Building a new Bantam Pre-65 (Frame) by Rob Sloggett


Started on March 13, 2018 at 7:00 PM



This started off quite nicely. A facebook chat message from Mark Newman who had a couple of frames to sale really kickstarted the project.

13/3/18

This week has been a great start with Mark getting in contact regarding a Bantam frame and a pair of Villiers and James frames. A good chat on line with Mark reassured me that the marque of the frame did not necessariy tie me into having to find that specific engine although he may also have had a lead on a Viliers engine I could use.

I had been looking at a Bantam as my chosen route and Ebay had a D14 frame and engine for sale for around the £500 mark but it looked a bit of a mess and did not fill me with confidence. Mark also had a Bantam frame so I was definately going in the right direction. At this stage I had absolutly no idea on the geometry and modifications needed but read some good articles online that steered me away from a couple of routes I was considering. I had a budget in mind and knew that if I could find the right contact, a bespoke build was the right option.

At this point in time I was reading up on the regs regarding Pre 65 (as I am wanting to build the bike with a long term view that if I ever wanted to have a go at a national event, the bike was eligable). The phrase "must be in keeping with the original sillouete" seemes to be the main piece of guidance. I found this quite vague as I assume this lend's it open to people making complete frames out of lighterweight tubing?

A number of names cropped up and Andy Morgan regulary surfaced up as being highly recommended. Also at this point I was starting to learn about some of the different main frame names (geometry etc) and after a chat with Andy Morgan who builds frames based on a Rob Homer bike, I was happy to commision the frame from him. Andy has been excellant, helping me understand the basis of the build and sourcing the original front loop for me. From this, he creates a custom subframe, swing arm, bash plate and other incidentals to create the basis of a strong centre to the bike.

At this point I have budgeted in some additions to the frame such as a side stand, footrests, chain tensioner and a final powder coat but am looking forward to picking up my frame from Andy once he gives me the nod.

08/04/18

Had a facebook message from Andy this week. The frame is completed and it looks an absolute corker! The image at the top of this page is a standard bantam frame I believe, and you can see from the picture below which is Andys frame, both the silhouette of the original front loop but also the modifications to the lower part of the loop to accommodate the sump guard, the subframe where the mudguard loop now rides up and obviously the swing arm. Now I know my starting point, the budget has been recut to add quite a bit to the frame. Whilst not expensive, it is quite surprising the bits you don't realise make up the core frame fabric:

  • Footrests - £60
  • Sidestand - £50
  • Chain tensioner - £25
  • Chain guard - £25
  • Rear brake pedal - £35
  • Additions total = £195 (plus £120 for powder coating)

I had already budgeted to have the frame powder coated and at the moment I am considering a nice textured anthracite which Wrexham Powder Coating are demonstrating but I am sure once I visit their premises, other colours will jump out. Of course yellow is my favorite colour but I cant picture the Bantam in that yet.

 

I will keep this page updated as the frame build progresses.

09/07/18

I am certainly learning why some people "buy and not build". Last week I decided to start sourcing the steering head bearings and started off with a few pieces of information. Firstly from what I can read, the upper and lower races are different sizes and are Imperial. Secondly, they are hard to source and finally the stantion on my yokeset is to narrow for the stock quoted bearings (and is metric). The bearings are loose ball bearings which drop into a bearing race that press fits into the frame which I believe is a pain when fitting the underside one. After measuring the inner and outer diameters as well as the depth of the recess it became apparent that the two recesses in my headstock are the same size (not different as commonly cited).

Next I have the dilema that either way something is having to be modified so do I look for taper bearings that will fit or have a spacer machined to take a smaller taper bearing. With the bearings being reasonably cheap, I have deceided to order a set of originals which are 47.625mm OD and 27mm ID from Rex Caunt. My stantion is 24mm so if I go this route I will need to get a new stantion machined (the current one is too long anyway so it will need modifying). The other option is to go for a set of 41mm OD, 24mm ID tapered bearings and have a sleeve to take up the 6mm difference. The problem with these is that they are 12.5mm deep and the frame recess is only 9mm. At £10 a pair it might be worthwhile getting a set as a second option. A few people have mentioned sleeving down the headstock to take taper bearings so it seems like its not uncommon.

As you can see, what seems a simple task (get some headstock bearings and offer up the yoke) is turning into a task that will need some modification. Whichever way I go, I need to do it in a way that can be maintained going forward. I will let you know which way I go later on....

13/5/19

<insert what Jim did>


Frame Breakdown

Budget = £730

Spend to date = £567

broken down as

Doner frame and modifications = £535

Steering head bearings = £32