Frame 2: The First Homebuildering

[matthoult]

This spring, I attended Danielle Schon’s framebuilding course. It was fantastic!

By the time I got home, I had found and arranged for the purchase of used frame and fork jigs. Brazing supplies and tubes have now arrived and the torch should be in the mail this week. I’m on my way, but still have a good way to go.

The bike I built in class is an adventure bike. Wide drop bars, big tires, slack angles, disc brakes, etc. etc.

For Frame 2, I’m wanting to build a cross between this Bruce Gordon Monster Cross and a 61cm Tommasini Prestige I have and like a lot that was built in the 1980’s or 1990’s (SLX tubing, ~74° HT, ~72° ST, 70mm bb drop,410mm chainstays). This Bruce Gordon is also inspiration, but I’m not flexible enough to have the handlebars so far below my saddle. Thinking yellow paint as a nod to Jobst Brandt. Apparently yellow shows frame cracking and failure better than other colours.

Frame 2 Sketch/Plan:

The plan so far is a bike with 1 1/8 steerer, Columbus SL 28.6mm 8-5-8 tt, dt, and SL st, SL round chain stays and SL seat stays. Lugged BB (angles line up well) and fillet brazed. Intended to accommodate 700 x 38c. Salsa Cowbell bars in 44cm. Either canti’s or Tektro 559 rim brakes. 100/130mm axles. I’ll make the fork, too. SL blades, lugged crown. Thinking straight blade will aesthetically match the sloped TT. I’m about 6’2" and 230lbs.

Frame 1 fits me great, but it is understandably a bit stout. For Frame 2, I’m looking to make a frameset that’s achievable for me to do largely solo in my garage (rim brakes, lugged bb, some form of top cap on seat stays, etc.). I have a touring frame from 1984 made of Tange Mangaloy that has a long rear end and rides like a noodle. Its very comfortable, but isn’t a great climber. I’m not quite after a noodle, but would like to make a frameset that has a little flex to it. A very comfortable road-ish bike, with a tiny splash of wanna-go-fast sauce.

Do you think the bike I’ve sketched out above will achieve this? Any red flags or areas of concern?

Thanks in advance for your help and perspective.

[bulgie]

Are you OK with toe overlap with the F wheel? I’m OK with some, on a road racing bike for myself, but for a customer I’d need them to be pretty adamant about saying they know what they’re getting themselves into and they’re really OK with it.

Your front-center at 592 isn’t crazy-short if you use short cranks, but for me (I like 180 cranks) it would be an annoying amount of o’lap, even without fenders. (Non-issue if you’re sure you’ll never put a fender on it.)

Remember your 38 mm tires reduce toe clearance by ~ 5 mm if you’re used to 28 mm tires.

I don’t know BikeCad, does it calc toe clearance, from inputs like FC, wheel radius, shoe size and crank length? My spreadsheet does, aproximately. It says at 592 FC with a 38 mm tire, size 45 shoe and 170 cranks, expect 7 mm of o’lap. Or for me, with my 180 cranks, 17 mm o’lap, which I would not like. Still not dangerous for a rider who knows what to do, but annoying.

Your BB is a bit high for a road bike IMHO, maybe good if you plan on some garvel (or underbiking on singletrack!) With your 38 mm tires I doubt you’re planning on racing criteriums. If you’re using short cranks you can go lower. There’s no strong consensus on the effects of BB height on handling, other than a lot of people saying they like the handling better if it’s low. This may be lore, placebo and confirmation bias though. I bet most people can’t really feel the difference. But I’m one of those who drank the koolaid and likes to keep it low. I’d probably go 5 mm lower even with my 180 cranks, so you could drop it 10 easy. Maybe not if the 38 mm tires are just for ‘sometimes’, other times you wanna use 28 mm tires?

I guess with a lugged shell it might be worthwhile to let the ST-to-chainstay angle of the shell dictate your BB drop, rather than fighting with the shell to get some ideal drop number. 'Cuz like I said most people aren’t that sensitive to that parameter.

As far as your tube choices, most people would call that flexible, but not me, I’d call it about right. I’m your size, a bit heavier, not nearly the sprinter I once was so I know I can handle plenty of flex. That much ‘give’ in the frame does put more pressure on you to do everything right to minimize heat damage to the steel and avoid stress-risers, lest it fatigue crack someday down the road. Since your experience level sounds like maybe on the low end of the scale, you might want to beef up the downtube by one notch. That’s where fatigue is most likely to bite you I believe, DT at the HT joint, underneath. Or use some stronger steel like 853.

Have fun and keep us posted on the progress. Pictures please!

[guy153]

It’s a large frame, so maybe consider an 1 1/4 DT (31.8mm) to go with the 1 1/8 TT you already have. That is traditional “single oversize” sizing.

Re BB drop I built a frame with it a bit too high by mistake and it rides great. Perhaps it’s more stable because of a “tall bike” effect. Or maybe it’s just placebo and Myth and Lore (since Brandt is already in the thread But anyway, it’s now something I like.

Another benefit is that if riding in the rain it keeps your feet a little bit more out of the splashes. The downsides are standover and ease of getting on and off, which are non-issues for an experienced rider, but I always try to get the BB nice and low for novice riders.

[Duanedr]

I prefer a bit lower BB and longer stays for a bike this big. lowering the BB would also give a few more mm of toe clearance. BikeCAD does calc toe clearance based on shoe size, cleat position, crank length etc. etc.

[manzanitacycles]

Right now your bike is really short front to back and tall up and down. I would increase the wheelbase and lower your position. I personally hate toe overlap, but you may not care. I’ve also ridden bikes that were too noodly for me (5’10" 165lbs) and grew to dislike them. Also, if you’re acquiring a frame jig, there’s no reason you need to be confined to a lugged BB shell.

Here’s what I would change if it was going to be my bike:

• longer front center to reduce/avoid massive toe overlap
• 270mm BB height (assuming 175mm crank arms)
• 72º HTA with 50mm fork offset to help with toe overlap, add some wheelbase, and increase trail with what appears to be a very rear wheel heavy weight distribution
• 31.8 9/6/9 DT
• lugless BB shell
• 435mm CSL to move more weight to the front wheel

Feel free to ignore all of my suggestions though. Only you will be riding this bike.

[matthoult]

Thank you for the great reply!

Toe Overlap - I really don’t like it. While the paid version of BikeCAD does have toe overlap features, the free version I’ve used here does not. I’m typically a fan of shorter cranks – 160 or 165mm – but have a 172.5 set from a used Record group I was planning to use with this frame. I measured on my Tommasini with its 170mm cranks. It is tight, but does not have toe overlap. That table sounds very handy. If I need to, I was planning to adjust the HT angle from 73.5° to 73° or 72.5° or increase rake, if I need to. A decade + ago, I used to ride 32c tires. I’m older now and don’t ride like I used to. A little extra ‘suspension’ is appealing.

BB height/Lugged Shell – This is a personal preference. I tend to prefer frames with 72° seat tube angles and high-ish bottom brackets–60 to 65mm drop. I have a couple of bikes with 70mm drop–the Tommasini with 28c tires and the other is a monster cross frame running 43c - 50c tires. For this frame, I’d like somewhere between 65 and 70mm of drop. I like your idea of giving the lug what it needs to work.

Tubing Choice – thank you for validating/confirming my tubing choices. Also for the downtube advice. My experience level is indeed on the low end of the scale.

Thanks! Pictures and progress will come, if slowly

[matthoult]

Thanks! I anticipate I will use most of the length of the Sl stays. They only seem to come in 410mm length.

Do you know how to check toe overlap in the free version of BikeCAD, or is it a feature on the paid version only?

[matthoult]

Thank you, manzanitacycles.
I was planning to use the lugged bb is for a couple reasons. On a different thread, someone explained that the lugged bb was very handy for adjusting navigating tolerances and cutting the chainstays to fit. I really enjoyed using a milling machine to make Frame 1. I won’t likely have access to one for Frame 2. Filing bb fillets isn’t as much fun as other parts of frame building I’ve experienced so far.
If I can get another 5mm out of the chain stays, I think I will

[manzanitacycles]

@matthoult

Do you know how to check toe overlap in the free version of BikeCAD, or is it a feature on the paid version only?

You can do some math to approximate it:

Front center - crank length - toe to center of cleat length - wheel radius

If the total is -20 or below you’ll likely have some toe overlap.

[Duanedr]

I don’t know about the free vs paid features. I just quickly mocked this up with the following:
Crank: 172.5
Shoe Size: 11

Notice, my drawing has an extra 5mm in clearance than yours (probably fork offset difference) so, you’ll have some significant overlap. I’d relax the headtube to 72.5*. You won’t really notice after a ride or two.

[bushtrucker]

As others have said, I would avoid toe overlap if possible. One of those things that really pisses me off.

First option is to slacken the front end and increase fork offset. HTA depends what fork is being used and how much rack/offset it has but you should have no issue getting down to 72°. Add a dimension for trail so you can see how that changes.

You could also lengthen the top tube. Do you plan to ride a lot in a group or mostly solo? Trad road frames use a short top tube and long stem to get the rider as far over the front wheel as possible. Their ideal position is as close to the rider in front of them a possible for maximum aerodynamics. Hot take coming Stability is compromised because of this but professional riders are willing to make that trade off. And casual riders are so used to this position that if feels normal.

In my experience a bike with a slightly longer front end will rider better/smoother. I’ve ran stems as short as 60mm with drop bars and which is about as short as you can go while retaining some kinda classic aesthetic. If you’re currently using a 100mm stem then that’s 40mm of top tube to be had! If ya happy to get ya freak on stem wise then you could try and even longer than that.

Also while figuring out the frame design you should mostly focus on fit numbers. Add dimensions to contact points like @Duanedr has. These are what you want to keep constant while playing around with everything else.

[Hananas]

Totally agree on the stem length thing.
I personally much prefer a longer frame with a shorter stem over the traditional giraffe neck setup. I’ve also happily gone down to 60mm and personally think the sweet spot is around 70-80mm for me. (I’m 1.83m aka 6’)

[bushtrucker]

Oh and forgot to mention that any added length to the wheelbase means you can get away with a slightly higher BB without compromising too much in stability. For me (on 175mm cranks) the minimum BB height I want for road/all-road is 290mm. For ATB/off-road it’s 310mm and for MTB it’s 330mm. That’s pretty terrain dependent though as things are rough around here. Keen to see where you land on it all!

[matthoult]

Thanks for this perspective. I’m used to 110 or 120mm stems being the norm. It’s good to have things taken for granted challenged.

[matthoult]

Re: downtube, I had planned on using an SL tube in 8-5-8. Looking at beefing up the downtube by a notch, I took a look at 853, but didn’t see it in 9-6-9 in 28.6mm from the supplier I found. However, I did find an SLX downtube in 9-6-9, which seemed like a good match for the rest of the SL tubes being used for the frame, so it is now on order.

[guy153]

I would consider 31.8 for the DT anyway if you want to beef it up. Add wall thickness for strength, diameter for stiffness. Any bike tube you can buy will be strong enough unless you ride like Sam Pilgrim or Fabio Wibmer.

[matthoult]

Some pictures from work so far. I forgot to take pictures before wrapping up for the evening, but most of it’s here. Figment is much better than is shown in these pictures.

The front triangle has its bilaminates in place and is ready to start brazing together.

[matthoult]

Good progress on the fork, too.

Crown and steer tube are brazed together. Again, these photos are a little behind. All the other pieces are ready to go as well. The pause now is for either finding an LBS with a crown race cutting tool, buying my own, or finding access to a lathe that can accommodate the inch and an eighth steer tube. It always makes me nervous when I see videos of the forks flailing around. Just the crown, less so.

[bulgie]

@matthoult

[…] or finding access to a lathe that can accommodate the inch and an eighth steer tube. It always makes me nervous when I see videos of the forks flailing around. Just the crown, less so.

I wouldn’t worry about it. In my experience, any lathe with a spindle bore big enough for the steerer is heavy enough to handle to off-center weight spinning.

Lots of crowns have so much metal there, that the hand-turned crown-race cutter is a poor choice. Too much work, too much wear on the cutter, plus all those extra revolutions it takes are likely to result in an undersized seat. IMHO, those hand tools should be reserved for lighter cuts. The lathe is the correct tool.

[matthoult]

I’m overdue for an update.

The front triangle went together okay. I have a Doug Fattic frame jig. I’m sure its dandy, but I learned on an Anvil, so I’ve struggled a bit with it.
The downtube slid a little when I tacked it to the headtube, so it isn’t as perfect a joint as would be ideal. If I could do it again, I would have put a clothespin-style metal clamp in place to better keep things in place.