Author Topic: Setting boom length on trike  (Read 603 times)

Setting boom length on trike
« on: December 28, 2019, 07:17:03 pm »
Is there a trick to setting up how far away you set the BB on a recumbent (trike in my case)? The seat has a fixed back and the BB is movable.

I have just set my trike up in the garage on the rollers (partially to see how different it is, and partly to see if it helps with a hip issue which is worsened by closing my hip angle), but I don't know if sitting in a different place means that there is a different technique for working out leg length on a recumbent?

Hopefully I'm going to try to sort out my trike so I can actually use it outside in 2020, and if it does help my hip out then I might look into building myself a 2 wheel recumbent, but I don't want to screw up the


Kim

  • Timelord
Re: Setting boom length on trike
« Reply #1 on: December 28, 2019, 07:29:43 pm »
Heel of fully extended leg on the pedal is a good starting point, much as it is on an upright.  (KOPS is right out :))

From there, it's trial and error: Your pedalling technique is liable to be different in the recumbent position (I find that I ankle more, especially if the bottom bracket is relatively low).  Also most riders tend to settle in the seat after they've been riding for a while, so the optimal extension half an hour into a ride might be a little bit longer than when you first get on.

Depending on how the seat is attached, changes in the seat angle may or may not affect the required boom extension.  HPVelotechnik style mountings pivot the seat around your hip joint to avoid this (ostensibly to simplify on-the-fly seat adjustment for different styles of riding), but most will pivot around the lower seat bracket.

As on an upright, if your knees hurt, the boom is probably too short.  If you feel overextended, get Achilles pain, or find yourself sliding too far down in the seat, it's probably too long.
Careful, Kim. Your sarcasm's showing...

Re: Setting boom length on trike
« Reply #2 on: December 28, 2019, 07:50:17 pm »
Thanks - that's a really good start! :)

Re: Setting boom length on trike
« Reply #3 on: December 29, 2019, 06:25:23 pm »
I tried it a bit with it set up as I left it before.  After about 10 minutes pedalling I adjusted it about an inch further away - much closer to heel on pedal with a straight leg. I can't actually put my heel on the pedal with my leg straight and the crank out straight ahead, as the back of my leg hits the crossbar!
My hamstrings are noticeably more fatigued than if I had been riding the upright bike (especially seeing as I only did 30 minutes or so). I assume that's normal and "bent legs" will bring them in line with my fitness?  How long does that take, if I ride every couple of days on the trainer for around an hour? I could ride at 130-150W fairly comfortably at ~90 rpm, and spin up towards 150rpm if I tried. The only other weird thing was a slight forward and backward rocking motion - this might just be down to a 20" wheel not working so well with the rollers...
You can see some pictures of the setup (and the ride data itself) here: https://www.strava.com/activities/2964750923

Re: Setting boom length on trike
« Reply #4 on: December 29, 2019, 06:53:28 pm »
Yes, hamstrings and Gluteous will feel that extra burn / ache till you've got more recumbent miles in the legs. I'm going through the same at the moment on my new recumbent having spent late 2019 mostly on my road bike.  I'm about five weeks ahead of you and legs still adapting.  I'm getting stronger / faster but still getting the leg burn. It does go away but can't remember how long it took on my first recumbent. Just keep plugging away.
If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

Re: Setting boom length on trike
« Reply #5 on: December 29, 2019, 06:59:50 pm »
Yes, hamstrings and Gluteous will feel that extra burn / ache till you've got more recumbent miles in the legs. I'm going through the same at the moment on my new recumbent having spent late 2019 mostly on my road bike.  I'm about five weeks ahead of you and legs still adapting.  I'm getting stronger / faster but still getting the leg burn. It does go away but can't remember how long it took on my first recumbent. Just keep plugging away.
Are you moving to recumbents permanently, or are you planning on mixing and matching? I have no intention of switching permanently, so if it's going to take many months and mean I'm less capable on my upright bikes afterwards I might need to rethink my strategy a little.

Re: Setting boom length on trike
« Reply #6 on: December 29, 2019, 07:28:54 pm »
Yes, hamstrings and Gluteous will feel that extra burn / ache till you've got more recumbent miles in the legs. I'm going through the same at the moment on my new recumbent having spent late 2019 mostly on my road bike.  I'm about five weeks ahead of you and legs still adapting.  I'm getting stronger / faster but still getting the leg burn. It does go away but can't remember how long it took on my first recumbent. Just keep plugging away.
Are you moving to recumbents permanently, or are you planning on mixing and matching? I have no intention of switching permanently, so if it's going to take many months and mean I'm less capable on my upright bikes afterwards I might need to rethink my strategy a little.

I want to move full time to recumbent for my audaxes and long distance rides. I find the best way to adapt as quickly as possible is to go exclusive recumbent for a period. So every ride is recumbent. I have a road bike and Brompton also. I'll reintroduce them once I feel I'm adapted enough.  I didn't find it affected my road bike performance too much at all, when I did similar in late 16 / early 17, but depends on what you mean by performance. There's still a lot in common such as the aerobic engine and the rest of the major leg muscles shared with a road bike.

If you are worried about losing your toad bike performance then just keep riding that as well.  It'll mean your improvements recumbent will take longer, but unless there's a pressing need I'd say you'd be ok with that.

My road bike will be more where I want to take in some easy off road as well, as it can take up to 38mm tyres.

If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

Socks

  • FFCT rally, France 2012
Re: Setting boom length on trike
« Reply #7 on: December 29, 2019, 08:02:03 pm »
What Phil W said.  I've gradually moved over to recumbents over the last three years because uprights were getting so painful on 'long' rides (200k is a long ride for me).  For a while I used both uprights and recumbents on audax rides so I suppose it might have taken a bit longer for my leg muscles to get used to the recumbent.  Still use uprights for short trips but now my legs have acclimatised the recumbent is so much better on longer rides.

Re: Setting boom length on trike
« Reply #8 on: December 29, 2019, 08:23:43 pm »
I don't really do long rides as family life gets in the way. :(
This year I was doing TTing and CX. I quite fancy doing some gravel stuff on a recumbent (yet to be built) if I get on with them, but I'd also like to do CX again next year.

Re: Setting boom length on trike
« Reply #9 on: December 30, 2019, 01:03:53 pm »
Keep riding your CX bike as well as the trike / new recumbent and you'll be fine. 
If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

Re: Setting boom length on trike
« Reply #10 on: January 01, 2020, 12:57:52 pm »
I find that I'm pedalling with my feet at 30 degrees to the vertical. This is meaning I don't really use my calf muscles at all and the leg extension feels like it's too short. Should I be trying to change how I'm holding my feet, or is this normal (ish) and I should be extending the boom a bit more?
The back is fixed (bolted to the frame).

Also, I'm using my pedal based power meter, and it's soooo much harder than on the upright bikes. I can't really hold 150-170W for 45 minutes on the trike (either having breaks or just riding below the target wattage). That would be an easy endurance ride on the upright bike - something to fill in a day when I have intensity elsewhere and I'm short of time. Compare these 2 rides:
Trike:
https://www.trainerroad.com/career/duncanm23/rides/69494619-carter
Upright:
https://www.trainerroad.com/career/duncanm23/rides/66863609-carter

Sure, power delivery is a bit different, because one is on rollers and one on a smart trainer, and heart rate is much of a muchness, but it just feels soo hard on the trike. Also, while I can spin up to 400W, or hold 250 for a minute or so, it feels so much harder to do that on the trike. Drivetrain losses are not a factor in this - I assume it's just the whole "bent legs" process?

RichForrest

  • T'is I, Silverback.
Re: Setting boom length on trike
« Reply #11 on: January 01, 2020, 01:31:27 pm »
Don't worry too much just find what feels comfortable at the minute. You will find as you get recumbent fitter you will adjust it again.
I've been riding recumbents for a few years now and still change the boom length if it feels like I need to.

Dropped the seat on my Bacchetta a notch recently to match the position on the CHR and of course had to change the distance.
Find a position where it's comfortable to ride normally, you will move about on the seat when you put power on.
I find I purposely slide forward on the seat when I need to put more power on for hills/sprinting etc.

I had almost a year of riding the fixed upright and going back to the recumbent felt like the seat needed moving a lot.
Within a week I was moving it again  ;D


Re: Setting boom length on trike
« Reply #12 on: January 01, 2020, 05:38:27 pm »

Also, I'm using my pedal based power meter, and it's soooo much harder than on the upright bikes. I can't really hold 150-170W for 45 minutes on the trike (either having breaks or just riding below the target wattage). That would be an easy endurance ride on the upright bike - something to fill in a day when I have intensity elsewhere and I'm short of time. Compare these 2 rides:
Trike:
https://www.trainerroad.com/career/duncanm23/rides/69494619-carter
Upright:
https://www.trainerroad.com/career/duncanm23/rides/66863609-carter

Sure, power delivery is a bit different, because one is on rollers and one on a smart trainer, and heart rate is much of a muchness, but it just feels soo hard on the trike. Also, while I can spin up to 400W, or hold 250 for a minute or so, it feels so much harder to do that on the trike. Drivetrain losses are not a factor in this - I assume it's just the whole "bent legs" process?

Part of the bent legs process.  I have a smart turbo. I did a ramp test on my new recumbent about 5 weeks ago.  This revealed a FTP about 39 watts below what I was on my road bike start of Jan 19.  After five weeks I am now within 19 watts of my road bike figure of last year. What I might do tomorrow is a ramp test on the recumbent in the morning and ramp test on road bike in evening to see exactly how my power compares between the two. Both bikes use the same turbo wheel. But essentially keep riding the trike and you’ll close the power gap between them.
If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

Re: Setting boom length on trike
« Reply #13 on: January 02, 2020, 09:27:32 pm »
Well my recumbent FTP as of today is now 2 watts less than my road bike same time last year. Didn't get a chance to test road bike as well this time, but might try that next week. But I'm very happy as I'm starting from a similar fitness level as same time last year on road bike.  Starting to push heart rate but definitely strength of legs which are the weak link at the higher power levels.  Good job strength is priority on the next part of my regaining recumbent fitness plan.
If you don’t make time for exercise now, sooner or later you’ll need to make time for ill health.

Blodwyn Pig

  • what a nice chap
Re: Setting boom length on trike
« Reply #14 on: January 03, 2020, 12:25:12 am »
Now presumably, it matters not, whether it's a trike or bike , boom length setting should be the same? Or am I missing something, just so that I know for future reference.

RichForrest

  • T'is I, Silverback.
Re: Setting boom length on trike
« Reply #15 on: January 03, 2020, 05:04:35 am »
If it has the same seat on both then yes.
A more upright seat will be different to a laid back one.
Same as a euro mesh one on my Bacchetta would be at a different distance to a recurve or a fiberglass hardshell type.

Blodwyn Pig

  • what a nice chap
Re: Setting boom length on trike
« Reply #16 on: January 03, 2020, 08:16:58 am »
If it has the same seat on both then yes.
A more upright seat will be different to a laid back one.
Same as a euro mesh one on my Bacchetta would be at a different distance to a recurve or a fiberglass hardshell type.

Yes, I actually meant the procedure would be the same.

Re: Setting boom length on trike
« Reply #17 on: January 04, 2020, 12:46:54 pm »
If it has the same seat on both then yes.
A more upright seat will be different to a laid back one.
Same as a euro mesh one on my Bacchetta would be at a different distance to a recurve or a fiberglass hardshell type.

Yes, I actually meant the procedure would be the same.

YES