Hard Use: Some Monster Truck Repairs

[Paul-in-Plymouth]

Whenever one of my grandkids reaches age 3 or 4, I like to make them a monster truck after a design Les Neufield published in his book “Tremendous Toy Trucks.”  I like the look of Neufield’s truck designs. They’re straight-forward, not cartoonish, and they’re not overly detailed. They’re definitely toys, not models.  At the same time, they have an authentic air that seems to capture the essence.  They look rugged, and they invite vigorous play.  

  
When I made the first one (pictured, jatoba fenders and running boards), I followed Neufield’s design closely, except for strengthening the drive-shaft assembly.  

 
I  captured the ends of the drive-shafts in sockets rather than simply gluing them on.  This was facilitated by changing the triangle geometry from (30º, 60º, 90º) to (22.5º, 67.5º, 90º). 
 
 Three years later, the truck came back to my shop for repairs.  One of my grandson’s friends tried to ride it down the stairs like a skateboard: front bumper and both axle-blocks broken.  (Reports are that the friend survived the crash unscathed, as did the captured drive-shaft assembly.) 


The damage occurred at obvious points of stress-concentration.  Granted, bumping down the back steps with a 7-year-old aboard might stretch the range of intended uses a bit, but I took the opportunity to strengthen the new front-bumper yoke by reducing the bottom bevel at the front and by adding a 1/4”-radius on inside angles, leaving a web in each corner, as in this example:   
 

For the hard-maple axle-blocks, I first glued the pieces back together in place.  Then I reinforced them with 1/4” oak dowels running vertical across the split.  I returned it to Grandson #1 for further testing.  No more problems with that truck.

Since then I’ve made more trucks for more grandsons.  I included webs on the interior corners, and I captured the drive shafts; I didn’t bother with the cross-grain reinforcement.  All went well for couple more years.  


Recently, however, Grandson #2 broke his front axle-block “going over a jump.”  As shown, the split starts on the front side, a short distance into the wedge-shaped gusset that buttresses the axle-block.  It exits on the backside where the block emerges from the gusset.   


The repair, once again, was to glue the broken pieces back together in place and then insert a pair of 1/4 oak dowels cross-grain.  This time I made a fixture to clamp the truck upside-down for repairs.  

 

The small flush-cut saw from Lee Valley allows trimming the dowels between the wheels.  


This truck (purpleheart bumpers and running boards) is now back in service for Grandson #2.    

I have a few more trucks to make now.  I’ve learned my lesson and will add all the ruggedizing features noted above when I build them.  However, I’ll keep the clamping fixture around, just in case.

[Stwood_]

Good job. You put a lot of effort into those.

[MichaelS]

Awesome truck, and superb construction to have survived as well as it did with a boy on top. I am curious whether said boy will be amazed, indifferent, or tempted to try again when truck returns however - lol.

Good job and sharp looking repair (not to mention, engineered more robustly!)

Michael

[Steve N]

You have my vote for November 2016 Grampa of the month award winner

[daddo]

Kids can break things other humans can't. If it were made of solid steel- they would break it.

[AHill]

Way cool.

[MauleSkinner]

Good to see you've got the Unlimited Lifetime Parts and Labor Warranty...if they don't already, the kids will really appreciate that at some point in their lives.

[Paul-in-Plymouth]

Thanks to all for the kind words.  Both the boys whose trucks broke were upset when it happened and concerned I’d be disappointed or angry.  I perceived no disrespect in the damage, only boyish exhuberance, 

I took the opportunity to demonstrate to them the idea that things can be fixed, and often fixed better than they were originally.  (At least, that some things can be fixed.)  This is a mindset I learned from my father and later from my father-in-law, who both got very good at fixing things during the Great Depression.  I like to think it’s worth passing on.

As to what might happen next, who knows?  As I said, I’ll keep the clamping fixture around.

[BrokenOlMarine]

Great looking truck. Bet they are responsible for thousands of smiles per hour.