In order to build a custom built frame, it is necessary to first determine the position that the finished bicycle is going to be set to. This done using our frame fitting jig and years of experience to determine an efficient and comfortable position.
Once the position has been determined then it is possible to work out some provisional frame dimensions that will allow this position to be set up on the finished bicycle, these will be fine tuned by our frame builder when he draws the scale drawing prior to building the frame.
Effects of the position on the frame design.
When drawing out the working drawing, the position is marked on the drawing first, the amount of exposed seat post along with the type of saddle will determine length of the seat tube. The type of seat post (ie. amount of set back), type of saddle and where you would like the saddle to be positioned on the seat post will then determine the seat angle.
The stem length you require can be drawn in next and this along with the stem angle, amount of spacers required underneath, the stem, and the type of headset will then determine the top tube length and the height of the head tube required to set the bar drop and reach. The only other requirement affecting the basic frame design is whether top tube is preferred to be level or sloping, if the top tube is required to be level then it becomes more difficult keeping everything else in proportion, as whatever height the head tube ends up being pre-determines the height of the top of the seat tube as this will be at the same height. This could then mean that the amount of exposed seat post will be less than desired., this can adjusted slightly with a little unnoticeable amount of slope gaining a centimetre or so and/or a head tube extension, after this it is a matter of less seat post exposed and fewer headset spacers or more seat post exposed and more headset spacers.
Other items that can be specified on a Hewitt Custom built frame.
Once the main triangle dimensions have been determined, there are quite a number of other decisions to be made, such as the type of tubing, whether the joints are going to be lugged, fillet brazed or TIG welded.
Brazed with Lugs
This is the more traditional method of building a bicycle frame, using this method the tubes are joined with external lugs the tubes are then brazed into the lugs to secure them. This system has a very traditional appearance to it partly due to the lugs themselves, but also because the lugs restrict the diameter of the tubes to reasonably narrow diameters and the angles of the tubes are also restricted to the top tube being pretty much level.
TIG Welding
TIG welding is currently gaining popularity for the following reasons, it is generally the method that most of the newer frame tubes are designed to suit, essentially shorter thicker butting, without lugs the angles and diameters of the tubes are less restricted.
The general style of the frame will maybe then determine a number of other details, such as the chain-stay length, handling characteristics, rear drop out width and brake and tyre clearances.
This the leaves the brazed on items required and where they are fitted, it is also and the finish to be decided on.
Please click on your desired frame below for more details.
Race frames
Hewitt Fiera
Hewitt Fiera S
Hewitt Fiera CS
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