P-38 build

DIscuss anything relating to non-standard cycles and their equipment.
Blondie
Posts: 239
Joined: 23 May 2021, 5:11pm

Re: P-38 build

Post by Blondie »

UpWrong wrote: 17 Jul 2021, 8:45pm Nobrakes, that's an interesting analysis of the effect of a couple of kilos of weight. I think I said up-thread that my hope with the P-38 is that I'll be able to climb better with it than on my existing 'bents.

I've finished building the front wheel: Deore hub, CR18 rim, 32 spokes, PG, 2x, weight 800g without QR. I was surprised that it's 340g lighter than the rear wheel even with a heavier hub, rim construction and spoke construction.
No cassette, much smaller rim and tyres etc. Cassette alone is 300-400g of a rear wheel
UpWrong
Posts: 2401
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

It just dawned on me that most of the difference between the weight of the rear wheel and the front wheel is the freehub. Also a 622 mm rim is about 50% longer than a 406 mm rim, so I really should not have been surprised. I have yet to install a cassette.

I'm currently trying to clear an area inside the house so I can put the bike together. It's a bit difficult when much of the junk inside the house is not mine :roll:
belgiangoth
Posts: 1657
Joined: 29 Mar 2007, 4:10pm

Re: P-38 build

Post by belgiangoth »

You need to buy a gazebo and build it in the garden
If I had a baby elephant, I would put it on a recumbent trike so that it would become invisible.
UpWrong
Posts: 2401
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

After 3 days work and hard negotiation I have cleared enough space to do the build :lol: . I need to work out how to install the carbon fork (with carbon steerer). There must be a way to pre-load the bearings. It's not covered in the rather spartan assembly guide.

Have been pondering my gearing options. I want to keep it as light as possible whilst providing very low gears and short cranks. I have an SRAM pg990 which I'm keen to use although the 17-20 gap is likely to annoy me. I have some 24/33/44 rings which will fit the XD-2 cranks, and a titanium BB to put the cranks on. Sheldon Brown's calc says that will give 19.2" to 108.7" depending on what tyre I squeeze in. Excited :mrgreen:

In terms of cassette weights: PG990 11-34 is 304g, whereas an Aivio HG400 12-36 is 413g. The 12-36 has nicer ratios and would give a lower range of gears: 18.1" to 99.6". Guess if I fit the Deore shadow RD then it will be straightforward to swap to the lower range if needed.
UpWrong
Posts: 2401
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

The headset adjuster is described in the Phantom manual. It's a neat solution and depends on an adjuster ring pressing down on a combined dustcap/compression ring to preload the bearings. The problem was there appeared to be a mismatch between the dustcap/compression ring and the top cartridge bearing so that it didn't function properly either as a compression ring or as a dustcap.

I had a compression ring in my spares box which matched the bearing. So far so good. I didn't however have a dustcap which pressed down on the bearing and covered the top bearing cap. So I've retained the dustcap/compression ring as a dustcap which pushes down nicely on the compression ring I installed but there's a gap between it and the top bearing cup so rainwater is going to get in. I'll try to upload some photos.
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UpWrong
Posts: 2401
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

Sorted. I had the dustcap upside down. I think the frameset came with the compression ring missing. It definitely needs the one I have installed. The dustcap is just a dustcap with a seal round the rim. I had it upside down thinking it had to be that way to bear down on the compression ring, but it feels like it was able to apply the pre-load ok the other way round. Will find out for sure when I ride it of course.
UpWrong
Posts: 2401
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

Seat on, some North Road Style handlebars on, boom in. Weight is a touch over 12lbs. I don't think the handle bars are going to work. I need to get the wheels on then I might be able to judge better.
UpWrong
Posts: 2401
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

Wheels are shod and ready to go on. I bought some new handllebars which look perfect for the P-38 and will allow me to fit rapid-fire shifters and use normal V-brake levers. They are tweener style with a 15mm rise so can be flipped to adjust for reach. And they are aluminium. And they are black. Very happy :mrgreen: . Pictures to follow shortly.
seldomseen
Posts: 21
Joined: 22 Jul 2014, 10:20am

Re: P-38 build

Post by seldomseen »

Would love to see the bars and to know where you got them from!
UpWrong
Posts: 2401
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

The bars are Humpert Toulouse, 560mm wide at the widest point. There are several stockists in the UK.
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n0ct0
Posts: 63
Joined: 27 Apr 2020, 2:11pm

Re: P-38 build

Post by n0ct0 »

Looking good. Awaiting the first ride report!
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[XAP]Bob
Posts: 19793
Joined: 26 Sep 2008, 4:12pm

Re: P-38 build

Post by [XAP]Bob »

Looks like it’s in a fit state for a roll down test
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
UpWrong
Posts: 2401
Joined: 31 May 2009, 12:16pm
Location: Portsmouth, Hampshire

Re: P-38 build

Post by UpWrong »

Houston, we have a problem. I couldn't get my leg over :shock: . The step over is high for me and the steering riser is fixed. The longer handles of the bars don't help and rather get in the way. With help I managed to get on it. I found I could only get my toes on the floor. The bars seemed a bit close. What to do? I can tinker with the bars. It would help to get some brakes on it so I can hold it steady when mounting/dismounting. I would like to keep the 406/622 wheels rather than drop to 349/559.

Have to say, most new bikes are awkward at first, so getting the brakes on it and trying alternative bar configurations to make cockpit space for getting on and getting off makes sense.
Blondie
Posts: 239
Joined: 23 May 2021, 5:11pm

Re: P-38 build

Post by Blondie »

What tyre do you have on the front? I run a Pasela 37mm
seldomseen
Posts: 21
Joined: 22 Jul 2014, 10:20am

Re: P-38 build

Post by seldomseen »

Never checked out Humpert handlebars before, but they do loads of different styles - all sadly not long enough for what i need, and really cheap too. Thanks to Brexit no one in europe will ship to the uk, so had to get some from Taiwan!
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