Sharratt is Go!

prot4

The first prototype of the fully New Zealand designed and manufactured Sharratt bike is completed and on its way to Eurobike to take the mountain bike world by storm. We asked its creator Craig Sharratt the ins and outs, hows, whats and whys of his Kiwi take on the ultimate mountain bike.

The obvious question; why? Because we feel we can add something new to the market that offers unique points of difference. There is no better bike than one that is built for an individual rider. In manufacturing a full suspension frame it is difficult to balance custom options around a suspension system and within a realistic cost. I think we can do this because of our combination of knowledge and equipment. The Sharratt Prototype One, once in production, will be available in the three wheel sizes, 26, 27.5 and 29 with geometry options for each. This will mean we can make a broad offering of tailor-made bikes based around one platform.

Did you take inspiration from the Zerode project or was this something you had already been planning? My main inspiration to design a frame goes back to when I first started mountain biking in 1990 and came from the leading brands at the time. About 2002 I started gradually purchasing machinery and frame building equipment to put together quite a good workshop including the very best frame jig and tube mitring tooling I could find, importing these from the States. I have built steel frames before, the first about eight years ago. Any New Zealand made brand is awesome to see and I admire Zerode for getting their frame into production; that is our goal too. Any timing however, is coincidental. Design work for the Sharratt frame started December last year, and was planned as it seemed the right time for our business.

How much is this costing? The main cost so far has been time. Without discussing exact dollars, I would say we are quite happy at the point we are at for the amount that has been spent.

Will all production bikes be made in New Zealand?  And by whom? Yes, the plan is to build the Sharratt frames in Christchurch because we want to offer custom geometry. The frames will be built in batches every 4-8 weeks depending on demand, and fabrication will be done in our own workshop including tube mitring, welding and bonding. We are extensively utilising CNC machined parts and for these we have built a good relationship with a precision engineering company in Asia. The entire rear triangle parts including seat and chainstays are machined from solid billet and internally incorporate multiple reinforcing ribs with carbon fibre plates bonded in place on the top surfaces. While very expensive, the parts are light and incredibly stiff. Parts used for the pivot locations are mechanically locked and bonded in place as we want to eliminate as many welded areas as possible. The combination of machining, bonding and minimal welds means we can make a frame to very precise alignment tolerances making the wheels track straighter, the suspension work smoother and bearings last longer.

In designing the bike I wanted to have some connection to the boom era of mountain biking which was the early 1990s. At this time the so-called cottage industry in the USA was pushing the development of equipment with CNC machined parts because it allowed the smaller companies to produce very high-tech designs. Hope in the UK has built a very successful brand using CNC machining as their production method. The Sharratt frame is my take on an historical period in mountain biking but in a modern design for today’s rider and today’s trails.

Is that cost prohibitive? If we were to sell the frames through distributors or shops then it would be impossible to manufacture using the methods we want to utilise and have it made in New Zealand. With our company BikeCycle we offer products directly to the end consumer and because of this we will translate what we have done and learnt there to the Sharratt frame. The goal was to design a frame without compromise and then offer it direct to the rider to keep it within what will be an amazingly competitive price. As an example, with the amount of machining we have in this frame, if we sold to a distributor, they to a shop, then the shop to the end user, this would have to be a $5000 frame. As it is we are on target for this to be a frame built to incredibly high standards with contruction methods that no one else is using and have a selling price of $2500 including shock, with complete bikes with a Sram X7 or Shimano SLX build for somewhere in the low $4000 range.

How many bikes will be made? We intend to manufacture frames in batches for the reason that we can offer more options to the rider this way than doing large production runs. Sharratt frames will be made to order so the intended maximum wait will be eight weeks for a frame that will be custom made for the rider. If an order is received a week before a scheduled batch then the delivery time to the customer may be only two weeks. Our tooling is set up to allow geometry changes without adding much time to the production process. We may keep in stock later on some popular frame option combinations in a raw finish ready to paint.

Run us through the numbers; geometry, travel, etc… Keep in mind that we are at frame one and the design is going to change to some degree as we apply what we have already learnt with Proto One. We are intending the headtube angle, top tube length, and maybe bottom bracket height and chainstay length to be customer selected. There are some limits to this as the suspension will be affected by the bottom bracket height and chainstay variations. The options here will only be +/- 5mm in either direction, still enough to tune the weight distribution of the rider on the bike though. If we talk specific about this actual bike, which is designed as a Medium size, to give an idea of what we think is bang in the middle of what people want, the numbers for that are: Head Angle 67, Seat Angle 74, Top Tube 610mm, Bottom Bracket Drop=0mm, Chainstay 428mm, Wheelbase 1167mm. Travel is 150mm on this bike but this will probably go out to 160mm on the 26 inch-wheeled production frame. We are working on the designs for 650b and 29 inch frames also but the 650b will definitely be 150mm travel and the 29 will be 130mm. Missing from the Proto One frame is the seat tube/top tube gusset, the aluminium billet we needed to make one was not yet available at the time of making this frame.

Can you explain the suspension, how it works and why you went that route… Essentially the frame is a single pivot with a relatively vertical wheel path. I did this to minimise centre of gravity changes of the rider’s body weight and also to keep the rate of chain growth consistent. I think a shock is more tuneable with this type of design so it gives the rider more freedom to adjust the bike to suit them. The shock stroke is 57mm but this will be increased if we do go to 160mm travel. The shock rate does not vary much throughout the stroke, I have aimed for a linear rate and with the right shock the rider can tune the characteristics of the suspension to a certain degree from there, hence why we fitted the Proto One with a RockShox Monarch Plus RC3. I’d rather not talk about other details of the suspension mechanics just yet as this may change before production but would note the main pivot location is placed to work best with double chainring setups.

A lot of riders get hung up on the theory of suspension design without taking into consideration that the biggest influences on how a bike rides is where the rider's weight is distributed in relation to the wheels, and how they apply torque throughout the pedal stroke. This in particular, the biomechanics of the rider on the bike I think is very little understood in mountain biking. I hope to bring my expertise in this area to help riders select frame geometry and gear ratios that will allow them to enhance their skills and best apply their fitness when riding their favourite terrain on a custom Sharratt frame.

One of the key features of this frame is the pivot at the rear dropout which uses a dual bushing arrangement. Basically it is two sets of bushings, one in front of the other. One is the centre of rotation, the other uses a small eccentric pin to allow the required 1.4 degrees of movement and is there purely to stiffen up the rear end. The bushings contact laser-cut stainless plates so it is all very durable. It brings so much more rigidity to the rear end, so much so that now I want to change the dropout design to make it even stiffer again.

Who is the bike marketed at? (type of rider etc) The trail rider who is looking for a high performing frame and who values the fact that the bike can be tailored for them in terms of geometry, fit, components and colour.

When do you expect the first production bike(s) to roll off the line? Later in summer 2013.

You are off to Eurobike? When, and what do you hope to achieve from the visit? I am not this year however the bike will be displayed at the Lupine lights booth as they were really excited to display a bike alongside their lights that fitted in with their uncompromising manufacturing philosophy. We felt it was a bit early to have our own space at Eurobike this year. Lupine make the world’s premiere night lights and at the Eurobike show they are located amongst many high end German component and bike brands so we are expecting to get a gauge of public opinion on the bike.

The Sharratt bike will be distributed by Bikecycle, for more info or to put in an advanced order check out their site here and their Facebook here...