice of a larger or smaller front gear to give me different ratios depending if im after ultra low for hills or extra high for flats. that would help a bit with the clearance on the seat but i think im gona have to do some scale drawings to find where the chain will run and what clearances i have for the seat.
i dont quiet get what you mean by 5/6 screw o freewheel ??

stuee

Someone has already done this and its 3 (on front) x 5/6 speed screw on freewheel to a 3 on SA hub gear giving 45 or 48 spd but it is a bit of a faff' Possible though and with low low low you could twiddle up just about anything.

 

[TheDoctor]

SRAM dual-drive.
That's a 3 speed hub with a 9 speed cassette for 27 gears, all of them usable. Get a triple too, if you must, and that's 81 gears.

 

[byegad]

I've had a Dual drive hub (3 speeds) with cassette (9 speeds) and triple up front (3 speeds) Multiply 3x9x3=81 on my standard Azub-4 bike. The builder uses it all of the time for the Czech Mountains. Range was 15-150", the 15" is about the at the lower limit of balancing speed on a two wheeler, while the 150" top was good for 50mph and still pedalling. If you had the hill to go down and the pair to do it!

Put a similar set up on a trike and you can get a lot lower (No chance of falling off!) I'd probably go for 10-100" as 100" is good for over 30mph and you'd only ever use it down hill.

My Catrike Trail runs 22-34-48 to 11-34, on skinnyish 20" (actual diameter measures 19") tyres this gives me 12-83" which gets me (A manifestly less then svelte and only fairly fit 62 year old.) up 25% without stopping and 33% with regular stops to get my breath! The 83" is a tad* low for normal rolling roads where belting down slight hills to get a run at the next upward one is routine. However I ride the Trail in Weardale, North York Moors and Yorkshire Dales and racing down hill is too easy with Sir Issac's discovery providing the power and even the highest speed doesn't carry you too far up the next 20+% so top isn't an issue.

My QNT gear range is 14-100" and my Kettwiesel's is 15-96". Neither is geared low enough for really steep hills, and both are a deal heavier (Thanks to innate and carried weight and my use of a Streamer Fairing) than the 32lb Trail. Both are great on rolling countryside having the ability to easily pedal past 30mph early in a descent before gaining more speed due to gravity. (I've clocked on GPS 50mph dead on both at various times in Northumberland.)

My point? There are relatively cheap options for lots of gears and super wide gear range already. Rather than add extra layers of complication stick to a simpler design.