So how am i going to fix the frame to the rear axle? This is an important question on a number of levels.... Not least the fact that it is critical to the safety and handling.... but almost as important in as much that so many trike builders seem to make such a pigs ear of their project at this point.
Clearly the easiest approach would be to use the existing mountings on the axle itself (leaf spring mounts and shock-absorber mounts). Im not convinced however that this is the most beautiful solution - the spring mounts are too far outboard for me - i really want to keep the rear end clean and spindley and to do this i need to keep the frame as close to the centerline as i dare go while ensuring i keep an adequate degree of rigidity in the construction. Once again the position that Reliant gifted me with for the shock-absorber mounts aren't ideal (in my eyes).
Kev at projex uses the method shown in the top of the attached sketch - and i must say i rather like this - it would allow me to create a torsional rigidity (to handle all that power that a reliant engine drives through that performance differential) and keep the lines of the frame neat and tidy. This solution would mean that i would need to pay someone to do some engineering for me to make the clamp blocks.
Hughie, always looking out for my budget, wondered if i might be able to fabricate my own (and avoid the engineering costs) clamp blocks - similar to the idea in the lower part of the sketch (perhaps out of fabricated flat, tube and/or box sections). My concern here is that i dont want to be spending my time fabricating components when i should be fabricating the frame itself. I am sure there are other ways of executing this, and i shall postup some other sketches shortly
3 comments:
I would be a little concerned with the simple clamping idea as you have shown it. It would have to be sufficiently tight to resist the acceleration and deceleration torques. Since the outside of the rear axle tube is not going to be machined I think it will be difficult to ensure a reliable clamping system. The sketch you show of Kev's idea implies that the rear half clamp is welded to the axle whilst the front half is welded to the frame tubes. If this is the case I like this more as the weld will provide most of the restraining force assisted by the clamping of the two halves. This of course implies that you are prepared to weld to the axle, if this is the case then you can design the attachments more or less as you like.
I like the idea of having the lights at the end of the tubes. It would mean that their (and therefore the position of the tubes) would have to comply with the regulations. This may take the tubes too far towards the outside of the bike, back to the spring mounts. This doesn't of course apply if you fit the flame throwers, that invokes health and safety only!
I think that Tim and TVOR are worrying too much about torque. With the low budget home built clamp you can drill a small hole, say 6 mm dia, in one half of the clamp that corresponds, when assembled, with a small 6mm stud or spigot welded to the back axle. When the two halves of the clamp are bolted together, the spigot will engage in the locating hole and prevent any torque induced axle rotation within the clamps(or indeed any force trying to slide the exle longitudionally in the clamps, ie from side to side). It will work and remember Tim, only £300 quid left!!!
I like "Anon's" stud idea,a neat solution. It would certainly work as it would be in shear. Imagine trying to cut it off with a chisel. It would need to fit well to ensure that it remained in shear. My concern would be that you will end up with a fillet of weld round the stud which would make it difficult to get a good fit in the clamp bracket.
You could overcome this by firstly welding the stud to the axel and then fitting a short length of tube over the stud (suitably fitted at the fillet weld) and welding the tube to the end of the stud. This would give you a clean interface at the point where the stud/tube meets the axel.
I guess I am just worrying over much. It would be nice to drill a 6mm hole into the axel tube and weld the stud into the clamp from the outside. This would ensure a good fit between stud and clamp. The problem is that this might allow swarf to get inside the axel casing - not a good idea!
Good luck with your deliberations.
Post a Comment