Help with frame related questions

[Bicycle Repair Man]

Look at the examples of <REDACTED>, <REDACTED> or <REDACTED>

Eh !!

DY, (reasonable grumpy old sod)

[SteelRules]

do you have an opinion about curves vs straight seat stays? Do you think choosing a frame with curved seat stays increases the comfort (all other things being equal) or is it just a gimmick?

Hi Arnaud,

I would guess that curved seat stays would take any harshness out of the back end. Cant say for certain as a) I have never ridden such a frame and b) I have never made such a frame.
Best advice I can give is try and get a ride on one and see what you think. If it suits your style of riding then fine !!

Cheers

Dave Yates

In line with the question, is Reynolds 531 the only one amenable to be used for curving seat stays and chain stays?
Reynolds 725 could potentially be employed as well if desired?

Probably at some point we need to start off the topic of frame geometry, trade offs and compromises.
Steeper angle in seat tube (76 degrees) for flats or time trials or shallower angles for climbing (73 degrees)?
Why one should favour one discipline and not the other?
So many things I do not know...
Thanks for insightful comments,
SteelRules

[Bicycle Repair Man]

is Reynolds 531 the only one amenable to be used for curving seat stays and chain stays?
Reynolds 725 could potentially be employed as well if desired?

531 stays are no longer listed by Reynolds. 725 stays are heat treated and thin and therefore totally unsuited to bending, they will simply crumple. 525 stays of a suitable wall thickness would bend if you really wanted to. I do so regularly laterally to increase clearance for big tyres, but I have never done so longtitudinally for "comfort" or "fashion"

[Doosh]

Hi Dave,

Just wondering if there's a rider weight limit for a 753R frame with 753 forks?

Cheers.

[SteelRules]

Hi Dave,

Hopefully you are having a nice week and are not too tired.

My question today is about what heat treatment adds to the steel tubes.
Ok, Reynolds 853 has added strength and added resistance over 631 due to heat treatment => quoted from Reynolds website
Question: The strength comes from increased elasticity of the tubes, like they rebound more after an impact?
If the above is correct, then how on earth 631 is more comfortable than 853?

Also, the air hardening quality of tubes has nothing to do with heat treatment, counterexample being 631, correct?

When joining tubes with lugs, is it attainable to force melted brass through the mitered tube joints to achieve some form of fillet brazing?

Many riddles...
Many thanks, Mr Yates for your time and patience.
SteelRules

[Bicycle Repair Man]

Hi Dave,

Just wondering if there's a rider weight limit for a 753R frame with 753 forks?

Cheers.

Hi Doosh

Too many variables to give a definitive answer. Riding style has as much to do with it as the weight of the rider. Another factor is how well the frame is made. You can take the best tubeset in the world but build it badly and it will be a rubbish frame (believe me, I have seen a few !!!). Incidentally, after the first few frames I rarely built 753 forks, too stiff, rattled your eyballs out. I built lots of 753 frames for the Pros in the 80's, some big strong lads, none AFAIR  failed.

Best I can do

Cheers

Dave Yates

[Bicycle Repair Man]

Hi Dave,

Hopefully you are having a nice week and are not too tired.

My question today is about what heat treatment adds to the steel tubes.
Ok, Reynolds 853 has added strength and added resistance over 631 due to heat treatment => quoted from Reynolds website
Question: The strength comes from increased elasticity of the tubes, like they rebound more after an impact?
If the above is correct, then how on earth 631 is more comfortable than 853?

Also, the air hardening quality of tubes has nothing to do with heat treatment, counterexample being 631, correct?

When joining tubes with lugs, is it attainable to force melted brass through the mitered tube joints to achieve some form of fillet brazing?

Many riddles...
Many thanks, Mr Yates for your time and patience.
SteelRules

You again

I am neither a metalurgist nor a theoretical engineer ie one who does numbers rather than getting his hands dirty  . I take what the tube manufacturers provide and design frames based on experience and feedback from the many thousands of customers that have passed my way. In my experience both as a rider and as a builder, heat treated tubes make for a more rigid structure and hence appear to move less under the stresses of riding. All the 853 and 753 frames I have posessed felt more like riding on a razor blade than a sofa. The 531, 653, 631 frames have all felt less like the former and leant towards the latter. The "feel" of a bike to any rider is very much a function of experience ie what you have ridden before. The term "comfort" is a very subjective term. My background is road racing and I feel happiest on a bike at the "sharper" end of the scale so what is fine for me to ride long audaxes on to someone else would be too harsh.

You are correct that the air hardening is independent of the heat treatment, it is a property of the alloy.

Regarding the question on lugged joints. A properly brazed lugged joint has brass or silver all the way through the joint so that the two tubes are "stuck" together. The strength of the joint is in the fit of the mitre and the penetration of the joining medium into that mitre. As long as this fit and penetration is achieved then you could wrap the joint in baked bean can and it would stay together. A common misconception is that the tube is stuck to the lug and the lug provides structural strength. The lug simply holds the tubes in place to allow them to be brazed. The brass / silver is not "forced" into the  joint but flows by capillary action, given that the joint area is hot enough ie melting point of the joining medium. If you section a joint ie cut it through the centre you should find brass all the way through so it is visible inside the tube  that forms the leg of the "tee". To ensure this is the case I normally set up the joint so that I am feeding brass in at the high point and pulling it through the joint with the torch so it appears at the low point then work it round the joint always feeding in at the higher point.


Cheers

Dave Yates

[Doosh]

Hi Dave,

Just wondering if there's a rider weight limit for a 753R frame with 753 forks?

Cheers.

Hi Doosh

Too many variables to give a definitive answer. Riding style has as much to do with it as the weight of the rider. Another factor is how well the frame is made. You can take the best tubeset in the world but build it badly and it will be a rubbish frame (believe me, I have seen a few !!!). Incidentally, after the first few frames I rarely built 753 forks, too stiff, rattled your eyballs out. I built lots of 753 frames for the Pros in the 80's, some big strong lads, none AFAIR  failed.

Best I can do

Cheers

Dave Yates

Thanks Dave, it's a Vernon Barker/MB Dronfield frame. Hopefully I'll be ok at 100kg, should be around 90 though 

[Bicycle Repair Man]

Thanks Dave, it's a Vernon Barker/MB Dronfield frame. Hopefully I'll be ok at 100kg, should be around 90 though 

By my calculations thats around 15 stone, should be fine, Vernon built good stuff, knew what he was doing.

Cheers

Dave Yates

[eck]

Vernon built good stuff, knew what he was doing.

That's a relief: I've just had a crack in my Airborne Zeppelin ti frame repaired by Vernon. Only £35, and a very tidy job he's done.

[Biggsy]

Re: http://yacf.co.uk/forum/index.php?topic=59485.0

Any thoughts, Dave, on Arno's custom frame that arrived with a fatter down tube than asked for?  Will it be "uncomfortable"?

[Ian H]

Hello Dave,

Leading on from your explanation of lugged joints, I was wondering how much of a fillet you actually need round a lugless joint. I'm thinking of a well-known frame builder whose fillet brazing was immaculate (as he himself would tell everyone), but who used a considerable amount of metal on the joints, especially at the head-tube. (I know a couple who ordered a machine and lied to him that it was for racing so he wouldn't build it so heavily).

Purely for curiosity, and only if you have the inclination to answer.

[RichMoss]

Ok, Reynolds 853 has added strength and added resistance over 631 due to heat treatment => quoted from Reynolds website
Question: The strength comes from increased elasticity of the tubes, like they rebound more after an impact?
If the above is correct, then how on earth 631 is more comfortable than 853?

Cheers

Dave Yates

I hope you don't mind me butting in here with a reply to SteelRules: I looked at the Reynolds website and can't see the exact quote. I wonder if you are confusing Elastic Modulus and 'elasticity'. A higher elastic modulus means the material is stiffer (for a given stress, it deforms less). The words elastic and elasticity just means that when you remove the stress that is deforming something, it recovers its original shape. Elastic modulus is also known as Young's modulus.
The website refers to a higher yield strength - the yield strength is that point where the material deformation changes from elastic to plastic - that is, the material doesn't return to its original shape but deforms permanently.
Richard

[Bicycle Repair Man]

Hello Dave,

Leading on from your explanation of lugged joints, I was wondering how much of a fillet you actually need round a lugless joint. I'm thinking of a well-known frame builder whose fillet brazing was immaculate (as he himself would tell everyone), but who used a considerable amount of metal on the joints, especially at the head-tube. (I know a couple who ordered a machine and lied to him that it was for racing so he wouldn't build it so heavily).

Purely for curiosity, and only if you have the inclination to answer.

Hi Ian

Back in the day, when men were men and brake cables came out of the top of the levers, I built a TT frame for a certain J Waugh. He won a Commonwealth Games Gold Medal in the TTT on this frame. It was made of 753 built lugless with  55% silver solder. The fillets were minimal, about 3mm radius mainly because that stuff is so fluid that it is impossible to make them bigger. I did this for a number of reasons, first to get the frame as light as possible, secondly as a showpiece for the business and thirdly because "they" said it couldnt be done. The frame survived and is still going strong.
As I said in the previous post the strength of the joint is in the fit of the mitre and the penetration of the brass/silver. Peugeot used to make a "sports" bike with no lugs and no visible fillet. We sold loads of them in the shop at Steels and AFAIK none of them broke. The mitres were machine cut to close tolerance, the joint was done by utilizing a pre placed coil of brass in the tube and heating the whole lot with monster torches so the brass melted and ran into the joint. They claimed an "internal fillet" was formed, I never cut one open so I dont know for certain but the claim seems reasonable.
I have never liked huge fillets, they are not necessary and look slightly ugly. They require more heat and more brass to no mechanical effect and take more cleaning up and finishing. Not a lot going for them really !!!
I normally try and end up with fillets 10-12 mm wide which, to me, looks about "right" However at the end of the day "beauty is in the eye of the beholder"

Cheers

Dave Yates

[Bicycle Repair Man]

Re: http://yacf.co.uk/forum/index.php?topic=59485.0

Any thoughts, Dave, on Arno's custom frame that arrived with a fatter down tube than asked for?  Will it be "uncomfortable"?

My apologies Biggsy, I missed this one.
Just read through the thread and I have to agree with those who said "talk to the builder". I hate having dissatisfied customers and will try and do everything to resolve any such situation. In terms of what difference the slightly larger down tube would make, I have no experience of Titanium as a frame material so my comments are not particularly valid. If this were a steel frame then I suspect that the difference in "feel" would be minimal. The lateral stffness of the frame would be slightly greater but you would have to ride two otherwise identical bikes to notice any difference at all and a lot of that would be subjective. How any bike (frame) is perceived by the rider is largely a function of experience ie what you have ridden before, how your brain works, how much influence "mates" and forums have had etc. Take one bike and three riders from different backgrounds and you will get three different assesments of the bike. Some can take almost any bike and ride it whilst others agonise over the finest detail that has no bearing on the function of the bike at all. We are all different and IMHO it is the job of the builder to get inside the head of the customer, read his/her dream and turn it into a reality that matches the dream as closely as possible.

Cheers

Dave Yates

[Rhys W]

I remember those Peugeot frames, I'm sure they were called "inexternal" or something. Interesting to learn the engineering facts behind the marketing. 

[Bicycle Repair Man]

I am guessing that a frame with low bottom bracket (8cm drop and 26cm height)
with seat tube angle of 72 degrees and head tube angle of 73 degrees
plus curved fork blades with rake in the interval 4.5-5.0cm ought to be comfortable.

The main triangle for a large sized frame (59-60) could be made tighter by lowering the horizontal top tube 2cms.
Does any of these measurements guarantee comfort in your opinion, Dave Yates?

First off the measurements are completely irrelevant without reference to the rider, height, weight, inside leg, physical problems, riding style, purpose of bike, colour of socks etc. It may be OK for a particular person but agony to ride for another. As I have pointed out previously, how any bike is perceived by any rider is a function of their experience. Put 3 different riders on the same bike and you will get three different assesments of how it rides.
What is "comfortable" ? it is a completely subjective term and can mean all things to all people. My personal interpretation is that the bike should disapear under you as you ride it. The rider should not have to fight the bike to stay in position, which has as much to do with the set up of the bike as the material the frame is made from or whether it has a 72 or 72.5 seat angle.
There is no formula to arrive at the "perfect" bike. Personally I treat each customer as an individual with individual needs (which must be balanced against their "wants") . The design of the frame is arrived at after consultation, discussion and a bit of intuition on my part. I dont do it by numbers, a custom bike frame is too personal to rely on a computer program that tries to keep all the people happy all the time.

Cheers

Dave Yates

[Tewdric]

The discussion about steel deformation was at risk of derailing this excellent thread, so I hope no one minds me splitting it off.

http://yacf.co.uk/forum/index.php?topic=60196.msg1245454#msg1245454

[Zipperhead]

I've just noticed that my Brompton frame has a crack in it. When I put my weight on the saddle, I can't feel the crack opening at all, but I'm sure things would be different across cobbles...

You can see it here, it looks like it extends from about the seatpost clamp down to nearly the weld at the bottom of the tube. It's not quite as bad as it looks, when I looked closely at the picture, dirty water has adhered to the crack making it look a bit wider on the lower part.



So, I'm wondering if I find someone locally to weld it, whether it's likely to hold together for a few years.

[Bicycle Repair Man]

Hi Zipperhead

I would guess that is a warranty issue if you bought it new. If not it is still fixable, its steel!!. Someone fairly handy with a TIG welder should be able to fix that. You will lose a bit of paint. If you continue to ride the bike the crack will continue to grow until something eventually gives way, not tomorrow, not next week but it will go so best to get it sorted sooner rather than later.
If I were repairing this I would drill a hole at the lower end of the crack, (cant actually make out where the top is) then open the crack up a bit with an angle grinder then TIG weld it making sure I got plenty of penetration and file the top off the weld flush with the original surface. If the fillet at the joint is brass I would stop the weld ether side and re braze that bit likewise the collar at the top.

Cheers

Dave Yates

[Zipperhead]

Thanks for that Dave.

It's definately not a warranty issue - it's probably 8 or 9 years old now.

I can't make out quite how far up it goes, I may be able to see more inside when I take the plastic collar out. For now I'll retire it from use until it can be welded.

A bit of paint doesn't matter - it will be one of lifes scars, and we all get those as we go along.

[Bicycle Repair Man]

it will be one of lifes scars, and we all get those as we go along.

Got a few of those , its called "experience"

Dave Yates

[CountrySickness]

Hi Dave

I was discussing wheels with my favourite wheelbuilder last week and mentioned that I was considering disk brakes on a new custom audax bike to make it more "winterised" (and thinking ahead to LEL).  He mentioned that he's heard that steel forks and disk brakes are a bad combination and lead to a lot of snapped forks.  What is your opinion? Do Reynolds do disk-specific fork blades?

Cheers

[Bicycle Repair Man]

Hi Dave

I was discussing wheels with my favourite wheelbuilder last week and mentioned that I was considering disk brakes on a new custom audax bike to make it more "winterised" (and thinking ahead to LEL).  He mentioned that he's heard that steel forks and disk brakes are a bad combination and lead to a lot of snapped forks.  What is your opinion? Do Reynolds do disk-specific fork blades?

Cheers

None of the current Reynolds road fork blades are suitable for disc brakes. There is something in the pipeline but whether it comes to fruition remains to be seen. The forces involved are of an order of magnitude greater than for rim brakes and as your wheelbuilder says there are lots of instances of fork breakages where disc mounts have been fitted to blades that are not designed for the purpose. If you do a search on the forum you will find quite a bit of discussion on the subject. From Reynolds point of view they have to be absolutely sure that anything they do does not incur risk to the company in the form of legal action due to lack of fitness for purpose. From the framebuilders POV the same considerations apply. I have no doubt that disc brakes on road bikes will become more and more popular but I think a little more time and work is required.

Cheers

Dave Yates

[matthew]

So, I'm wondering if I find someone locally to weld it, whether it's likely to hold together for a few years.

Given where you are based and that Brompton manufacture in Brentford, could not your someone local be the original manufacturer. I don't know how long brompton warranty their frames for but I suspect they would want to see the mode of failure.