Rotrax build

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Rotrax build

Postby RobertFrith » Sat Dec 31, 2011 10:08 am

So I arranged my own Christmas present this year. Worked out well; I bought an old Rotrax frame from silverlight.
I intend to use it which means furnishing it with seat, seatpost, wheels, crankset, BB spindle, brake, stem and bars. I could use some help.

I'm not too fussed about being period correct (I can't be - it doesn't have drillings for brakes, I won't be adding them but I'd like to be able to stop it reliably!). I would like it to look the part as much as possible though.

Seatpost
The top of the seat tube is a little out of round. with the calipers at 90° to the frame I get 26.8mm, at other points round the circle I can get measurements as low as 26.1mm. Looking at the clamp it seems to me it should be a little wider, do you reckon it's safe to assume I need a 26.8mm seatpost?
Also, the distance across the clamp is around 17mm, what length seatpost bolt should I order?

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Crankset and BB spindle
I'm inclined to go cottered and have already bought a cheap 46t set off eBay. The frame has BB cups but no spindle. Spindles are available, Moruya have new ones here. I'm not sure which one I need to get the correct chainline though.

Wheels
Frame is 110mm. I'd really rather not have the rear stays reset but it does limit the rear hub options. BMX and Keirin hubs are readily available. I'm thinking of running a modern SA roller brake hub up front (I think this is the one Pashley use on the Guvnor). I could pair it with SA's 2 speed kick shift coaster brake hub at the back, it has a 116mm OLD but I reckon that'd be OK to squeeze in without resetting the rear forks (1.4kg though!)
Is there anything else I should be looking at?
Rim suggestions welcome, obvioulsy won't need braking surfaces.

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by BNA » Sat Dec 31, 2011 10:14 am

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Re: Rotrax build

Postby RobertFrith » Sat Dec 31, 2011 10:14 am

Oops, I have one more question... what's the best way to attach the aluminium headbadge?
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Re: Rotrax build

Postby rkelsen » Sat Dec 31, 2011 12:35 pm

Nice pickup. Congrats! :)

I'd go for a 26.8 mm post, and try to gently prise open the clamp a bit, by using a screwdriver as a lever in the bolt holes. Just a tiny bit for each side.

The badge can be stuck on with double sided car badge tape from Supercheap Auto.

With respect to the cranks: Are you sure you want to go cottered? If you're going to ride this bike, you'll end up kicking yourself later. Personally, I'd go cotterless.
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Re: Rotrax build

Postby RobertFrith » Sat Dec 31, 2011 1:33 pm

rkelsen wrote:With respect to the cranks: Are you sure you want to go cottered? If you're going to ride this bike, you'll end up kicking yourself later. Personally, I'd go cotterless.

What are the issues? I do remember constantly barking my ankles on cotter pins many years ago, are there other problems? If I went cotterless what would you suggest for something like this?
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Re: Rotrax build

Postby spirito » Sat Dec 31, 2011 2:48 pm

rkelsen wrote: Personally, I'd go cotterless.


Me too. Life's too short to go messing with cotter pins, and without having a good cotter pin press it makes it all much harder. Makes maintenance a pain in the ass.

You can still use your 5 pin chainring with cotterless cranks. Stronglight 49d is more of less the original and the best, going strong since the 1930's. Heck, if nobody else need now I'd use a cartridge BB as I've done here. 113mm JIS taper Symmetrical gave me a good chainline here (ymmv).

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I'd also steer clear of the Sturmey 2 speed kick hub. Lots of play, drag and poor quality ime. I've not liked anything Sturmey have made recently. Doesn't deserve to carry the hallowed name.

Rotrax !!!! Great marque, well bought 8) :wink:
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Re: Rotrax build

Postby rkelsen » Sat Dec 31, 2011 5:23 pm

RobertFrith wrote:What are the issues? I do remember constantly barking my ankles on cotter pins many years ago, are there other problems?

Weight: Cottered cranks have to be made from hardened steel due to the way they interface with the spindle, so they're Very Heavy.

Disassembly: The spindle and cranks are made from hardened steel. The pins are made from a milder grade of steel. This means that over time/with use, the pins will deform. It doesn't matter whether you install them correctly or not, this will happen unless you regularly disassemble them. Deformed pins will make you swear excessively when you try to remove them, so make sure the kids aren't around when you do it. If you don't have a cotter pin press, as mentioned by Spirito above, then you will have to use a hammer & punch. In my opinion, that frame is far too nice to meet with a hammer that closely.

Appearance: Yes, it's highly subjective, but I think cotterless cranks look far neater.

Cotterless spindles are readily available (in more than the 3 sizes in the link you posted), so there's more of a chance that you'll be able to get the right chainline.

Also, as mentioned by Spirito, you can use a cartridge BB and nobody will be able to tell. With cotters, there is no such thing.

There are many, many variations in cotterless cranks available. Some of them are more period correct for your frame than others. The Stronglight 49d is the perfect example of something that would suit.
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Re: Rotrax build

Postby WyvernRH » Mon Jan 02, 2012 7:57 pm

Nice buy!
Me, I'd forget about a front brake and go for the Sachs two-speed kick back coaster brake hub at the back. I had one of these on a Moulton a while back and it worked really well.
Very minimalist, no cables and you can pretend you are one of the'Suicide Squad' riding a (very high class) fixie with no brakes :wink:
Or.. maybe fit a Fichtel 3 speed coaster hub, only one cable?
Cheers
Richard
PS if I had known there was a Rotrax for sale in Oz (specially one that nice) you would have been left in my dust! :)
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Re: Rotrax build

Postby Clydesdale Scot » Mon Jan 02, 2012 8:32 pm

RobertFrith wrote:Oops, I have one more question... what's the best way to attach the aluminium headbadge?

or you could use split (bifurcated) rivets as was suggested for this restoration

[edit] or another suggestion is hammer drive screws from specialist fastener suppliers, or model supply shops.
Last edited by Clydesdale Scot on Mon Jan 02, 2012 8:56 pm, edited 1 time in total.
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Re: Rotrax build

Postby Stuey » Mon Jan 02, 2012 8:37 pm

I'd make up some fake rivet heads and fit them to the badge holes, THEN stick it on with double sided tape. Unless you have to leave it somewhere where the badge can be removed easily.
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Re: Rotrax build

Postby Velo13 » Mon Jan 02, 2012 9:46 pm

Stuey wrote:I'd make up some fake rivet heads and fit them to the badge holes, THEN stick it on with double sided tape. Unless you have to leave it somewhere where the badge can be removed easily.


Yeah, I've always used "exterior" grade double sided tape - stick several strips to badge, cut around edges so it's all neat, and then stick on the frame. Sweet!
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Re: Rotrax build

Postby RobertFrith » Tue Jan 03, 2012 11:11 am

I do have a cotter pin press, but I hear you on the other cotter issues. I'm watching a couple of 49d's on fleabay.

Vintage two speed hubs seem to have a bit of the proverbial hen's tooth about them. It's looking easier to turn up a pair of period correct harden/airlite hubs than a sachs or bendix 2 speed kickback. I like brakes at both ends, bit old fashioned I know, I can live without the extra gear though, so maybe vintage coaster brake at rear??

Thanks for the head badge ideas. I like the bifurcated rivet idea; would make for easier removal should it ever be required.

Frames are still built under the Rotrax name and they sell new stickers and badges (and rivets). Looking at the discussion on their contact page it seems they may be able to advise what running gear the bike was originally fitted with - will drop them a line.
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Re: Rotrax build

Postby WyvernRH » Tue Jan 03, 2012 11:17 am

RobertFrith wrote:Oops, I have one more question... what's the best way to attach the aluminium headbadge?


You could use very small alloy pop-rivets? I've used these in a couple of re-builds and while not 'period' they are effective and look neat.

Cheers
Richard
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Re: Rotrax build

Postby Stuey » Tue Jan 03, 2012 11:23 am

I only mentioned 'fake rivets' if you went down the route of double sided tape. As the holes are in the frame, I'd just use rivets. Chromed brass bifurcated ones sound like the go. I have some, but unfortunately they're just raw carbon steel. Easy enough to get though, and you could turn over the ends easily enough through the headtube. Good idea!
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Re: Rotrax build

Postby WyvernRH » Wed Jan 04, 2012 8:23 am

Another brake option you could use is to look out for some old Resilion clamp-on cantilevers (with front mounts that fit round forks). Very effective and totally period, if a little unsightly to modern eyes. (I'll dig out a picture and edit it in later).
Or, I believe you can get a modern version of the Resilion which clamps to the forks, made to fit track bikes with no drillings. These turn up on e-bay from time to time but again, there may not fit the round forks.

Cheers
Richard
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Re: Rotrax build

Postby silverlight » Wed Jan 04, 2012 1:19 pm

Im glad your happy with the Rotrax.
It really is a wonderful frame and built up will look great.
Rotrax are regarded as really top end builds, as you can see their lug work is really nice, while other makers were at times overdone Rotrax were pleasing to the eye and finely Sculptured. Detail throughout the frame is amazing and the forks look great.
This frame would have been a dedicated track frame, no mudguard eyelets for path or road setups etc.
From memory Rotrax also built the later Thanet Silverlights, extrodinary bikes (one of my other projects) so they were very respected in their day and to remain today is a great achievement.
Great that there is a connection of its birthplace with a family member which makes it extra special.
I look forward to with your progression of this fine cycle.

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Re: Rotrax build

Postby RobertFrith » Thu Jan 05, 2012 8:59 am

this from Tim Maund at Rotrax; "Thankyou for your enquiry regarding one of our Rotrax "Vel de Hiv" we built in 1956 and from the last three numbers would indicate it as being approximately July.... The build spec would be Gunutti headset, GB stem & bars, cottered bottom bracket and single ring chainset, either Williams or Chater Lea. Hubs - large flange British Hub Company and rims Fiamme"
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Re: Rotrax build

Postby WyvernRH » Thu Jan 05, 2012 8:10 pm

RobertFrith wrote:Seatpost
The top of the seat tube is a little out of round. with the calipers at 90° to the frame I get 26.8mm, at other points round the circle I can get measurements as low as 26.1mm. Looking at the clamp it seems to me it should be a little wider, do you reckon it's safe to assume I need a 26.8mm seatpost?


Sorry meant to post this earlier. What you need is a set of internal calipers or an internal micrometer. Use the tool to measure the diameter of the seat tube about 50mm down from the top, this should get you clear of any distortion that has accrued over the years and give you a true diameter measurement.
Cheers
Richard
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Re: Rotrax build

Postby RobertFrith » Thu Jan 05, 2012 10:16 pm

Thanks Richard,
I've taken a punt and ordered a 26.8 post from Moruya. I have my fingers crossed
Rob
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Re: Rotrax build

Postby RobertFrith » Fri Jan 27, 2012 12:07 am

Update;
26.8 seatpost arrived and installed, no slop but not as tight a fit as my other bikes. A 27.2 definitely won't fit though.

I also picked up a few bits and bobs off fleabay;
• nicely patined Brooks B17, pic below
• Harden Bacon Slicer hubbed front wheel, pic below
• Stronglight 49D crankset with 46t chainring, in transit
• GB alloy headstem, in transit (still got my eye on a nice steel "spearpoint" one though)
• Lyotard pedals (probably from the 70's but they have a great retro look, think they're the 460..), in transit

Some Resilon brakes came up on e bay but they look a bit knackered so I'm passing on them. I'm not sure I'm keen on fussing up the front end of the bike just to stay period correct. I'd still like to be able to stop so I think I'm going to stump up 20 quid for a single speed coaster brake hub from Bikefix. I can cope with the visual fuss of the actuator arm under the left chainstay for stoppage. They stock a 110 OLD unit too - sweet!

Decisions left to be made are;
Rims.
Reading another thread on BNA I'm inclined to the Velocity Razor 700s or the H+Son Tb14. I came across these as well, Grand Bois Rims, anyone know good or evil about them??
The Harden hub came laced to a Mavic MA40 which is pretty enough but it's black and I'm not sure that suits. Anyway I'd have to find another to match for the rear wheel and since it's neither period correct or the right colour I reckon it might be easier to buy two modern rims that at least look the part.
Handlebars
According to Rotrax it would have originally had GB bars. I've watched a few bars come and go on e bay. I think they're going for silly money until I look at what a Nitto track bar sells for new. The fact that I'm not really sure what I'm after is compounded by the difficulty of understanding what's being offered by online sellers. It would be good to be able to handle bars prior to purchase. Suggestions welcome!
Bottom bracket
Too much guesswork involved in establishing chainline so I think this will have to wait until I have a back wheel installed in the frame.

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Re: Rotrax build

Postby spirito » Fri Jan 27, 2012 8:40 am

RobertFrith wrote:

Decisions left to be made are;
Rims.
I'm inclined to the Velocity Razor 700s or the H+Son Tb14. I came across these as well, Grand Bois Rims, anyone know good or evil about them??


I'm a fan of Razor's (well priced, available through lbs etc). Many good things written about the H+Son Tb14 but remember they're 23mm wide so you'll have to use a tyre at least that width. Grand Bois rims are nice, classic looking and I've built up 2 sets. I think the Razor is a better rim, but the Grand Bois looks very traditional.

They're all good options but the rear spoke hole count will be the deciding factor. Traditionally, your Rotrax would have had a 32h front wheel and 40h rear, none of these rims will have a 40h rim option. Some may not be available in 36h. See what spkme hole options there are and what you plan to use.

RobertFrith wrote:Handlebars
It would be good to be able to handle bars prior to purchase. Suggestions welcome!


I agree. So many people are happy to sell stuff that would be better suited for the garbage bin. I'm very cautious with 50+ year old Aluminium handlebars, especially as many are heavily gouged or scratched. Too cheap a bar means you pay later at the dentist.


Bottom bracket

RobertFrith wrote:Too much guesswork involved in establishing chainline so I think this will have to wait until I have a back wheel installed in the frame.


It's not too hard and is easy to trial fit. The last 49d I had worked well with a 113mm JIS tapered shimano bottom bracket. It was Symmetrical and gave a good Chainline with a 115mm spaced rear hub. Your mileage will vary depending on how the taper is and what rear hub you're using but it's not too hard. Let your rear wheel dictate the chainline and you can play with different BB options to have it running straight and true.

I know some will poo-poo at me suggesting a sealed cartridge BB but you'd have to look very hard to spot it and makes things pretty easy to source or get right.
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Re: Rotrax build

Postby Clydesdale Scot » Sun Feb 05, 2012 7:38 am

and addendum to the discussion on how to reattach the badge
there has been some recent discussion on BikeForums on this.
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Re: Rotrax build

Postby RobertFrith » Sat Mar 24, 2012 11:10 pm

update and question;

I've been getting bits together as one does. Since my last update I've bought two rear hubs; a bacon slicer (28h) to match the front and the modern coaster brake hub from Bikefix (36h), modern half drop Charge Cool bars. I missed the GB spearpoint stem I bid on on eBay but bought another direct from the seller (who is also restoring a Rotrax frame).

I need to either build or have built a wheelset and sort a BB. I've never built a wheel and would be quite happy to have someone else handle it but I'm a bit cost sensitive at the moment :!: Plus the idea of building a wheelset is appealing. Dismantle in Freo have the kit so I wouldn't have to outlay on tools and they say they'll run a course in the next few months. Not sure if I can wait that long though....

My question is do bottom brackets ship with bolts? The Stronglight crankset I bought didn't - didn't really occur to me when I bought it :oops:
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Re: Rotrax build

Postby Stuey » Sat Mar 24, 2012 11:17 pm

RobertFrith wrote:I need to either build or have built a wheelset and sort a BB. I've never built a wheel and would be quite happy to have someone else handle it but I'm a bit cost sensitive at the moment :!: Plus the idea of building a wheelset is appealing. Dismantle in Freo have the kit so I wouldn't have to outlay on tools and they say they'll run a course in the next few months. Not sure if I can wait that long though....


Robert, I built two wheels just using the instructions and colour coded diagrams given by Sheldon Brown and it was quite easy, but time consuming.
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Re: Rotrax build

Postby RobertFrith » Sun Jun 17, 2012 11:39 pm

I haven't been completely idle on the Rotrax!

For better or worse I'm keen to extend myself and build some wheels. I've just this evening finished building a Musson pattern truing stand. Hubs I have (as discussed earlier I need some braking. I ended up buying a new coaster brake hub from Bikefix in the UK. I also have the Hardens I mentioned earlier in this thread.) I need rims, but I wouldn't mind getting a bit more detail from you lot if you can help.

I was sold on the Velocity Razors... two questions though; is the profile the same as the Synergy? - looks to be on the Velocity site. If it is I'm not sure the squarish shoulders are right for me (I'm familiar with the Synergys as I have them on my commuter/tractor). What is the finish?

I'm looking harder at the H Plus Son TB14s. The profile looks better, they sell direct and they're available in a high polish finish.

Thanks
Rob
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Re: Rotrax build

Postby Clydesdale Scot » Mon Jun 18, 2012 7:13 am

just to confuse things for you, but have you considered these?
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they are on a e bay now item no. 110898830472
just need to negotiate a sale outside of the UK.
Perhaps those more experienced might comment on how effective they were.
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