Head tube angle, trail and tiller
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URL: https://forum.bhpc.org.uk/forum_posts.asp?TID=5098
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Topic: Head tube angle, trail and tiller
Posted By: garryb59
Subject: Head tube angle, trail and tiller
Date Posted: 09 March 2015 at 10:27pm
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I'm sure this is an old chestnut around these parts, but just out of interest, if you're building a standard RWD SWB 700c rear, 20" front, designed for long distance road riding, what kind of combination of head tube angle, trail and tiller are you thinking of using? Do you have standard measurements that you normally adhere too? I've built around 10 bikes now, some haven't seen much of a life, but I'm still a bit confused about handling and how these things interact. At the moment I'm going to go with a basic 72dg HTA and an inch of trail...without too much tiller, say 6-8 inches or so. Lthopugh I ahveb't ridden it for 8yrs, the bike I was riding on Saturdays Audax, although nicely done, it has a wheelbase of 50inches [which was nice loaded up going down to Spain], and the front wheel is too far forward, giving a lot of tiller, and this didn't always give great handling, even though the HTA and trail were as above. I'd always kind of ignored the tiller effect, but it is important I think. I'd be interested to know what people do. |
Replies:
Posted By: Andy TS
Date Posted: 10 March 2015 at 12:13am
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Find the measurements and dimensions for optima baron and copy that. Easy to ride either loaded or unloaded tiller effect not noticeable and comfy even with seat laid right back. Happy for someone who knows there stuff to chime in now about flawed design etc but I like my bike so there 😛 ------------- Allewedder A2, Broken Optima Baron Lowracer |
Posted By: Yanto
Date Posted: 15 March 2015 at 6:19am
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Garry, i'll have a look at the Fuego and see what dimensions that has, not sure i will be able to measure head angle though, and to be honest never having built a bike, nor being that interested in specifications like that I'm not exactly sure what i would be measuring to get the angle.
Actually talking about the Fuego I must get it up for sale rather than it sitting unused in the workshop.
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Posted By: garryb59
Date Posted: 15 March 2015 at 1:39pm
Ian, thanks all the same but don't waste time on that, I'm just about to weld this thing together now anyway. I'll just get on and do it like I always have done - then see how it handles.  I want to try and get it finished before The Dean in a couple of weeks. It will be weather permitting though. [Weather permitting? I should be taking lessons in how to ride 200 miles per day, day after day regardless of conditions from Steve Abraham, colossus of the HAMR challenge, but somehow, it's not rubbing off!!] |
Posted By: garryb59
Date Posted: 01 April 2015 at 8:53pm
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Well, hardly an innovative design, and something I haven't done for 6 years, but I http://homepage.ntlworld.com/vindaloo77/100_1945.JPG" rel="nofollow - got the new bike finished last Friday. I finished at about 8pm Friday, didn't ahve time to even test ride it, put it in the car early hours on Saturday and drove over to Oxford to do the Dean 300km Audax. Apart from a fiasco with the brakes, I got round. One thing I was really pleased about this bike though, was the drive-side idler. In the past I've gone from skate boards wheels, to delrin untoothed idlers, but this time I made a terracycle-inspired toothed idler, housed around a 32mmx9mm-15mm dia bearing, with a solid stud welded to the frame and it felt really good. The power transfer felt nice and solid. It's just the engine that needs some work doing to it! It is satisfying when you build a bike, put it to the test and it holds up. It should do - steel's nice and easy to work with and it weighs a fair bit [don't ask about getting over the lumps]. The tube is basic 44mm 18g ERW. And the carbon seat I made in 2008, but never got round to using it! Question is, have I got time to replicate that in carbon before PBP? [still fence sitting about being there though]. |
Posted By: AlanGoodman
Date Posted: 01 April 2015 at 9:20pm
Looking good!!  ------------- |
Posted By: Andy TS
Date Posted: 04 April 2015 at 10:03pm
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Thought I recognised the bike. Hope you had a good ride back from your break at Winnersh ------------- Allewedder A2, Broken Optima Baron Lowracer |
Posted By: GeoffBird
Date Posted: 05 April 2015 at 10:33am
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Looks like you've gone for a steep steering head with very little offset (lots of trail) Gary - way to go in my limited experience. Like the idler - very smart. ------------- Right Time - Right Place - Wrong Speed |
Posted By: garryb59
Date Posted: 05 April 2015 at 8:48pm
Thanks for posting Andy - it's always good to put a name to a face. It was a relief when I knew you were coming from a knowledge base, I thought I was going to have to answer one of those 'what's that thing like to ride' questions [perfectly fine even though the question is], but after 270km, it's not always easy to find any spare grey matter that feels like answering the question! Sorry to hear about the Baron 
Thanks Geoff. The idler's the best bit of the bike actually! The HTA is about 72dg and the trail 50mm. All standard stuff. Might be interesting to rig up a fork with adjustable drop outs one day to see how handling is affected. It rides perfectly fine. I need to tidy up the return chain though, it might be ok to have it running along side the front fork for racing, but it's a bad move for Audaxing - especially after a wrong road has been taking and you need to double back quickly. Don't ask me how I know this Working with a cheapo MIG on ERW tube is very easy for a kitchen table DIYer like myself, but there's a weight penalty to pay. I've just put the bike on the scales and without water, tools etc it comes in at a cool 38lbs. Time to up the technology a bit! I think I like building as much as I like riding though. |
Andy TS wrote:Posted By: Karl
Date Posted: 05 April 2015 at 11:53pm
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Quote - Might be interesting to rig up a fork with adjustable drop outs one day to see how handling is affected. Think I remember correctly that Mike B did this and hence why the machines he builds have 80(ish) deg head angles, and most forks(?) don't have any rake... works a treat on the RatracerSL ( http://www.advancedvelodesign.com/ratracersl/images/ratracersl-recumbent-bike-side-view.jpg" rel="nofollow - ratracersl-recumbent-bike-side-view.jpg ) Karl
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Posted By: GeoffBird
Date Posted: 06 April 2015 at 2:07pm
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Karl, I was going to say that my experience of building bikes is that about 80 degrees works really well, as long as you don't have much tiller. But I prefer a bit more trail for a touring machine (so a bit of negative offset) - makes for more relaxed handling when you're tired. I'd go for the steepest head angle you can (up to about 80 degrees) for no more than 7 or 8 inches of tiller. A vertical head angle gives incredible low speed (walking pace) stability, but conscious movement of the steering to get it to turn into a corner, in contrast to many Dutch recumbents, with fairly relaxed head angles and little trail, which I find twitchy in a straight line and having a tendency to fall into corners in a rather unnerving way, but maybe it's just what I'm used to. All this is rather unscientific as it is difficult to change only one parameter affecting steering feel at a time, even if I'd tried to. All I can say in defence of my argument is that most people find most the bikes I build easy to ride, with the possible exception of the high racer I built last century which had a conventional head angle and offset, so not much trail
------------- Right Time - Right Place - Wrong Speed |
Posted By: garryb59
Date Posted: 06 April 2015 at 9:16pm
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I was going to mention tiller. I'm always conscious of trying to balance all these things out, so neither tiller, trail or HTA are too extreme, but the situation is being made more difficult by having handlebars really quite close to my body. However, sitting on the bike stationary and just imagining where my hands would like to be if I were to start afresh, indicates a more forward position, which would cut down the need for quite so much tiller and thus facilitate a steeper head tube angle. That will be the next job, to look more closely at the ergonomics of the handlebar position. Thanks for the feedback Geoff, really appreciate it. |
Posted By: GeoffBird
Date Posted: 06 April 2015 at 10:14pm
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Your design looks a good compromise to me Gary. You've built a few bikes - does your experience tally with mine? Has anyone else who has built and/or ridden quite a few different bikes got an opinion?
------------- Right Time - Right Place - Wrong Speed |
Posted By: legs_larry
Date Posted: 07 April 2015 at 9:04am
Having had the pleasure of Garry's company on numerous rides back in the last decade I can assure Thee Panel that after ~1100 km he had far more spare grey matter than I did. ------------- ==================== a bit ov a lyv wyr by slof standirds |
Posted By: garryb59
Date Posted: 07 April 2015 at 10:09pm
Tell you what Dave - I'm still dithering, I might be there, I might not, but I can honestly say that if I do make it to the start line in Paris in August, I will be parked among the dark side fraternity, waiting for the off, and your presence will be greatly missed. Really. You are not the reason I ride recumbents, but you are the reason I ride recumbents on Audax. [BTW, can you give me your home address, so I can send my private psychiatric bill that bears testimony to the fact :-) |
Posted By: garryb59
Date Posted: 07 April 2015 at 11:57pm
Well....problem is Geoff, I tend to come from a non-scientific background of 'not quite sure what I'm doing but I've heard that this is what needs to be done'...kind of thing. I have a decent practical aptitude, but do not possess a technical, scientific background, and let's face it, the two can obviously work well together. I've also definitely not built a bike with a HTA greater than 74dg, so your 'up to 80dg' answer is interesting, particularly when you talk about slow speed stability....and for me, that's very important! Looking at the tiller on this latest bike, It comes in at around 7". I'm not sure I'd want any more than that. Thing is: if you had two bikes, one with 80dg HTA, zero offset and 50mm of trail, and another with a HTA od 72dg, 30mm of off set and trail of 50mm would the handling charachteristics be the same? Now I rememebr the feeling - as soon as you've built one, you want to build another bike straight away !! As an aside - I've looked, but I think it's a no-goer, but is it possible in your experience to source 20g 1.3/4" - 45mm steel tubing, that would be MIGable? I've not seen anything like this that is commerically available. The best I can get is 18g 1.3/4". Second question - ever used a mandrel bender? Might they be ok for thin wall steel tubing? I'm constantly amazed how welding can make a length of steel tubing so much heavier. How does that happen? A few lap joints, bit of gusset support and it totally seems to change the weight character of a length of steel without seemingly adding much extra metal?? I've got that carbon fabric sitting here, but I still can't let go of the fact that it must be possible to build a steel bike for Audax that doesn't weigh a ton. Sure, it's not going to be light, I don't expect that....but just not quite so heavy as the 38lber that my latest offering is. Am I delusional? [Why do I even ask he question :-)] |