Mid-engined-rat-rod-racer MERRR! [2016 Build-Off Entry]

Mower project 1 2016

Mid Engined Rat Rod Racer - MERRR!







The observant of you will have spotted this in last year’s build off. What with getting married and organising the wedding, life (happily) got in the way and I was unable to finish. So I really hope I can re-enter this year. Whilst I have started this project I would estimate I am no more than about 20% into it. My mock up is deceptive, I have heaps of work to do! Please read all of my entry before making a decision re entry. I am happy to make a new chassis if this one is decided to be too advanced through the build. I have left the bits of box section off of old school tables in the photo 2 above. Still some gum stuck to some of them! I am also setting myself the finish date of 4th August as this is the weekend of the VW Whitenoise festival (A UK VW show me and my buds go to) I want it finished so I have uber cool personal transport to cruise the show on!



Base Mower - (Photo taken for last years build off)
Base mower is a Mountfield 5/25 which I bought off ebay for £12.50! Like the black one in the background. It was complete apart from the cutting deck. Front wheels had been replaced with some weird looking solid tyred wheels at some point. I won’t be keeping many of the original moving parts of this mower. It’s mostly for a bodywork donor, steering wheel and pedal. Maybe one or two other bits. I will probably use the pressed seat pan for shows and a padded one (off of the black mower)for field use as I want to be kind on my ar$e! I plan to make the frame for the seat out of some chrome tubing I have (old chairs from work) Steering wheel I’m not sure about. I like the look of the original, but I don’t think it’ll take much abuse. So might get a kart one for field use.









Chassis/Steering
This is a ladder frame with rear outriggers for the rear axle bearings. This is currently tack welded so any alterations will be easier. The front axle is a sort of hot rod style currently tack welded. I have a pair of kart uprights. I will (probably) be experimenting with steering geometry quite a bit with this as I will be using a solid rear axle. The front wheels used to live under the pressed chassis this mower will be slammed! The front axle is widened and moved forward to allow the front wheels clearance to steer. I will not be moving where the steering column is on the existing chassis so will be engineering a linkage (I plan to use chain and sprockets) to allow the steering to work with the new axle position. I have the sprockets, chain and ball bearings for this.



Brakes
These will be hydraulic and acting on twin 5 inch mini moto (pocket bike) discs on the rear axle. I may go to larger discs as I think these might be a little small. We’ll see! I have made some disc carriers on my lathe from aluminium. The master cylinders/callipers are new items designed for a pit bike. Not used hydraulic brakes on a mower before and will hopefully stop it better than the cable brake on my red hot rod mower!



Drivetrain
I will be using a solid axle which I have made (needs further work cutting keyways/method of holding wheels on) myself. I need to learn how to use the milling head on my Clarke mill/lathe first/as I go! I have already machined the ends of the axle from 25mm to 20mm to allow the wheels to fit. I have a 41T rear sprocket which will run off a 10T on a jackshaft. I have a Chinese torque convertor (similar to a Comet I think?). Not used a torque convertor before.







Wheels
Are alloy ‘split rims’ off of a mobility scooter. Tyres are 13 x 5 x 6. I think they look sick! I was thinking about widening these the other day by machining spacers which fit between the split rims. If I experiment with this it’ll be one of the last things I do as it is just really for aesthetics. Tyres are in pretty good nick so will be re using. I have a spare wheel as I got these in a set of 5 off ebay. I may  mount a spare on the bodywork somewhere, dunno yet.



Engine
I pondered on using one of the many Briggs vertical shaft engines I have for this and probably would have stuck with one if I had a spare peerless 700 gearbox. I only have spare foote boxes at the mo and my experience of them isn’t great and I can’t find many recommendations for them on line either. I decided to go with a horizontal shaft Honda clone 6.5hp. They are cheap, £80 odd for a new one, pretty much disposable at that price. Spares/tuning parts are very easy to find in the UK (they are popular engines to use in karting. I plan to leave it standard until I have the mower up and running. Then I will add: pulse pump as I will use the tank off last years entry rather than the gravity one supplied with the engine. I have an ali flywheel and advanced timing key larger carb jet, uprated valve springs, I’ll do some porting, de govern, new air filter and some sort of custom exhaust. I have a pair of chrome framed tubular chairs from work as pipe donor! These will also form the seat frame.







I'm really looking forward to this build! I don't have a wedding to organise this year so can devote more time and attention to the project than I could last year. Any opinion, help, advice etc would be much appreciated.

Dang, someone building a slammed RER mower, looks sweet. Are you painting it? I kinda dog the rust. Great choice of engine and clutch. Hope to see it finished, I'm sure it will.

Looks like it should handle pretty good with the extra width.

The bodywork is staying rusty and ratty. I've even kept the gnarly old rubber for the footboards. I want it as ratty as poss apart from the engine, wheels and any other new (ish) bits. I want this mower to go quick, go round corners pretty well and stop well. I spent a couple of hours building the subframe for the engine/jackshaft. Nothing to take a photo of yet, mostly head scratching today.

Only just seen this now. Fantastic idea! RERs look great lowered. What top speed are you shooting for?

them wheels though lol looks great i always loved the look of the old boxer rears lowered and going fast good luck!

Im liking those wheels.

Def keep the tins original colour like it is, looks sweet, ive never seen a blue mountfield before, thought they were all red? Any idea what that cvt is rated to hp wise?

I like the wheels too! I had no idea what they were off. I bought them off ebay. I then saw some on a mobility scooter a few weeks after. Keep an eye out for mobility scooter wheels as they are generally a little more interesting than the standard steelies one finds on a mower. The only thing is that in a set, they are all the same size. Not good if you're going for a 'tractor look'. That said I have found this style of wheel smaller than mine.
The CVT transmission doesn't have a supplied hp rating. It is a Chinese 'version' of a comet as far as I'm aware. the driver pulley has a diameter of 19mm and the driven 16mm, so I don't think they'd take any daft power through them.
As for colour of Mountfields, I have a red one too and the black one in the background looks like it's original colour was yellow? The silver one I'm building from is pretty old, the 5hp engine has a pressed steel fuel tank. I'm guessing at mid 80s or earlier as I have the engine from an 88 Murray(Mountfield) and it has a plastic tank.

Sweet thanks for the info, should be a nippy wee number alright happy building

So had a day in the shed and got a few nits sorted (fingers crossed!)



I cut a key way in my home made sprocket carrier on the lathe. I pre drilled half the hole before squaring it off.



Cutting a 40mm hole in the back plate. (This bit bolts to the sprocket and the round bit in the previous pic.)



The nearly finished article. I will either cut these bolts or get some shorter ones before putting any power through it. It's not the prettiest thing in the world, but I made it with bits I already had. Making one is much more satisfying than buying one!

So the drive train has been a bit of a head scratcher. Originally I wanted to use a CVT which had a nice alloy back plate with integral bearings. Unfortunately I couldn't get this anywhere near fitting as it would have been much easier. I would have had to mount the engine higher and further back than I wanted. I will use the alloy backed CVT in a future project. I purchased another set of CVT pulleys for this project.



This was my first attempt using some hefty cast iron bearings. Nice having the chain out of the way.



This left the drive belt perilously close to the axle. Bit too close for comfort!



As were the sprockets!

So this is the third attempt. Fingers crossed it'll work. Any feedback/opinion would be appreciated as I'm new to the world of CVTs. I used a pair of much smaller pillow block bearings which I think are cast zinc. (Dunno if I trust them/bit skinny looking) We'll see when I pop a little power through it!







I've left all the steel which holds the bearings long at the mo as it may also fuction as a bodywork support as yet.

Looks like you got a fair wee bit done! Bearing/ CVT setup looks good. I think it should hold up. Only one way to find out though.

Update time! Not the most interesting of updates really but defo steps forward

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So I thought the outriggers were too big. Would have worked fine but didn't look right. Above is before. Below is after.

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I also drilled and bolted the jackshaft bearings.

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And have now made some more of the chassis/engine subframe a little more permanent. Not my best welding, the wire seemed to be sticking and not coming out steadily. A new tip seemed to help. My cheap Clarke mig is now 17 years old! It just keeps going though!

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So the engine is pretty much mounted in it's hopefully final resting place and it's not all held together with G clamps! As I  said at the beginning, not very exciting, but all necessary.

Outriggers definitely look better like that. What kind of speed are you hoping for? I think she'll turn heads anywhere!

Hi agains folks, aint been on here in ages, had a daft busy few months, but have recently pulled the MERRR out of the corner and am currently working on the steering. Some things which have been keeping me busy (along with work and life in gereral) are:

Recomissioning this,




This is my motorised table for two which I made for my wedding last year, the wife and I call it the 'wedding buggy'. It's made from a mobility scooter, bits of an old cycle, some old dining chairs, a mower steering gear and other bits and bobs. It cost me zero pounds apart from consumables, everything was donated! It was great fun at the recent VW Whitenoise festival me and my friends and wife went to. Really got us noticed!

I was also given this by the local vicars husband. No idea what I'll do with it yet? Any ideas? I'm thinking 4wd maybe. Rather twitchy steering, not ripe for a speed machine conversion!



Building this hen house and run also took up more than a few weekends!



My next posts will contain some actual 'mower building meat'! Gonna do them in small bursts as my PC keeps crashing/freezing when I have photobucket open.

So dragged the MERRR out of the corner where it had been used as an extra shelf/storage area. Did lots of head scratching, trying to remember what I'd planned to do with various bits, couldn't remember, so have been making it up as I go along (best way, but not what I tell the kids at school!)



So started to cut the bodywork to fit around the CVT. I think I'll have to trim a little more off once I have decided how I will mount the seat. It needs some sort of frame.



Rear bodywork sitting pretty level.

Machining the steering arm. The front steering arm has really had me scratching my head as to how I'm going to do it. I want to retain the hot rod style forward mounted axle, but also want to keep the original steering column location. The idea is to link with two sprockets and chain. What with the various angles of uprights, original column and my steering arm (a sort of steering jack shaft I guess), it has been a real challenge. Which I love of course, it'd be no fun if it was too easy!



So this is my steering jack shaft, the triangle bearing holder (under the g clamps) is nw welded. A sprocket will be attached at the bottom and carry a chain linked to the bottom of the steering column. Its quite low to the ground, so I think I may build some sort of 'sump guard' to protect. The rose joint on the top is the best bearing arrangment I found. I have considered so many different methods of steering force transfer - pinion gears, UJ, levers, chain & sprocket, about 10 billion!



So this is what I'm (the lathe) machining currently, as I write. The steering column. I've had to take this down from 20mm bar to 15mm for the bearings and the end needs to be 14mm to match the sprocket centre. It's on its final pass now.

So, progress made today, no major visual changes, but I'm pleased with how I got on. I used the milling head on my lathe for the first time today. I am two cuts for shaft keyways complete out of a total of 8 and I only broke two end mill cutters! here's my first little one on the end of the steering column.



The finished end in close up.



I also found time to drill holes/bolt the lower bearing/and cloumn support bracket in place. It spins really nicely, unnecessarily nicely tbh!



Here is my second keyway cut on the jack shaft. Not so pleased with this one, it went a little wobbly at one end of the groove. It'll work fine however and I'm pleased I've had success with cutting keyways on a shaft. Hopefully my next ones'll be even better. If you have any tips on milling I'm all ears. I'm pretty much making it up as I go with a little help from youtube.

oops, forgot this!

Milling is pretty simple, you take alittle off at a time in layers in multiple passes, forcing the bit into the metal is a nono. You want to cut into the metal when you are moving with only part of the end mill, if end mill is the cut size then multiple passes. Oil helps alot to cool the bit or end mill and keeping it sharp. You feel the controls when doing it because the controls tell you how hard the bit or end mill is cutting and will also tell you when the bit or end mill is going to break.

Looking good Jonny! I love the wedding buggy! When I saw that Stiga, the first thing that came into my head was a lifted 4x4 monster mower.